Brenner and Rector's The Kidney, 8th ed.

CHAPTER 28. Interventional Nephrology

Ivan D. Maya Michael Allon Souheil Saddekni David G. Warnock

		Overview of Vascular Access for Dialysis, 915
		Rationale for Interventional Nephrology, 915
		Radiation and Personal Safety, 916
		Procedures Involving Arteriovenous Grafts, 916
		Surveillance for Graft Stenosis, 916
		Angioplasty of Graft Stenosis, 919
		Thrombectomy of Grafts, 920
		Deployment of Stents for Graft Stenosis/Thrombosis, 923
		Procedures Involving Arteriovenous Fistulas, 923
		Preoperative Vascular Mapping, 923
		Salvage of Immature Fistulas, 925
		Percutaneous Mechanical Thrombectomy and Thrombolysis of Arteriovenous Fistulas, 928
		Novel Techniques for Treatment of Severe Stenotic Lesions, 929
		Cutting Balloon, 929
		Cryoplasty Balloon, 930
		Central Vein Stenosis, 930
		Indwelling Hemodialysis Catheters, 930
		Nontunneled Temporary Hemodialysis Catheters, 930
		Tunneled Hemodialysis Catheters, 932
		Less Common Locations for Tunneled Hemodialysis Catheters, 932
		Exchange of Tunneled Hemodialysis Catheters, 933
		Subcutaneous Hemodialysis Ports, 934
		Peritoneal Dialysis Catheter Procedures, 935
		Percutaneous Renal Biopsy, 936

OVERVIEW OF VASCULAR ACCESS FOR DIALYSIS

Most patients with end-stage renal disease undergo hemodialysis thrice weekly to optimize their survival, minimize medical complications, and enhance their quality of life. A reliable vascular access is a critical requirement for providing adequate hemodialysis. The ideal vascular access would be easy to place, be ready to use as soon as it is placed, deliver high blood flows indefinitely, and be free of complications. None of the existing types of vascular access achieves this ideal. Among the three types of vascular access currently available, native arteriovenous (AV) fistulas are superior to AV grafts, which, in turn, are superior to dialysis catheters. Recognizing the relative merits of the vascular access types, the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines recommend placement of AV fistulas in at least 50% of hemodialysis patients, AV grafts in 40%, and dialysis catheters in no more than 10%.^[1] The actual current distribution of vascular accesses among prevalent hemodialysis patients in the United States is 25% to 30% fistulas, 45% to 50% grafts, and 25% dialysis catheters. ^{[2] [3]}

Vascular access procedures and their subsequent complications represent a major cause of morbidity, hospitalization, and cost for chronic hemodialysis patients. ^{[4] [5] [6] [7] [8]} Over 20% of hospitalizations in hemodialysis patients in the United States are access related, and the annual cost of access morbidity is close to $1 billion.^[7] AV grafts are prone to recurrent stenosis and thrombosis and require multiple radiologic or surgical interventions to ensure their long-term patency for dialysis. Fistulas have a much lower incidence of stenosis and thrombosis than grafts do and require a much lower frequency of interventions to maintain their long-term patency for dialysis. ^{[7] [8] [9]}Conversely, fistulas have a higher primary failure rate (fistulas that never become usable for dialysis) than grafts do. Tunneled dialysis catheters have the highest frequency of infection and thrombosis but are a necessary evil, either as a bridge device in patients waiting for a fistula or graft or as an access of last resort in patients who have exhausted all options for a permanent vascular access. ^{[10] [11]} Compared with patients who continue to dialyze with catheters, those who switch from a catheter to a fistula or graft have a substantially lower mortality risk.^[12]

Even with aggressive efforts to follow the K/DOQI guideline on vascular access, it is likely that all three types of vascular access will remain in use for the foreseeable future. Much more clinical research is necessary to learn how to minimize the complications and optimize the outcomes of each type of vascular access.

RATIONALE FOR INTERVENTIONAL NEPHROLOGY

Patients with stage 4 chronic kidney disease are regularly seen by their nephrologists and referred to different subspecialists, including vascular surgeons and interventional radiologists, for access placement for hemodialysis or peritoneal dialysis. Once these patients start their dialysis treatments, vascular access becomes a very important aspect of their care. The patients undergo frequent placement of temporary or tunneled hemodialysis catheters, revision of a permanent access, surgical or percutaneous thrombectomies, and other related endovascular procedures. For a long time, nephrologists have taken a passive role in this very complicated but important area of dialysis care. However, nephrologists who were interested in improving the quality and timely provision of these services have developed a growing interest in having such procedures performed by appropriately trained nephrologists.^[13]

During the last decade, some nephrologists have become directly motivated in providing access procedures for their patients. This initiative was pioneered by Gerald Beathard^[14] and subsequently adopted by nephrologists at other medical centers. ^{[15] [16] [17] [18] [19] [20]} It is not uncommon at present to find well-trained nephrologists getting actively involved in performing the various imaging and interventional dialysis procedures. Depending on the degree and depth of their training, interventional nephrologists can provide ultrasound and biopsy of kidneys, vascular mapping before access surgery, and continued involvement after surgery by providing procedures necessary for the maintenance of long-term patency of the vascular access. A decrease in hospitalizations for vascular access-related complications and missed outpatient hemodialysis sessions has been documented at one dialysis center when nephrologists performed interventional access procedures.^[20]

In 2000, a group of physicians, including nephrologists and radiologists, formed the American Society of Diagnostic and Interventional Nephrology (ASDIN). This organization provides certification to interventional nephrologists as well as accreditation to the institutions involved in the practice and teaching of interventional procedures in the nephrology specialty.^[18] Certification and accreditation are given for diagnostic ultrasound, peritoneal dialysis insertion, and endovascular procedures on AV fistulas, grafts, and chronic central venous catheters for dialysis. Comprehensive training is required to achieve dexterity and knowledge. Several academic centers in the United States already have interventional nephrology programs in place, either in a freestanding interventional facility or in a hospital-based radiology suite. A comprehensive list of procedures performed by interventional nephrologists is provided in Table 28-1 .

TABLE 28-1 -- Procedures Performed by Interventional Nephrologists

Diagnostic renal ultrasound

Ultrasound guided percutaneous renal biopsy

Placement of nontunneled and tunneled dialysis catheters

Exchange of tunneled dialysis catheters

Implantation of subcutaneous dialysis devices

Preoperative vascular mapping

Surveillance for stenosis

Diagnostic fistulograms of arterio-venous grafts and fistulas

Angioplasty of peripheral and central venous stenosis

Deployment of endoluminal stents for peripheral and central venous stenosis

Mechanical thrombectomy of arterio-venous grafts and fistulas

Sonographic or angiographic assessment of immature fistulas

Salvage procedures for immature fistulas

Placement of peritoneal dialysis catheters

A given interventional nephrology program may provide only a subset of these procedures, depending on the local needs and arrangements with other medical subspecialties. A solo nephrologist may decide to perform selected procedures necessary to provide an immediate dialysis access (such as insertion of dialysis catheters), thus eliminating delays resulting from scheduling difficulties. Conversely, a nephrology group practice may designate one or two nephrologists to be fully trained to perform a spectrum of interventional procedures.

At University of Alabama at Birmingham (UAB), a unique multidisciplinary model has been adopted to the patients' best advantage. This model consists of a joint interventional radiology/nephrology program, with interventional nephrologists and interventional radiologists sharing the same radiology suites, and working side by side to perform all dialysis access procedures. This program draws its success by using all existing technical, clinical, imaging, and surgical talents at the same institution.

A key element of any successful interventional program, whether it involves radiologists or nephrologists, is to have actively involved nephrology and dialysis program directors tracking the outcomes of the procedures and implementing timely quality improvement initiatives to improve outcomes. This can be best accomplished by having dedicated vascular access coordinators who maintain prospective, computerized records of all access procedures performed.^[21]

RADIATION AND PERSONAL SAFETY

The understanding of basic radiation safety is very important to protect the patient, the physician, and the staff involved in the care of the patient. Unnecessary radiation exposure is harmful and can be easily prevented. The U.S. Food and Drug Administration (FDA) oversees the rules and regulations for use of x-ray equipment. The U.S. Occupational Safety and Health Administration (OSHA) regulates the radiation exposure of workers. Each state has its own regulatory office to ensure that workers do not exceed a predetermined radiation dose.

Exposure is the amount of ionizing radiation reaching a subject, and it is measured in units of Roentgen. The amount of energy absorbed by a material when it is exposed to ionizing radiation is measured in rads. The absorbed dose is always lower than the exposure, because the tissue does not absorb all the energy from the radiation. An absorbed dose equivalent is used to relate the amount of biologic damage and is measured in rem. The OSHA occupational dose limit for the whole body is 1.25 rem/quarter; for the extremities, it is 18.75 rem/quarter. A dosimeter must be worn at all times on the outside of the lead apron, and the absorbed dose measured monthly. To protect against radiation, the interventionist should minimize the time of exposure to radiation, minimize the use of magnification imaging, properly use collimators and field filters, maximize the distance between the source of radiation and the personnel involved with the procedure, minimize the use of cineangiography and continuous fluoroscopy, and use proper shielding, including lead aprons, thyroid collars, leaded glasses, and lead shields.

Knowledge of these facts and application of appropriate safeguards are particularly important in dialysis access procedures, especially those involving vascular access interventions in the upper extremity. The operators' proximity to the x-ray tube and difficulty in shielding increases their radiation exposure

PROCEDURES INVOLVING ARTERIOVENOUS GRAFTS

Surveillance for Graft Stenosis

About 80% of graft failures are due to thrombosis, whereas 20% are due to infection. ^{[22] [23]} Thus, improving graft longevity requires implementing measures to reduce the frequency of graft thrombosis. When grafts are referred for thrombectomy, a significant underlying stenosis is observed, most commonly at the venous anastomosis, the draining vein, or the central veins. ^{[24] [25] [26]} This observation suggests that prophylactic angioplasty of hemodynamically significant graft stenosis may reduce the frequency of graft thrombosis, and thereby increase cumulative graft survival.

A seminal study by Schwab and co-workers^[27] was the first to provide evidence supporting this approach. This group of investigators performed measurements of dynamic dialysis venous pressures during consecutive hemodialysis sessions under carefully standardized conditions. They discovered that a persistent elevation in the dialysis venous pressure measured at a low dialysis blood flow was predictive of hemodynamically significant stenosis. The investigators then instituted a program of clinical monitoring for graft stenosis, with referral for prophylactic angioplasty if there was a suspicion of graft stenosis. Compared with the historical control period, a regimen of stenosis monitoring and prophylactic angioplasty reduced the frequency of graft thrombosis by about two thirds, from 0.6 to 0.2 events per year. This landmark study stimulated a large volume of subsequent clinical research directed at two fundamental issues: (1) identifying a variety of noninvasive methods to screen for graft stenosis and (2) evaluating whether stenosis surveillance and prophylactic angioplasty improved graft outcomes.

A variety of methods have been validated for detection of hemodynamically significant graft stenosis ( Table 28-2 ). Clinical monitoring consists of using information that is readily available from physical examination of the AV graft, abnormalities experienced during the dialysis sessions (difficult cannulation or prolonged bleeding from the needle puncture sites), or unexplained decreases in the dose of dialysis (Kt/V). ^{[24] [25] [28]} Graft surveillance uses noninvasive tests requiring specialized equipment or technician training that are not obtained as part of the routine dialysis treatment. These include measurement of static dialysis venous pressure (normalized for the systemic pressure), ^{[29] [30]} measurement of the access blood flow, ^{[31] [32] [33] [34]} or duplex ultrasound to evaluate directly for evidence of stenosis. ^{[35] [36] [37] [38]} Each of these monitoring or surveillance tools has been reported to have a positive predictive value for graft stenosis between 70% and 100% ( Table 28-3 ). The negative predictive value has not been studied systematically, as it would require obtaining routine fistulograms in patients whose screening test is negative. However, it can be inferred from the proportion of graft thromboses not preceded by abnormalities of graft surveillance (∼25%).^[34]

TABLE 28-2 -- Methods of Stenosis Monitoring

Clinical monitoring

Physical examination (abnormal bruit, absent thrill, distal edema) Dialysis abnormalities (prolonged bleeding from needle sites, difficult cannulation) Unexplained decrease in Kt/V

Surveillance

Static dialysis venous pressure (adjusted for systemic pressure) Access blood flow Qa < 600 mL/min Qa decreased by > 25% from baseline Doppler ultrasound

Kt/V, dialysis dose; Qa, access blood flow.

TABLE 28-3 -- Positive Predictive Value of Monitoring Methods for Graft Stenosis

Surveillance Method	Measurements (N)	Positive Predictive Value (%)
Clinical monitoring
Cayco et al, 1998[41]	68	93
Robbin et al, 1998[37]	38	89
Safa et al, 1996[28]	106	92
Maya et al, 2004[25]	358	69
Robbin et al, 2006[38]	151	70
Static venous pressure
Besarab et al, 1995[29]	87	92
Flow monitoring
Schwab, 2001[48]	35	100
Moist et al, 2003[45]	53	87
Ultrasound
Robbin et al, 2006[38]	122	80

In contrast, the predictive value of these surveillance methods for graft thrombosis is much less impressive. Thus, when grafts with abnormal monitoring criteria suggestive of stenosis are observed without preemptive angioplasty, only about 40% of the grafts clot over the next 3 months. ^{[39] [40]} In practice, this means that in any program of graft monitoring, about half of the preemptive angioplasties that are performed are superfluous. Unfortunately, there are no reliable tests to distinguish between the subset of grafts with stenosis that will progress to thrombosis from those that will remain patent without any intervention.

Several observational studies have documented that introduction of a monitoring or surveillance program for graft stenosis with preemptive angioplasty lowered the frequency of graft thrombosis by 40% to 80%, compared with the historical control period during which there was no monitoring program ( Table 28-4 ). ^{[21] [27] [28] [29] [41] [42]} The promising findings from multiple observational studies have led to the K/DOQI recommendations of implementing a program of graft surveillance and preemptive angioplasty in all dialysis centers in order to reduce the frequency of graft thrombosis.^[1]

TABLE 28-4 -- Effect of Surveillance on Graft Thrombosis: Observational Studies

Reference	Surveillance Method	Thrombosis Rate (Per Graft-Yr)
		Historical Control	Surveillance Period	Reduction (%)
Schwab et al, 1989[27]	Dynamic dialysis venous pressure	0.61	0.20	67
Besarab et al, 1995[29]	Static dialysis venous pressure	0.50	0.28	64
Safa et al, 1996[28]	Clinical monitoring	0.48	0.17	64
Allon et al, 1998[21]	Clinical monitoring	0.70	0.28	60
Cayco et al, 1998[41]	Clinical monitoring	0.49	0.29	41
McCarley et al, 2001[42]	Flow monitoring	0.71	0.16	77

Only in the last few years has the value of graft stenosis surveillance been subjected to rigorous testing in randomized clinical trials. To date, there have been six such trials, evaluating surveillance with access flow monitoring, static dialysis venous pressure, or ultrasound ( Table 28-5 ). Only one of the six randomized trials has demonstrated a benefit of ultrasound graft surveillance^[35]; the other five studies were negative, despite a substantial increase in the frequency of preemptive angioplasty in the surveillance group. ^{[36] [38] [43] [44] [45]} For example, one study randomized patients with grafts to standard clinical monitoring alone or to a combination of clinical monitoring and ultrasound surveillance for stenosis. The patients in the ultrasound group underwent a 66% higher frequency of preemptive angioplasty, yet there was no difference between the two randomized groups in terms of frequency of graft thrombosis, time to first thrombosis, or likelihood of graft failure ( Fig. 28-1 ).^[38] Because the randomized studies have been relatively small in size, it is possible they were inadequately powered to detect a modest benefit of graft surveillance. A large-scale, multicenter study would be required to provide a definitive answer to this controversial question. In the meantime, the value of surveillance of graft stenosis and preemptive angioplasty in improving graft outcomes remains controversial. ^{[46] [47]}

TABLE 28-5 -- Randomized Clinical Trials of Graft Surveillance

Reference	Surveillance Method	Subjects (N)		PTA/Yr		Thromb-free Survival at 1 Yr		Cum Survival at 1 Yr
		Con	Surv	Con	Surv	Con	Surv	Con	Surv
Lumsden et al, 1997[173]	Doppler US	32	32	0	1.5	0.51	0.47	N/A	N/A
Ram et al, 2003[36]	Access flow	34	32	0.22	0.34	0.45	0.52	0.72	0.80
	Doppler US		35		0.65		0.70		0.80
Moist et al, 2003[45]	Access flow	53	59	0.61	0.93	0.74	0.67	0.83	0.83
Dember et al, 2004[43]	Static DVP	32	32	0.04	2.1	N/A	N/A	0.74	0.56
Malik et al, 2005[35]	Doppler US	92	97	N/A	N/A	N/A	N/A	0.73	0.93
Robbin et al, 2006[38]	Doppler US	61	65	0.64	1.06	0.57	0.63	0.83	0.85

Con, control; Cum, cumulative; DVP, dialysis venous pressure; N/A, not available; PTA, percutaneous transluminal angioplasty; Surv, surveillance; Thromb, thrombosis; US, ultrasound.

FIGURE 28-1 A, Comparison of cumulative graft survival between randomized patients with clinical monitoring versus clinical monitoring plus regular ultrasound surveillance of grafts. P = .93 by the log rank test. B, Comparison of thrombosis-free graft survival between randomized patients with clinical monitoring versus clinical monitoring plus regular ultrasound surveillance of grafts. P = .33 by the log rank test. (Reproduced from Robbin ML, Oser RF, Lee JY, et al: Randomized comparison of ultrasound surveillance and clinical monitoring on arteriovenous graft outcomes. Kidney Int 69:730–735, 2006.)

If underlying graft stenosis is an important predictor of graft thrombosis, why is preemptive angioplasty not more successful in reducing graft thrombosis? The fundamental problem appears to be the short-lived efficacy of angioplasty to relieve graft stenosis. When serial access blood flows have been used as a surrogate marker of successful angioplasty, 20% of grafts have recurrent stenosis within 1 week of angioplasty and 40% within 1 month of angioplasty. ^{[45] [48]} In another study, the mean access blood flow after angioplasty increased from 596 to 922 mL/min. However, 3 months later, the mean flow had decreased to 672 mL/min.^[49] In addition, there is published evidence suggesting that the injury from balloon angioplasty can actually accelerate myointimal hyperplasia, thereby resulting in recurrent stenosis.^[50] Not surprisingly, patients undergoing angioplasty for graft stenosis require frequent re-interventions owing to recurrent stenosis. The median intervention-free patency after graft stenosis is only about 6 months. ^{[24] [25]}

The pathophysiology of graft stenosis involves proliferation of vascular smooth muscle cells (myointimal hyperplasia), with progressive encroachment of the lesion into the graft lumen.^[51] To improve the patency of grafts after angioplasty, some investigators have attempted stent deployment. The rationale is that the rigid scaffold of the stent helps to keep the vascular lumen open. There has also been an ongoing interest in pharmacologic approaches to prevention of myointimal hyperplasia. Two small, single-center, randomized clinical trials have documented a beneficial effect of dipyridamole and fish oil in preventing graft thrombosis. ^{[52] [53]} A multi-center, randomized, double-blinded study compared clopidogrel plus aspirin with placebo for prevention of graft thrombosis. The study was terminated early owing to an excess of bleeding complications in the intervention group; there was no difference in the rate of graft thrombosis between the two randomized groups.^[54] The Dialysis Access Consortium (sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases [NIDDK]) is currently conducting a large, multicenter, randomized, double-blinded clinical trial to compare Aggrenox (long-acting dipyridamole + low-dose aspirin) with placebo in prevention of graft failure.^[55] Details of pharmacologic approaches to prophylaxis of graft stenosis and thrombosis are beyond the scope of this chapter.

Angioplasty of Graft Stenosis

As described in the previous section, patients with patent grafts are frequently referred for elective angioplasty when hemodynamically significant stenosis is detected either by clinical monitoring or by one of several methods of graft surveillance. The goal of elective angioplasty is to correct the stenotic lesion that impairs optimal delivery of dialysis and, hopefully, delay graft thrombosis. The most common location of the stenosis by angiography is the venous anastomosis, followed by the peripheral draining vein, central vein, and intragraft ( Table 28-6 ). Inflow (arterial anastomosis) stenosis has been rare (<5%) in most series. However, a recent study using retrograde angiography with manual occlusion of the venous limb documented an inflow stenosis in 29% of grafts referred for diagnostic angiography.^[56]

TABLE 28-6 -- Location of Stenosis in Patients with Grafts Undergoing Angioplasty

Reference	All Stenotic Lesions (%)
	VA	VO	CV	IG	AA
Beathard, 1992[26]	42	34	4	20	0
Lilly et al, 2001[24]	55	22	15	6	2.5
Elective PTA
Lilly et al, 2001[24]	60	14	9	10	7
Thrombectomy
Maya et al, 2004[25]	62	16	8	12	1.5

AA, arterial anastomosis; CV, central vein; IG, intragraft; PTA, percutaneous transluminal angioplasty; VA, venous anastomosis; VO, venous outflow.

A number of published series have documented the short-lived primary patency (time to next radiologic or surgical intervention) of grafts after elective angioplasty ( Table 28-7 ), with only 50% to 60% patent at 6 months and 30% to 40% at 1 year. This means that, on average, each graft requires two angioplasties per year. The primary patency is shorter after angioplasty of central vein stenosis compared with other stenotic locations. In one study, the primary patency at 6 months was only 29% for central vein stenosis compared with 67% for stenosis at the venous anastomosis.^[26] Most studies have documented progressively shorter patency after each consecutive angioplasty, although one investigator found comparable primary patency for the first and subsequent graft angioplasties.^[26]

TABLE 28-7 -- Primary Graft Patency After Elective Angioplasty

Reference	Procedures (N)	Primary Patency At
		3 Mo	6 Mo	12 Mo
Beathard, 1992[26]	536	79	61	38
Kanterman et al, 1995[174]	90		63	41
Safa et al, 1996[28]	90	70	47	16
Turmel-Rodrigues et al, 2000[92]	98	85	53	29
Lilly et al, 2001[24]	330	71	51	28
Maya et al, 2004[25]	155	79	52	31

The primary patency of AV grafts after elective angioplasty is not affected by patient age, race, diabetes, or peripheral vascular diseases.^[25] However, the patency is shorter in women than in men.^[25] The primary patency after angioplasty is also not influenced by the location of the graft or the number of concurrent stenotic lesions found.^[24]

The technical success of an angioplasty procedure may be assessed in several ways. The first is a visual inspection of the graft before and after the procedure to determine whether the magnitude (percent of stenosis relative to the normal vessel diameter) has been reduced. The degree of stenosis of each lesion can be quantified with calipers or graded semiquantitatively using the following scale: grade 1, no (<10%) stenosis; grade 2, mild (10%–49%) stenosis; grade 3, moderate (50%–69%) stenosis; and grade 4, severe (70%–99%) stenosis. ^{[24] [25]} A second approach is to measure the intragraft pressure before and after the procedure and normalize it for the systemic blood pressure. A third approach is to measure the change in access blood flow before and after the procedure. Each of these measures has been shown to be predictive of the primary patency of grafts after elective angioplasty. In one large series, after elective angioplasty, the median intervention-free survival of graft with no residual stenosis was 6.9 months compared with 4.6 months if there was any degree of residual stenosis.^[24] Similarly, the median primary patency of grafts after angioplasty was inversely proportional to the intragraft-to-systemic pressure ratio, being 7.6, 6.9, and 5.6 months, when this ratio was less than 0.4, 0.4 to 0.6, and greater than 0.6, respectively.^[24] Finally, a failure to significantly increase the access blood flow after angioplasty is observed in 20% of grafts at 1 week and in 40% by 1 month, ^{[45] [48]} confirming the short-lived benefit of this intervention.

Technical Procedure: Percutaneous Graft Angioplasty

The AV graft is accessed with a micropuncture single needle at the arterial limb of the graft toward the venous outflow. The needle is exchanged for a 4-French catheter. Digitally subtracted antegrade angiograms are taken through the catheter to visualize the venous limb of the graft, the draining vein and central vessels. After applying pressure to the venous outflow, a retrograde angiogram is performed to visualize the arterial anastomosis. The presence or absence of stenotic lesions and their number and location, arterial anastomosis, intragraft, venous anastomosis, draining vein and central vein are recorded. The degree of stenosis of each lesion is quantified with calipers or graded semiquantitatively. ^{[24] [25]} Lesions with at least 50% stenosis are considered to be hemodynamically significant and undergo angioplasty. If a stenotic lesion is encountered, then the 4-French catheter is exchanged for a 6-French sheath. An angioplasty balloon is introduced through the sheath. Balloon sizes (7–12 mm in diameter to 20-80 mm in length) vary depending on the vessel to be treated; usually the balloon is selected to be 1 mm larger than the size of the graft or the vessel to be treated. The balloon is placed at the level of the stenotic lesion and inflated to its nominal pressure for 30 to 90 seconds (Figs. 28-2 and 28-3 [2] [3]). The majority of anastomotic lesions require higher pressure than those required for peripheral arterial angioplasty. Therefore, high-pressure balloons with minimal burst pressure greater than 15 atm are routinely used.^[57] If a residual (>30%) stenosis is found, prolonged angioplasty (5-min inflation), higher-pressure balloons (≤30 atm), and occasionally, stent deployment may be required to treat these lesions. At UAB, the patient's intragraft pressure and systemic pressure are measured before and immediately after the intervention. In addition to angiographic findings, we rely on a reduction of intragraft-to-systemic pressure ratio to confirm technical success and hemodynamic improvement. Other centers rely on different criteria, such as increases in access flow rate.

FIGURE 28-2 A, Left upper arm arteriovenous (AV) graft angiogram shows a severe (95%) stenotic lesion at the level of the venous anastomosis. B, Left upper arm AV graft stenotic lesion at the venous anastomosis with the angioplasty balloon partially inflated. C, Left upper arm AV graft stenotic lesion at the venous anastomosis with the angioplasty balloon fully inflated. D, Final postangioplasty left upper arm AV graft angiogram shows a treated lesion with minimal residual stenosis.

FIGURE 28-3 A, Digital subtraction angiography (DSA) of a left upper arm AV graft shows a moderate stenotic lesion at the level of the arterial limb of the graft. B, Spot film shows the stenotic lesion being angioplastied. C, Final postangioplasty DSA shows excellent results.

The major complications of this procedure are vessel extravasations and rupture of the vessel after the angioplasty treatment. Deploying a covered stent (endograft) can treat these complications. Surgical repair is indicated if the rupture is not corrected by stent placement.

Thrombectomy of Grafts

The majority of graft failures are due to thrombosis, which occurs most commonly in the context of underlying stenosis at the venous anastomosis. ^{[23] [24]} For this reason, successful graft thrombectomy requires both resolution of the clot and correction of the underlying stenotic lesion. The primary patency of grafts after thrombectomy and angioplasty ( Table 28-8 ) ranges from 30% to 63% at 3 months and 11% to 39% at 6 months. These outcomes are considerably worse than the primary patency observed after elective angioplasty (see Table 28-7 ), which is 71% to 85% at 3 months and 47% to 63% at 6 months. The primary graft patency is similar for mechanical thrombectomy and pharmacomechanical thrombectomy.^[58] A large series comparing the outcomes of both types of radiologic procedures at one institution found that the primary patency was only 30% at 3 months for clotted grafts compared with 71% for patent grafts undergoing elective angioplasty ( Fig. 28-4A ).^[24] The discrepancy was still apparent when the analysis was restricted to the subset of procedures in which there was no residual stenosis, with a median primary patency of 2.5 months after thrombectomy compared with 6.9 months after elective angioplasty (see Fig. 28-4B ).^[24]

TABLE 28-8 -- Primary Graft Patency After Thrombectomy

		Primary Patency At
Reference	Procedures (N)	3 Mo	6 Mo
Valji et al, 1991[175]	121	53	34
Trerotola et al, 1994[176]	34	45	19
Beathard, 1994[58]	55 mech	37
	48 pharm	46
Cohen et al, 1994[177]	135	33	25
Sands et al, 1994[178]	71		11
Beathard, 1995[179]	425	50	33
Beathard et al, 1996[180]	1176	52	39
Trerotola et al, 1998[181]	112	40	25
Turmel-Rodrigues et al, 2000[92]	58	63	32
Lilly et al, 2001[24]	326	30	19

Mech, mechanical; pharm, pharmacomechanical.

FIGURE 28-4 A, Intervention-free graft survival following elective angioplasty (solid line) or thrombectomy + angioplasty (dotted line). Graft survival was calculated from the date of the initial intervention to the date of the next intervention (angioplasty, declot, or surgical revision). P < .001 for the comparison between the two groups. B, Intervention-free graft survival following elective angioplasty (circles) or thrombectomy + angioplasty (triangles) in the subset of procedures with no residual stenosis. Graft survival was calculated from the date of the initial intervention to the date of the next intervention (angioplasty, declot, or surgical revision). P < .001 for the comparison between the two groups. (Reproduced from Lilly RZ, Carlton D, Barker J, et al: Clinical predictors of A-V graft patency following radiologic intervention in hemodialysis patients. Am J Kidney Dis 37:945–953, 2001.)

The duration of graft patency after thrombectomy does not differ between diabetic and nondiabetic patients. It is also not affected by the graft location or the number of concurrent graft stenoses found.^[24] However, similar to the observations obtained after elective angioplasty, the primary patency of grafts after thrombectomy is inversely proportional to the magnitude of residual stenosis at the end of the procedure.^[24]

Technical Procedure: Percutaneous Graft Thrombectomy

The AV graft is initially accessed with a single-wall needle at level of the arterial limb of the graft. A glidewire is passed up to the venous outlet and the needle exchanged for a 6-French catheter sheath. A catheter is placed beyond the clotted graft, and a venogram is performed of the venous outflow and central circulation. Extreme caution is exercised not to pressure-inject contrast into the graft, because it can dislodge clot and cause arterial emboli. Because greater than 60% of the stenotic lesions are located at the venous anastomosis, an angioplasty balloon, usually 8 by 40 mm, is placed at that site and inflated to its nominal pressure (15 atm). The balloon is removed, and then a mechanical thrombectomy can be achieved by several methods including manual aspiration of the clots, infusion of a thrombolytic agent (tissue-type plasminogen activator [t-PA], urokinase), use of a clot-buster device (Angiojet, Arrow-Trerotola, Cragg thrombolytic brush, Hydrolyser, Prolumen, Amplatz thrombectomy device), or a combination of any of these ( Fig. 28-5 ). Pure mechanical thrombectomy is sufficient, and thrombolysis rarely necessary. The graft is accessed for a second time with a single-wall needle at the venous limb of the graft. The needle is exchanged over a wire for a 6-French catheter sheath. A glidewire is passed into the arterial circulation. A Fogarty balloon is passed beyond the arterial anastomosis and pulled back to dislodge the arterial plug. Aspiration of the clots through both sheaths is performed; the clot-bluster device is used again to clear all debris still in the graft. Once blood flow in the graft is restored, as assessed by physical examination, small amounts of contrast are injected to check for residual clots. Finally, antegrade and retrograde angiograms of the graft are performed to assess for patency and look for other stenotic lesions. Angioplasty of any residual hemodynamically significant stenotic lesion in the vascular access circuit is performed. Intra-access pressure and systemic pressure (measured inside the graft by occluding the venous outflow) are measured. The ratio is calculated to confirm acceptable angioplasty results. High intragraft pressures indicate residual venous anastomotic obstruction, whereas low pressures indicate obstruction at the arterial inflow.

FIGURE 28-5 A, Percutaneous mechanical thrombectomy: A left upper arm AV graft site is prepped and two 6-French sheaths are in place. B, Percutaneous mechanical thrombectomy: Spot film shows the use of a percutaneous thrombectomy device (PTD). (Arrow-Trerotola-PTD.)

Major complications of this procedure are vessel extravasations and rupture of the vein either because of wire manipulation or as a result of the angioplasty; stent deployment is the treatment of choice. Arterial emboli distal to the AV anastomosis may occur, and if encountered, either intervention or surgical embolectomy is required. One interventional method to treat this complication is back bleeding; which is simply an occlusion of the artery before its anastomosis to the graft, causing a retrograde blood flow that brings the clot into the graft. The use of a Fogarty balloon to remove the clot and the use of thrombolytics agents can also be performed to treat this complication.^[59]Pulmonary embolism is common (∼35%) in patients undergoing graft thrombectomy but is rarely of clinical significance.^[60]

Deployment of Stents for Graft Stenosis/Thrombosis

As mentioned previously, the primary patency of grafts after angioplasty is short-lived, and there is evidence that the vascular injury from angioplasty may actually accelerate myointimal hyperplasia.^[50] In view of these considerations, there has been considerable interest in technical modifications to improve the patency of grafts after angioplasty. Endoluminal stents work by forming a rigid scaffold preventing elastic recoil and helping to keep the vascular lumen open. Therefore, although myointimal hyperplasia recurs, it is less likely to narrow the vascular lumen. Stent placement has been attempted for the treatment for rapidly recurrent stenosis. A stenosis that is highly resistant to balloon angioplasty and cannot be expanded with a balloon is a contraindication for stent placement, because the stent will be as narrow as the original stenosis. On rare occasions, when trying to overcome such resistant stenoses with very high pressure, angioplasty may result in venous rupture and extravasation. Surgery is not necessary in these situations, as the complication can be converted to success by using stents or stent grafts (endograft).

Several small series have reported the outcomes after stent deployment for refractory vascular access stenosis. ^{[61] [62] [63] [64] [65] [66] [67]} Most of these studies have been limited by retrospective data collection, absence of a suitable control group, lumping together of patent and thrombosed accesses, and combining grafts with fistulas. A small randomized study comparing stents with conventional angioplasty found no difference in primary graft patency after the intervention.^[62] However, this study enrolled a mixture of clotted and patent grafts, and the stenotic lesions were at a variety of locations, thus limiting the interpretation of the findings.

Because primary graft patency is particularly short-lived in clotted grafts undergoing thrombectomy, those grafts may experience better patency after stent deployment. One series reported the outcomes of 34 clotted grafts undergoing thrombectomy with stent placement at the venous anastomosis.^[65] The primary patency after intervention in this homogeneous group of grafts was 63% at 6 months. Although there was no matched control group treated with angioplasty alone, the primary graft patency was much higher than that reported previously (11%–39% at 6 months) (see Table 28-8 ). A nonrandomized study comparing outcomes of clotted grafts treated with thrombectomy and stent placement at the venous anastomosis with matched control patients treated with only thrombectomy and angioplasty observed a significantly longer primary patency in grafts treated with a stent compared with those treated with angioplasty alone.^[68] A definitive, randomized clinical trial is warranted to evaluate whether the patency of grafts after thrombectomy is enhanced by stent deployment.

A number of stent types are available, including covered and noncovered stents and either balloon or self-expandable. However, there are no published clinical trials comparing the outcomes between stent types. It is also possible that the administration of antiplatelet agents after stent placement or employment of drug-eluting stents (Sirolimus) may further improve the primary patency of grafts after thrombectomy, but again, there is no literature available at this time. Clopidrogel, an antiplatelet agent, is prescribed routinely after coronary stent placement to decrease early rethrombosis. It is not known whether administration of clopidogrel would prolong primary patency after AV graft stent placement.

Technical Procedure: Percutaneous Deployment of Stents

Percutaneous mechanical thrombectomy is achieved as described in the previous section. If a severe elastic recoil is seen on the final angiogram or a very significant residual stenosis (>30%) is seen at the level of the original stenotic lesion, then a stent could be deployed.^[59] Stent sizes vary from 6 to 12 mm in diameter and 10 to 80 mm in length. The most commonly used stents are nitinol or nitinol covered with expanded polytetrafluoroethylene (e-PTFE). The appropriate size and length are determined by grading the stenotic lesion at the time of placement; usually, the stent is selected to be 1 mm larger than the size of the graft or the vessel to be treated and the length 5 mm longer than the stenotic lesion on each side. The stent comes already mounted in a device that is inserted through the sheath located at the arterial limb of the graft. A roadmap, contrast injection, of the stenotic lesion is performed. The stent is placed at the site of the stenotic lesion and deployed under fluoroscopic guidance ( Fig. 28-6 ). A final angiogram is performed to assess for patency and proper placement of the stent.

FIGURE 28-6 A, Angiogram demonstrates a severe stenotic lesion at the level of the venous anastomosis and the draining vein of a left forearm AV graft. The stenotic lesion has been graded before stent deployment. B, Spot film shows the stent fully deployed. C, DSA of the left forearm AV graft shows excellent results after stent deployment.

Complications of stent deployment include those related to angioplasty. In addition, underestimation of the required stent size may result in stent migration to the systemic circulation. If the stent is placed at a site at which another vessel joins the main venous outlet, that vessel may be completely or partially occluded. Finally, a potential long-term complication is intrastent restenosis or thrombosis, which will require multiple frequent reinterventions.

PROCEDURES INVOLVING ARTERIOVENOUS FISTULAS

Preoperative Vascular Mapping

The need to increase placement of native AV fistulas has been highlighted by the K/DOQI guidelines^[1] and by the Fistula First initiative (www.fistulafirst.org). There is widespread consensus among nephrologists and surgeons about the importance of maximizing fistula prevalence among hemodialysis patients. Achieving this goal, however, requires overcoming a number of hurdles, including timely referral of the patient with chronic kidney disease to the nephrologist and access surgeon, timely placement of an AV fistula, adequate maturation of new fistulas, and successful cannulation of the fistula for dialysis.^[8] In the past, the surgeon's decision about the type and location of vascular access placed was determined by a physical examination of the extremity, with and without a tourniquet. This approach had the potential for substantial errors. The surgeon may not be able to adequately visualize the veins in obese patients. As a result, the surgeon might place an AV graft when a fistula could have been feasible. In other patients, the surgeon may decide to place a radiocephalic fistula after visualizing a large diameter cephalic vein at the wrist. However, an unsuspected stenosis or thrombosis in a proximal portion of that vein would doom the success of this fistula.

The use of preoperative sonographic vascular mapping has been shown to substantially increase the proportion of patients receiving a fistula rather than a graft. A prospective pilot study at UAB compared the surgeon's decision about access placement in 70 consecutive chronic kidney disease patients, before and after the results of preoperative vascular mapping were provided to the surgeon.^[69] In almost one third of the patients, the surgeon changed her or his mind about the intended access procedure after receiving the mapping results. In most of these cases, the surgeon decided to place a fistula rather than a graft, or changed her or his mind about the location of the fistula.^[69] On the basis of these promising results, a program of routine preoperative vascular mapping was implemented. The results were dramatic: compared with the historical control period, the proportion of patients having a fistula placed increased from 34% to 64%. Moreover, the proportion of patients dialyzing with an AV fistula doubled from 16% to 34%.^[70] Similar increases in fistula placement and fistula placement after introduction of preoperative vascular mapping have been documented by other investigators ( Table 28-9 ), although a reduction in primary fistula failure has not been a consistent finding in all studies. ^{[70] [71] [72] [73]}

TABLE 28-9 -- Effect of Preoperative Vascular Mapping on Vascular Access Outcomes

Reference	Fistulas Placed (%)		Primary Fistula Failure (%)		Prevalence of Fistula Use (%)
	Pre-VM	Post-VM	Pre-VM	Post-VM	Pre-VM	Post-VM
Silva et al, 1998[73]	14	63	36	8	8	64
Ascher et al, 2000[71]	0	100	N/A	18	5	68
Gibson et al, 2001[72]	11	95	18	25	N/A	N/A
Allon et al, 2001[70]	34	64	54	46	16	34
Sedlacek et al, 2001[182]	N/A	62	N/A	25	N/A	N/A
Mihmanli et al, 2001[183]			25	6
Miller et al, 1997[184]	N/A	76

Reproduced from Allon M, Robbin ML: Increasing arteriovenous fistulas in hemodialysis patients: Problems and solutions. Kidney Int 62:1109–1124, 2002.

N/A, not available; VM, preoperative vascular mapping.

Although most centers have utilized sonographic vascular mapping, some have used venograms.^[74] In patients with stage 4 chronic kidney disease who have not yet started dialysis, there is a theoretical concern of contrast nephropathy precipitating the need for initiation of dialysis. However, in a series of 25 patients with a mean glomerular filtration rate of 13 mL/min, none developed acute renal failure after undergoing angiography with 10 to 20 mL of low-osmolality contrast material.^[75] Another potential risk is that venography of difficult-to-stick veins may injure veins required for future fistula creation. Venipuncture should be performed in the hand veins if at all possible, and the cephalic vein should be avoided at all costs.

Technical Procedure: Sonographic Preoperative Vascular Mapping

Vascular measurements are performed with the patient in a seated position, with the arm resting comfortably on a Mayo stand. All measurements are performed in the anteroposterior dimension in the transverse plane ( Fig. 28-7 ). The minimum vein diameter for a native arteriovenous fistula is 2.5 mm. The minimum vein diameter for graft placement is 4.0 mm. The minimum arterial diameter for either fistula or graft placement is 2.0 mm. Veins are assessed for stenosis, thrombus, and sclerosis (thickened walls).

FIGURE 28-7 A, Venous mapping: Venous ultrasound shows a transverse section of a cephalic vein being measured (0.36 cm). B, Venous mapping: Doppler flow measurements and color Doppler ultrasound shows a longitudinal section of a left forearm radial artery that is 1.3 cm deep and 1.5 mm in diameter.

First, the radial artery diameter at the wrist is measured. A tourniquet is then placed at the mid to upper forearm. The veins above the wrist are percussed for 2 minutes, with special emphasis on the cephalic vein area. Sequential measurements are made of the cephalic vein at the wrist and mid and cranial forearm. Any other dorsal or volar veins at the wrist are also measured and followed up the arm, according to established diameter criteria. The tourniquet is sequentially moved up the arm, and cephalic, basilic, and brachial vein diameters are measured.

After the tourniquet is removed, the subclavian and jugular veins are assessed for stenosis and thrombus. Evidence of a more central stenosis is determined by analysis of the spectral Doppler waveform for respiratory phasicity and transmitted cardiac pulsatility. If there is a clinical or sonographic suspicion of central vein stenosis, a venogram or magnetic resonance venography (MRV) is obtained.

Measurements are recorded on a worksheet. The sonographic measurements are used by the surgeon to select the most appropriate vascular access, on the basis of the following list agreed upon by our nephrologists, radiologists, and vascular surgeons, from most desirable to least desirable:

	1.	Nondominant forearm cephalic vein fistula.
	2.	Dominant forearm cephalic vein fistula.
	3.	Nondominant or dominant upper arm cephalic vein fistula.
	4.	Nondominant or dominant upper arm basilic vein transposition fistula.
	5.	Forearm loop graft.
	6.	Upper arm straight graft.
	7.	Upper arm loop graft (axillary artery to axillary vein).
	8.	Thigh graft.

Salvage of Immature Fistulas

Compared with AV grafts, fistulas require a much lower frequency of intervention (angioplasty or thrombectomy) to maintain their long-term patency for dialysis. However, fistulas have a substantially higher primary failure rate (fistulas that are never usable for dialysis). The proportion of fistulas with primary failure has ranged from 20% to 50% in multiple recent series, even when routine preoperative vascular mapping has been employed.^[8] Primary fistula failures fall into two major categories: early thrombosis and failure to mature. ^{[76] [77] [78]} Early thrombosis refers to fistulas that clot within 3 months of their creation, before they have been used for dialysis. Failure to mature refers to fistulas that never develop adequately to be cannulated reproducibly for dialysis.

Native fistulas are created by performing a direct anastomosis between a high-pressure artery and a low-pressure vein. Exposure of the vein to the high arterial pressure causes it to dilate and increase its blood flow. To be used reproducibly for dialysis, a fistula must have a large enough diameter to be safely cannulated with large-bore dialysis needles, and a sufficiently high access blood flow to permit a dialysis blood flow of 350 mL/min or higher. It also must be superficial enough for the landmarks to be easily appreciated by the dialysis staff performing the cannulation. The increases in blood flow and draining vein diameter occur fairly rapidly after fistula creation. Whereas the blood flow in a normal radial artery is only 20 to 40 mL/min, it increases more than 10-fold within a few weeks of fistula creation. In one study, the mean access blood flow in successful fistulas was 634 mL/min 2 weeks postoperatively^[79]; in a second study, it was 650 mL/min 12 weeks after fistula creation.^[80] Moreover, the mean access blood flows and fistula diameters are not significantly different in the 2nd, 3rd, and 4th months after fistula creation.^[81] This implies that determination of whether a new fistula is likely to be used successfully for dialysis should be possible within 4 to 6 weeks of the initial surgery.

In some patients, maturation of the fistula can be assessed easily by clinical evaluation by the nephrologist, surgeon, or an experienced dialysis nurse. In less straightforward cases, duplex ultrasound may be useful in predicting whether a new fistula can be used successfully for dialysis. One pilot study used a combination of two simple sonographic criteria to assess fistula maturation: fistula diameter and access blood flow.^[81] When the ultrasound documented a draining vein diameter 4 mm or more and an access blood flow of 500 mL/min or more, 95% of the fistulas were subsequently usable for dialysis. In contrast, when neither criterion was met, only 33% of the fistulas achieved adequacy for dialysis. The likelihood of fistula adequacy for dialysis was intermediate (∼70%) when only one of the two criteria was met.

Failure of a fistula to mature can be caused by one of several anatomic defects, which can be identified by either sonography or angiography.^[82] Stenosis at the anastomosis or in the draining vein is one such problem. Another possibility is that the draining vein has one or more large side branches. When this occurs, the arterial blood flow is distributed among two or more competing veins, thereby limiting the increase in blood flow in each. A third scenario may be observed in obese patients, in which the fistula has adequate caliber and blood flow but is simply too deep to be cannulated safely by the dialysis staff. In most patients, these anatomic lesions can be corrected by radiologic or surgical interventions. Stenotic lesions can be treated by angioplasty or surgical revision. Superficial side branches can be ligated by a suture through the skin; deeper branches can be embolized. Finally, the surgeon can superficialize fistulas that are too deep to be cannulated safely.

In immature fistulas with one or more of these anatomic lesions, specific interventions to correct the underlying lesion may promote subsequent fistula maturation. Several published series have evaluated the ability to salvage immature fistulas to ones that are subsequently usable for dialysis. A number of studies utilizing only radiographic procedures (angioplasty of stenotic lesions or obliteration of side branches) in immature fistulas have had a high success rate ( Table 28-10 ). ^{[74] [83] [84] [85] [86]} An initial salvage (ability to use the fistula for dialysis) was accomplished in 80% to 90% of patients, with a subsequent 1-year primary patency of 39% to 75%. In another study utilizing a combination of radiologic and surgical salvage procedures in an unselected dialysis population, the salvage rate was more modest at 44%.^[78] Of interest, the frequency of a salvage procedure for immature fistulas in that study was twice as high in women as in men.

TABLE 28-10 -- Effect of Salvage Procedures on Immature Fistulas

Reference	Pts (N)	Type of Intervention	Usable for Dialysis (%)	Primary Patency at 1 Yr (%)
Beathard et al, 1999[83]	63	PTA, vein ligation	82	75
Turmel-Rodrigues et al, 2001[85]	69	PTA, vein ligation	97	39
Miller et al, 2003[78]	41	PTA, vein ligation, surgical revision	44	N/A
Beathard et al, 2003[84]	100	PTA, vein ligation	92	68
Asif et al, 2005[74]	24	PTA, vein ligation	92	N/A
Nassar et al, 2006[86]	119	PTA, vein ligation	83	65

N/A, not available; PTA, percutaneous transluminal angioplasty.

Technical Procedure: Salvage of Immature Fistulas

Angioplasty of Stenotic Lesions

The stenosis at the juxta-arterial anastomosis can be treated with sequential balloon dilatations. This requires two to five treatments until the size of the anastomosis is appropriate. Long segments of stenotic lesions at the level of the most proximal part of the venous outlet near the anastomosis are amenable to balloon angioplasty and sometimes may require several follow-up interventions.

The AV fistula is initially accessed at its most proximal portion with a 21-gauge micropuncture needle. A cope-mandrel-wire is passed into the venous circulation, and then a 4-French catheter sheet is exchanged for the needle. Digital subtracted angiograms (DSAs) of the venous outlet and central circulation and a reflux retrograde arteriogram are performed. Once the lesion is identified, then the proper technique is selected.

If the lesion is at the juxta-arterial anastomosis, then a second access is achieved by inserting a micropuncture needle from the most distal portion of the fistula toward the AV anastomosis. The needle is exchanged for a 5-French catheter sheath and a wire (0.014–0.018 inch) is passed into the fistula and through the arterial anastomosis into the arterial circulation. An arteriogram of the AV anastomosis is performed, and the stenotic lesion is evaluated and graded. Depending on the severity of the stenosis, a balloon is selected from sizes between 2 and 6 mm in diameter and from 10 to 40 mm in length. The balloon is introduced into the stenotic lesion and inflated carefully up to its nominal pressure. Subsequent angiograms are performed for a postangioplasty grading of the lesion ( Fig. 28-8 ). Intrafistula and systemic pressures are taken before and after the angioplasty and the corresponding ratios calculated. Patients are brought back to the intervention suite 2 to 4 weeks later for a second-look angiogram of the fistula.

FIGURE 28-8 A, Fistula salvage: DSA of a radiocephalic AV fistula shows a severe stenotic lesion at the level of the juxta-arterial anastomosis. B, Fistula salvage: Postangioplasty DSA of a radiocephalic fistula shows radiologic improvement of the stenotic lesion at the level of the juxta-arterial anastomosis.

If the lesion is located in the proximal part of the fistula or at the central vessels, then the initial venous access is appropriate. The initial 4-French catheter is exchanged for a 4- to 6-French sheath and a glidewire passed into the central venous circulation. The balloon is selected depending on the severity of the lesion and also its location. Sizes can range from 4 to 8 mm in the peripheral venous circulation and up to 14 mm in the central circulation. Once the angioplasty is done, DSAs are performed for postangioplasty grading of the lesion. Intrafistula and systemic pressures are measured. Patients are followed at their local dialysis center and if the fistula does not mature or the nursing personnel are still having problems cannulating the fistula, then a second-look angiogram of the fistula is indicated.

Ligation of Accessory Veins

Accessory veins can be treated either by surgical ligation or by endovascular coil deployment. Treatment of these lesions requires a well-trained interventionist owing to the difficult technical approach to these lesions. Accessory veins are treated depending on size, location, and number ( Fig. 28-9 ). Some interventionists advocate percutaneous ligation of superficial accessory veins at time of the initial angiogram of the fistula.^[87] If the accessory vein is deep and has a good lumen size, then surgical ligation is indicated. If the accessory vein is deep but has a small lumen size, then a coil deployment should be considered.

FIGURE 28-9 DSA of a left radiocephalic AV fistula showing multiple collaterals. There is a metallic plate from a prior open reduction and internal fixation of a radius bone fracture.

The fistula is accessed and, depending on its size, an appropriate sheath is introduced. A selective catheter is introduced in each accessory vein, and an appropriate size coil is deployed. A final angiogram of the fistula is taken to ascertain proper coil deployment and occlusion of all collateral veins.

Angioplasty of Fistulas

Although the frequency of interventions is severalfold lower in fistulas than in grafts,^[8] fistulas are also susceptible to developing stenosis and thrombosis. Most studies have documented a comparable primary patency of fistulas and grafts after elective angioplasty ( Table 28-11 ), although one study observed a higher primary patency in fistulas.^[88] As is the case with angioplasty of grafts, the primary patency of fistulas after angioplasty is inversely related to both the magnitude of postangioplasty stenosis and the magnitude of the postangioplasty intra-access-to-systemic pressure ratio.^[25] Patient age, race, diabetic status, presence of peripheral vascular disease, access location, and number of stenotic sites have not been associated with the likelihood of vascular access patency after angioplasty.^[25]

TABLE 28-11 -- Primary Patency After Elective Angioplasty: Fistulas Versus Grafts

Reference	Primary Access Patency at 6 Mo
	Grafts (%)	Fistulas (%)
Safa et al, 1996[28]	43	47
Turmel-Rodrigues et al, 2000[92]	53	67
McCarley et al, 2001[42]	37	34
Van der Linden et al, 2002[88]	25	50
Maya et al, 2004[25]	52	55

Technical Procedure: Angioplasty of Fistulas

The fistula is accessed at its most proximal portion with a 21-gauge micropuncture needle. A cope-mandrel-wire is passed into the venous circulation. The needle is exchanged for a 4-French catheter. Initial DSA of the fistula is performed, including the venous outlet and central circulation. Lesions with more than 50% stenosis are considered to be hemodynamically significant and undergo angioplasty. Once the stenotic lesion has been identified and graded, then a glidewire is introduced to the central circulation and the catheter exchanged for a 6-French catheter sheath. An angioplasty balloon is introduced through the catheter sheath. Balloon sizes vary depending on the vessel to be treated. The balloon is placed at the level of the stenotic lesion and inflated to its nominal pressure for 30 to 90 seconds. High pressures (>20 atm) are frequently needed in fistulas.^[57] A final DSA is performed to assess for residual stenosis and further treatment of the stenotic lesion ( Fig. 28-10 ). The patient's intrafistula pressure and systemic pressure are measured before and immediately after the intervention, and a reduction intrafistula-to-systemic pressure ratio is used to confirm hemodynamic improvement.

FIGURE 28-10 A, DSA of a left radiocephalic AV fistula shows a longs severe segment of stenosis distal to the arterial anastomosis followed by a pseudoaneurysm of the fistula. B, Spot film of a left radiocephalic AV fistula shows the segment of stenosis being angioplastied. C, Postangioplasty DSA shows a successful treatment; the pseudoaneurysm is unchanged.

The major complications of this procedure are vessel extravasations and rupture of the vessel after the angioplasty ( Fig. 28-11 ). Deploying a covered stent can treat these complications. Surgical repair is indicated if the rupture is not corrected by stent placement.

FIGURE 28-11 A, Angioplasty complication: DSA shows a rupture of the left cephalic vein after aggressive percutaneous transluminal angioplasty. There is a coexisting stenosis of the left subclavian. B, Angioplasty complication: DSA shows salvage and correction of the complication by deploying a covered stent.

Percutaneous Mechanical Thrombectomy and Thrombolysis of Arteriovenous Fistulas

Dealing with thrombosed fistulas is one of the most challenging aspects in interventional nephrology.^[89] Thrombectomy of aneurysmally dilated fistulas is the most difficult technically. The most common cause of fistula thrombosis is an underlying stenotic lesion in the venous outflow circulation (either peripherally or centrally). Less common causes include needle infiltration,^[90] excessive manual pressure for hemostasis at the needle insertion site, or severe and prolonged hypotension. Successful restoration of patency in a thrombosed fistula requires expeditious thrombectomy. Several series have reported on the outcomes of radiologic thrombectomy of fistulas. ^{[89] [91] [92] [93] [94] [95] [96] [97]} The immediate technical success has been fairly high, ranging from 73% to 93%. The primary patency of these fistulas after thrombectomy has ranged from 27% to 81% at 6 months and 18% to 70% at 1 year ( Table 28-12 ). In one study, the primary patency after thrombectomy was lower in upper arm fistulas than in those in the forearm.^[92] However, with additional interventions, the secondary patency of these fistulas has been 44% to 93% at 1 year. Considering that the alternative would be to abandon the thrombosed fistula and proceed with placement of a new fistula, concerted efforts to salvage thrombosed fistulas are extremely worthwhile.

TABLE 28-12 -- Primary Fistula Patency After Thrombectomy^[*]

Reference	Procedures (N)	Primary Patency At
		6 Mo (%)	12 Mo (%)
Haage et al, 2000[91]	54	N/A	27
Turmel-Rodrigues et al, 2000[92]	54 FA	74	47
	9 UA	27	27
Rajan et al, 2002[96]	30	28	24
Liang et al, 2002[95]	42	81	70
Shatsky et al, 2005[97]	44	38	18

FA, forearm; N/A, not available; UA, upper arm.

*	Series with fewer than 25 procedures not included.

Technical Procedure: Percutaneous Thrombectomy of Fistulas

Although more challenging than graft thrombectomy, AV fistulas can be declotted successfully. There are few contraindications, including concurrent infection, fistula immaturity, and very large aneurysms. The technical challenges include difficulty in the initial cannulation of a thrombosed fistula, complete removal of large thrombi, and successful treatment of recalcitrant stenotic lesions.

The fistula is accessed at its most distal portion toward the arterial anastomosis with an 18-gauge needle, either blind or by guided ultrasonography. A glidewire is introduced and a catheter placed over the glidewire. A thrombolytic agent, 2 to 4 mg of Alteplase (t-PA), is infused and left in the fistula for 1 hour. The patient is taken back to the intervention suite, the glidewire is repositioned, and the catheter is replaced with a conventional 6-French sheath. A percutaneous thrombectomy over-the-wire device can be used, but the wire must be advanced into the arterial circulation. After a successful thrombolysis of the fistula, a Fogarty balloon is passed beyond the arterial anastomosis and pulled back to dislodge the plugging clot. Once the thrombus is cleared and blood flow reestablished, a DSA of the fistula is taken to evaluate for stenotic lesions along the venous outlet track or central circulation. If a lesion is encountered in the upstream or central circulation, then a second access is placed and the lesion angioplastied.

Manual aspiration without the use of thrombolytic agents is another approach. A sheath is placed to gain access to the venous outflow. A guide catheter with a large lumen is introduced through the sheath. The aspiration is performed with a 50-mL syringe connected to the guide catheter, while the catheter is removed with back-and-forth movements. The contents of the syringe are flushed, and the aspiration maneuver is repeated several times to remove all the thrombus. A second sheath is introduced toward the arterial anastomosis, and the same aspiration technique is performed to aspirate the rest of the thrombus located between the introducer and the anastomosis. A Fogarty balloon is passed beyond the arterial anastomosis and pulled back to dislodge the arterial plug clot. Digitally subtracted anterograde angiograms of the fistula are performed to assess for patency and look for stenotic lesions. Angioplasty of any hemodynamically stenotic lesion in the vascular access circuit is performed. A final DSA of the fistula is performed, and the patient's intra-access pressure and systemic pressure are measured before and immediately after the intervention. The pressure ratio is calculated to confirm improvement in blood flow.

The major complications of this procedure are vessel extravasations and rupture of the vessel after the angioplasty. Pulmonary embolism is of greater concern with fistula Thrombectomy than with graft thrombectomy, owing to the larger volume of thrombus. Finally, arterial emboli distal to the AV anastomosis may occur with greater frequency than for grafts.

NOVEL TECHNIQUES FOR TREATMENT OF SEVERE STENOTIC LESIONS

Cutting Balloon

Despite the use of angioplasty with high-pressure balloons and prolonged inflations, some lesions remain severely stenotic. The use of cutting balloons has been advocated as a tool to treat these lesions by creating a controlled rupture of the vessel wall. The cutting balloon catheter is a balloon with four blades arranged along the balloon. When the balloon is inflated, it exposes the blades to the offending lesion, creating a controlled rupture of the intima or hyperplastic fibrous tissue. A regular angioplasty balloon can be used afterward to shape the vessel and expand it to the desired diameter. It has been used in lesions at all levels from intragraft to central lesions. Preliminary reports suggested that cutting balloons may result in superior outcomes than those obtained with conventional angioplasty. ^{[98] [99]} In one series of nine patients, grafts with high-grade venous anastomosis stenosis were treated with cutting balloon plus stent deployment.^[98] The patients were followed up to 20 months with a functional graft. However, a randomized, multicenter clinical trial comparing use of the cutting balloon with conventional angioplasty for treatment of graft stenosis observed no advantage to the cutting balloon. The primary patency at 6 months was 48% in grafts treated with a cutting balloon versus 40% for grafts treated with angioplasty. Device-related complications occurred in 5% of the patients in the cutting balloon group (primarily vein rupture or dissection) compared with none of the patients whose grafts were treated with angioplasty alone.^[100] The considerable additional cost of cutting balloons is substantial and precludes it ever being used routinely.

Cryoplasty Balloon

Cryotherapy with the cryoballoon is a novel therapy for patients with intractable stenoses at the venous anastomosis of AV grafts. This technique utilizes cold temperatures at the balloon site to cause apoptosis of the intima layer. Rifkin and co-workers^[101] reported the outcomes of five patients with recurrent stenotic lesions at the venous anastomosis that were treated with the cryoballoon. The primary patency increased from 3 weeks after angioplasty alone to more than 16 weeks after cryoplasty. There are no published randomized studies comparing the outcomes of graft stenosis treated with cryoplasty versus with angioplasty alone.

CENTRAL VEIN STENOSIS

Central vein stenosis is a frequent occurrence in hemodialysis patients.^[11] Acute or chronic trauma of the central vessels by either temporary or permanent dialysis catheters is the major cause.^[102] Stenosis leads to impairment of venous return on the ipsilateral extremity and might, in turn, result in malfunction or thrombosis of the vascular access. Although it may be asymptomatic, patients with central vein stenosis most commonly present with ipsilateral upper extremity edema. In some patients, a previously unappreciated central vein stenosis becomes evident clinically after creation of an ipsilateral fistula or graft. The diagnosis can be confirmed by angiography, ultrasound, or MRV.

The most commonly encountered location of central vein stenosis is at the junction of the cephalic vein with the subclavian vein (not catheter injury related). Other central veins that may be affected include the subclavian vein, brachiocephalic vein, and superior vena cava ( Fig. 28-12 ). In patients with tunneled femoral catheters, central vein stenosis may occur in the external iliac vein, common iliac vein, or inferior vena cava, resulting in ipsilateral lower extremity edema. The stenotic lesion is an aggressive myointimal proliferation or clot and fibrin sheath formation around indwelling dialysis catheters that is organized and incorporated into the vessel wall. These may progress over time to complete occlusion of the venous circulation. If left untreated, central vein stenosis may cause increased retrograde pressure and formation of venous collaterals. In some patients, the collaterals are sufficiently well developed to permit adequate venous drainage that prevents formation of edema.

FIGURE 28-12 DSA shows a severe stenosis of the left innominate vein. There are multiple ipsolateral and across-the-neck collaterals draining into a normal right innominate vein.

The treatment of choice of central vein stenosis is percutaneous transluminal angioplasty (PTA) of the stenotic lesion. ^{[44] [103] [104] [105] [106] [107] [108] [109]} Unfortunately, the long-term success is quite poor owing to a combination of elastic recoil and aggressive myointimal hyperplasia. In one study, the primary patency was substantially shorter after angioplasty of central vein stenosis compared with stenoses at more peripheral locations.^[26] As a result, patients with central vein stenosis require frequent angioplasties to treat recurrent lesions.

Stent placement has been attempted in the management of refractory central vein stenosis owing to elastic recoil ( Fig. 28-13 ). Several small series have reported the outcomes of stent placement for refractory central venous stenotic lesions. These studies have been limited by their retrospective study design, the small numbers of patients, and the absence of a control group. In two uncontrolled series, the primary patency after stent deployment for central vein stenosis was 42% to 50% at 6 months and only 14% to 17% at 1 year. ^{[44] [103]} Although there are no published randomized studies comparing stent deployment with angioplasty of central vein stenosis, the primary patency in series utilizing stents has been no better than that achieved with angioplasty alone. In patients with ipsilateral vascular access and persistent upper extremity edema despite attempted angioplasty, the only recourse may be ligation of the vascular access.

FIGURE 28-13 A, DSA shows a severe stenotic lesion of the left subclavian. There is also a stent at the left cephalic vein. B, DSA shows a stent deployed at the severe stenotic lesion of the left subclavian with excellent initial results. C, DSA taken 12 months after the initial placement of a stent at the left subclavian shows intrastent stenosis due to significant myointimal hyperplasia.

INDWELLING HEMODIALYSIS CATHETERS

Nontunneled Temporary Hemodialysis Catheters

Temporary hemodialysis catheters are indicated for acute dialysis treatments. They are made of polyurethane, polyethylene, or polytetrafluoroethylene; they have a double lumen and are semirigid and easy to place in the internal jugular (preferably on the right side), femoral, and rarely, subclavian veins. Each site has its advantages and disadvantages, but if the catheters are placed in the femoral vein, the catheter should not stay longer than 72 hours, and the internal jugular vein catheters not longer than 1 week, owing to the high risk of bacteremia with longer dwell times.^[110] The subclavian vein is usually used only if there is no other access available because there is an increased risk for stenosis and occlusion of the central vessels.^[102] If the upper vessels are used, the catheter should be long enough to have its tip at the junction of the right atrium and superior vena cava. If the femoral vein is used, the catheter's tip should be located in the inferior vena cava. If the patient is expected to remain catheter-dependent for a longer time period, a tunneled catheter should be placed. Temporary hemodialysis catheters can be placed blindly, by ultrasound or fluoroscopic guidance. A chest radiograph should always be obtained after placement of a central vein dialysis catheter in the chest; it is not needed after placement of a femoral dialysis catheter.

Technical Procedure: Insertion of Temporary Dialysis Catheters

The procedure is usually performed at patient's bedside, but occasionally, it is performed in the interventional suite. Strict sterile technique and use of local anesthesia are indicated. Access to the femoral or internal jugular vein may be done either blindly or by real-time ultrasound guidance. Real-time ultrasound is highly recommended, as it decreases the number of attempts at vein cannulation and minimizes the risk of inadvertent arterial cannulation. An 18-guage needle is used for access. Once the vein has been cannulated, a J-wire is introduced through the needle and advanced into the venous circulation. The needle is exchanged for a series of dilators, and then a temporary dialysis catheter (19–24 cm in length) is introduced and sutured in place. The lumens are flushed and filled with heparin.

Potential complications at time of placement at the upper vessels include pneumothorax, vein or arterial perforation; mediastinal or pericardial perforation with possibility of hemothorax and cardiac tamponade; air embolism; and local hematoma with possible extension into the soft subcutaneous tissue of the neck and possible external obstruction of the airways. The long-term complications include development of stenotic lesions along the trajectory of the catheter, which may preclude the use of the ipsilateral limb for future creation of a vascular access. If the patient already has a documented stenotic lesion of the central vessels, placement of an indwelling catheter may cause life-threatening acute central vessel occlusion. Exit site infections and catheter-related bacteremia (CRB) are frequent complications of temporary dialysis catheters. Development of CRB requires institution of systemic antibiotics and removal of the nontunneled dialysis catheter.

The complications at the femoral site are less dramatic, but vein or arterial perforation and formation of AV fistula are possible. Deep vein thrombosis, local hematomas, exit site infections, and bacteremia are not uncommon complications. There is also a possibility of causing stenosis of the femoral, iliac, or inferior vena cava.

Tunneled Hemodialysis Catheters

Tunneled hemodialysis catheters are used for temporary vascular access in patients waiting for a maturation of a permanent vascular AV fistula or graft. They are also required for long-term access in patients who have exhausted all options for placement of a permanent access in all four extremities. Tunneled dialysis catheters are usually placed in a central vein in the chest, most commonly in the internal jugular vein and, rarely, in the subclavian vein. They have the same characteristics as temporary catheters but are longer and have a Dacron cuff, which is tunneled in the subcutaneous tissue. An inflammatory response around the cuff results in scar tissue, creating a mechanical barrier that prevents introduction of infection from the exit site into the bloodstream. As a result, the frequency of CRB is lower with tunneled dialysis catheters than with acute catheters. ^{[111] [112]}

Technical Procedure: Insertion of Tunneled Hemodialysis Catheters

Strict sterile technique, topical local anesthesia (1% lidocaine [Xylocaine]), and conscious sedation are used. Access to the internal jugular vein is guided by real-time ultrasound. A 21-guage micropuncture needle is used for access. Once the vein has been cannulated, a 0.018-inch guidewire is introduced through the needle and advanced under fluoroscopic guidance. The needle is removed and exchanged for a 4-French catheter. The guidewire and inner dilator are removed and a stiff 0.035-inch wire is passed through the catheter down into the inferior vena cava under fluoroscopic guidance. A skin pocket of about 1 cm is created at this location. The permanent indwelling hemodialysis catheter is attached to a tunneler device, and a tunnel is created lateral, down, and approximately 5 to 7 cm from the initial needle insertion. The catheter is buried under the skin. At this point, the tunneler device is discarded and a series of dilators are passed over the wire under fluoroscopic guidance, leaving a peel-away catheter sheath and inner dilator in place. The inner dilator and wire are removed, leaving the peel-away sheath behind. The tip of the catheter is introduced into the opening of the sheath and fed up to the junction of the superior vena cava and right atrium. The peel-away sheath is then removed. A final x-ray is taken to assess for kinks of the catheter and for placement ( Fig. 28-14 ). Sutures are placed at the initial skin incision and also at the entry site of the catheter. The catheter lumens are filled with heparin. The catheters are 14.5 or 15 French with lengths from 24 cm for right internal jugular, 28 cm for left internal jugular, and from 36 to 42 cm for femoral veins.

FIGURE 28-14 Spot film of an appropriate placement of a right internal jugular vein tunneled chronic dialysis catheter.

Complications at the time of placement are similar to those associated with temporary catheters. Internal jugular thrombosis develops in about 25% of tunneled catheters but is usually asymptomatic.^[113] Other long-term complications include dysfunction due to intraluminal thrombosis or fibrin sheaths, exit site infections, tunnel infections, and CRB.^[11]

Less Common Locations for Tunneled Hemodialysis Catheters

If prolonged use of upper extremity dialysis catheters leads to bilateral central vein occlusion, it becomes necessary to place a tunneled catheter in the femoral vein. ^{[114] [115]} The procedure for placement of a tunneled femoral catheter is similar to that for a tunneled internal jugular vein catheter, except that a longer (36–42 cm) catheter is required, and the catheter tip is placed in either the proximal inferior vena cava or in the right atrium ( Fig. 28-15 ).^[114] The subcutaneous tunnel is created in the anterior upper thigh. The primary patency of tunneled femoral catheters is significantly worse than that of tunneled internal jugular catheters.^[114] Presumably, some failures are due to kinking of the catheter in the groin when the thigh is flexed. However, the frequency of CRB is similar for patients with femoral and internal jugular dialysis catheters. The likelihood of CRB is proportional to the duration of catheter use.^[116] There is high (∼25%) frequency of symptomatic ipsilateral deep vein thrombosis after placement of a tunneled femoral catheter.^[114] Fortunately, this complication can be treated with long-term anticoagulation; thereby permitting continued use of the catheter. In patients on hemodialysis in whom the central veins in the chest and groin have been exhausted, the placement of tunneled dialysis catheters at unconventional sites (translumbar and transhepatic) has been described. Catheters at these locations should be considered as last-resort options, as they are associated with a substantial risk for complications.

FIGURE 28-15 A and B, Spot films of an appropriate placement of a left femoral vein tunneled chronic dialysis catheter.

For translumbar catheters, the insertion site is located at the level of vertebra L3, the needle is directed toward the inferior vena cava under fluoroscopic guidance; once venous access is achieved, a glidewire is placed. A tunnel is created from initial needle insertion at the lower back and around the waist of the patient with the entry site located at lower part of the abdominal flank. The permanent hemodialysis catheter is advanced through the tunnel and the cuff is buried in the adjacent subcutaneous tissue ( Fig. 28-16 ). ^{[117] [118]} The risk of bleeding and retroperitoneal hematoma is considerably higher than that associated with tunneled femoral vein catheters. The most common complication of translumbar catheters in one series of 10 patients is partial dislodgment of the catheters.^[118]

FIGURE 28-16 Spot film of an appropriate placement of a translumbar tunneled chronic dialysis catheter.

Interventional radiologists at some centers have placed transhepatic catheters. The right upper quadrant is prepped and draped in the usual manner. A 21-gauge needle is placed halfway through the liver in a direction parallel to the right of the middle hepatic veins under fluoroscopic guidance. Contrast material is injected through the needle, and the needle is withdrawn until a hepatic vein is visualized. Once a suitable vein is accessed, a glidewire is placed and advanced to the right atrium. A subcutaneous tunnel is created inferiorly to the insertion site, and a dual-lumen, cuffed hemodialysis catheter is placed. ^{[119] [120] [121]} The major complications are bleeding and perihepatic hematoma. Stavropoulos and associates^[120] reported a series of 36 transhepatic dialysis catheters placed in 12 patients. The mean survival of these catheters was only 24 days. The thrombosis rate was 2.40 per 100 catheter-days. The poor catheter patency rates were due to a high rate of late thrombosis.

Exchange of Tunneled Hemodialysis Catheters

There are two major indications for catheter exchange: dysfunction and infection. Catheter dysfunction is diagnosed when blood cannot be aspirated from the catheter lumen at the time of dialysis initiation, or more commonly, if it is not possible to consistently achieve a dialysis blood flow greater than 250 mL/min. In catheters that were previously delivering an adequate blood flow; intraluminal thrombus is the most common etiology for dysfunction, although a fibrin sheath may be the culprit in some patients. This problem is usually treated empirically in the dialysis unit by instilling t-PA into the catheter lumens.^[122] t-PA instillation is successful in about 70% to 80% of catheters, but problems with poor flow frequently recur within 2 to 3 weeks. If the thrombolytic agent does not improve the catheter flow, the patient is referred for catheter exchange.

An exit site infection usually resolves with topical antimicrobial agents or oral antibiotics and is not usually an indication for catheter removal. However, if the patient has a tunnel track infection, catheter removal is mandatory. Finally, CRB is a common indication for catheter replacement.^[10] In one series, the cumulative risk of CRB among catheter-dependent patients was 35% at 3 months and 48% at 6 months.^[116] CRB is suspected when a catheter-dependent patient experiences fever or chills, and it is confirmed by blood cultures from the catheter and a peripheral vein growing the same organism.^[10] When a single set of blood cultures is positive, CRB is still the most likely diagnosis in the absence of clinical evidence of an alternative source of infection.

The clinical management of CRB has evolved in the past few years ( Table 28-13 ).^[10] In the subset of patient whose fever persists after 48 to 72 hours of appropriate systemic antibiotics (∼10%–15% of patients with CRB), removal of the infected catheter is mandatory. For the remaining patients, several management options are available. The first option is to continue systemic antibiotics without removal of the infected catheter. Unfortunately, the infection is infrequently eradicated with this approach; once the course of systemic antibiotics has been completed, bacteremia recurs in 63% to 78% of patients. ^{[123] [124] [125] [126] [127]} Moreover, delays in removing an infected catheter may result in metastasic infection, such as endocarditis, septic arthritis, or epidural abscess.^[128] Prompt removal of the catheter removes the source of infection. However, in order to continue delivering dialysis to the patient, it is necessary to place a temporary (nontunneled) dialysis catheter. Once the bacteremia has resolved, a new tunneled catheter is placed. In an effort to reduce the number of required access procedures, a number of investigators have evaluated the strategy of exchanging the infected catheter for a new one over a guidewire. Several publications have documented the safety and efficacy of this approach. ^{[126] [129] [130] [131] [132]}

TABLE 28-13 -- Management Strategies for Catheter-Related Bacteremia

Systemic antibiotics alone

Catheter removal with delayed placement of a new, tunneled catheter

Catheter exchange over a guidewire

Antibiotic lock

In the past few years, there has been a growing recogni-tion of the central role of bacterial biofilms in causing CRB. Biofilms develop on the inner surface of the lumens of central vein catheters in as little as 24 hours and are relatively refractory to conventional plasma concentrations of antibiotics. ^{[133] [134] [135]} Instillation of a concentrated antibiotic solution into the catheter lumen after each dialysis session (“antibiotic lock”) can frequently kill the bacteria in the biofilm. This approach can potentially remove the source of the infection (the biofilm) while permitting catheter salvage. The use of antibiotic locks, in conjunction with systemic antibiotics, has been shown to eradicate the infection, while salvaging the catheter, in about two thirds of the patients. ^{[10] [136] [137] [138] [139]} This strategy is not associated with an increased risk of metastasic infections compared with prompt catheter removal or exchange of the infected catheter over a guidewire. At the authors' institution, implementation of an antibiotic lock protocol has dramatically reduced the frequency of catheter exchanges owing to infection.

Technical Procedure: Exchange of Tunneled Hemodialysis Catheters

Patients are brought to the interventional suite for exchange of permanent indwelling hemodialysis catheters. Strict sterile technique, topical local anesthesia (1% lidocaine), and conscious sedation are provided. Under fluoroscopic guidance, an extra-stiff 0.035-inch wire is passed through one of the lumens of the catheter and advanced to the inferior vena cava. The catheter cuff located near the exit site in the subcutaneous tissue is dissected, and the catheter is pulled out, leaving the wire behind. The exit site and the wire are cleaned and wiped with antibacterial soap. The operators' gloves are exchanged. A new permanent hemodialysis catheter is then prepped and advanced over the wire into place. The tip of the catheter is advanced to the inferior vena cava for the femoral vein or to the junction of the superior vena cava and right atrium for the internal jugular vein. Finally, the wire is removed, and the catheter is sutured in place. The lumens of the catheter are filled with heparin.

Subcutaneous Hemodialysis Ports

Implantable subcutaneous vascular access devices (e.g., LifeSite) have been available commercially for several years.^[140] There is no clear indication for their use, except as a bridge device while waiting for maturation of a fistula. Theoretically, the risk of CRB should be lower with subcutaneous dialysis devices, as there is no portion protruding through the skin. However, a randomized clinical trial comparing a subcutaneous dialysis device with conventional tunneled dialysis catheters found no difference in the frequency of bacteremia, unless isopropyl alcohol was instilled into the subcutaneous device after each dialysis session.^[141] Although these devices are no longer commercially available, some dialysis patients still have them in place.

Technical Procedure: Implantation of Subcutaneous Dialysis Ports

This access device has two titanium valves that are connected to two silicone catheters, which are placed individually into the central venous circulation with the same technique as the one described for tunneled catheters. The tip of one of the catheters is placed in the right atrium and the other tip in the superior vena cava. The most common placement site is the internal jugular vein, but external jugular and femoral veins can also be used. If the femoral vein is used, the tips of both catheters should be in the inferior vena cava, about 2 to 3 cm apart. Two different subcutaneous tissue pockets are created next to the tunneled catheters, and the titanium valve devices are implanted and connected to the catheters. The pockets are created in an area of easy access for cannulation by the dialysis nursing personnel. It is important to avoid creating the pockets in areas that will cause discomfort to the patient (i.e., above the clavicle or above the inguinal area). The device should not be deeper than 10 to 15 mm below the skin for easy access but not less than 10 mm because skin erosion and necrosis can occur. The medial titanium valve device is used for blood drawing, and the lateral is used for blood return during dialysis. To access the system and establish high blood flow rates, a standard 14-gauge needle is inserted through the skin into the device, and the needle opens the internal valve, allowing blood to flow.

Complications at time of placement are similar to those for tunneled catheters because the insertion technique of the indwelling catheters is similar. In addition, there is a risk for bleeding and hematoma formation at the site of the created subcutaneous tissue pocket. Late complications include malfunction of the valve devices, clotting and infection of the catheter lines, infection of the subcutaneous tissue pockets, and erosion and necrosis of the skin overlying the devices.

PERITONEAL DIALYSIS CATHETER PROCEDURES

Peritoneal dialysis (PD) is an alternative to hemodialysis in patients with end-stage renal disease. Although it is widely used in many countries, less than 10% of the U.S. dialysis population is treated by this modality.^[142] PD catheters can be placed into the abdominal cavity by surgeons, ^{[143] [144] [145]} interventional radiologists,^[146] or interventional nephrologists.^[147] There are several techniques: blind (Seldinger) technique,^[148] surgical placement,^[143] peritoneoscopic,^[149] laparoscopic,^[150] Moncrief-Popovich technique,^[151] and fluoroscopic insertion.^[147] Incorporation of PD catheter placement in an established interventional nephrology program increases the utilization of this dialysis modality.^[152]

Peritoneal catheters are made of either silicone rubber or polyurethane. The Tenckhoff catheter is still the most common type of PD catheter placed. The intraperitoneal portion of the catheter can be either straight, coiled, Ash (T-Flutted), or fitted with a silicone disk.^[153] The extraperitoneal portion of the catheter may be straight or have a swan-neck design with single- or double inner cuffs, or a combination of a single cuff and a silicone disk. The most widely used PD catheter is the double-cuff, swan-neck, coiled Tenckhoff design. This design has been shown to decrease mechanical complications (i.e. inflow and outflow problems). It also decreases pain during infusion and has fewer propensities for migration. The swan-neck design was introduced to avoid cuff extrusions.^[154] The intraperitoneal portion of the catheter should be placed between the visceral and the parietal peritoneum near the pouch of Douglas. The inner cuff should be inserted in the abdominal wall musculature (rectus muscle) to prevent leaks. The outer cuff should be located in the subcutaneous tissue to create a dead space between the two cuffs, which is believed to prevent migration of infections coming from the exit site. The subcutaneous tract and exit site should face downward and laterally to avoid exit site infection. The exit site should be determined and marked prior to the insertion while the patient is in the upright position. The belt-line, prior surgical sites, and the abdominal midline should be avoided. Postoperative catheter care is very important. The catheter should be covered with a nonocclusive dressing and should not to be used for 10 to 14 days. The catheter should be flushed at least two or three times per week with saline or dialysate solution until the patient is ready to start PD.^[155] Usually, PD is started 2 to 3 weeks after placement of the catheter to allow for wound healing and avoid leaks. Low-volume PD may be attempted within 24 hours of catheter placement, if no other dialysis access is available.^[156]

Two studies comparing swan-neck and straight Tenckhoff catheters have shown a similar risk for peritonitis and exit infection, but less cuff extrusion, with the swan-neck design. The lower incidence of cuff extrusion enhances the survival of the swan-neck catheters. ^{[157] [158] [159]} A technique that modifies the swan-neck catheter to a presternal exit site location has been reported by Twardowski and colleagues ^{[160] [161]} and has shown an increase in access survival up to 95% at 2 years. It has shown a decrease in peritonitis, exit wound infection. The authors advocate the use of the catheter in obese patients, patients with ostomies, children with diapers and fecal incontinence. Gadallah and colleagues^[162] demonstrated that placement of PD catheters by peritoneoscopic approach had a longer survival rate than those placed surgically, and the rates of exit infection and leak were lower. Moncrief and associates^[151]described a technique in which the extraperitoneal portion of the catheter is buried in the abdominal subcutaneous tissue until the patient is ready for PD. It appears that it lowers the risk for initial infection of the tract.^[151] A major complication during placement of the catheter is bowel perforation. It is infrequent with all techniques except for blind placement, but once identified, it requires bowel rest, intravenous antibiotic therapy, and rarely, surgical exploration. ^{[143] [152]} Tip migration is a very common (≤35%) late complication, which could cause problems with draining of the PD fluid. It can be fixed with either radiologic or surgical manipulation. ^{[163] [164]} PD leaks around the catheter have been reported as much as 10%, but the use of double-cuff swan-neck catheters have decreased the incidence.^[165] Perioperative infection and bleeding are very rare; prophylactic antibiotics are usually given.^[164]

Technical Procedure: Insertion of Peritoneal Catheters by Fluoroscopic and Ultrasound Techniques

The abdomen is prepped and draped in a sterile fashion. Conscious sedation is administered with midazolam hydrochloride and fentanyl citrate. A registered nurse obtains vitals signs and administers the conscious sedation during the procedure. Insertion site is selected to be 2 cm to the left or right and below the umbilicus. An ultrasound machine with a properly sterilely covered 5-MHz transducer is used to guide a 21-gauge needle into the peritoneum. Under ultrasound guidance, the needle penetrates through the skin, the subcutaneous tissue, the outer fascia of rectus muscle, the muscle fibers, the inner fascia, and the parietal layer of peritoneum. Three to 5 mL of contrast is injected into the peritoneal cavity under fluoroscopy to ensure appropriate location; a radiologic pattern of bowel delineation is indicative of a good placement. A 0.018-inch cope-mandrel-wire is introduced through the needle. The needle is exchanged for a 6-French catheter sheath. A 2-cm incision is made on the skin, and the subcutaneous tissue is digitally dissected up to the rectus muscle. A series of dilators (8, 12, and 14 French) are passed over a stiff glidewire, and an 18-French peel-away sheath is placed. A double-cuff, swan-neck, Tenckhoff PD catheter is introduced over the stiff glidewire into the peritoneal cavity. The coiled intraperitoneal portion is placed in the lower intra-abdominal area. The inner cuff is pushed into the muscle before the peel-away sheath is removed. A tunnel is created with an exit site located distal, lateral, and below the initial incision with the outer cuff buried in the subcutaneous tissue. A final fluoroscopic imaging is performed to verify placement of the Tenckhoff catheter ( Fig. 28-17 ). Inflow and outflow of the PD catheter is tested with 500 mL of normal saline. The PD catheter is flushed with 10 to 15 mL of heparin. The subcutaneous tissue and skin are sutured, and the site is dressed.

FIGURE 28-17 A, Spot film demonstrates free flow of contrast injection into the peritoneal cavity. B, Spot film shows a peel-away sheath in place during insertion of a Tenckhoff catheter. C, Spot film shows appropriate placement of a Tenckhoff catheter.

Technical Procedure: Insertion of Peritoneal Catheters by Peritoneoscopic Technique

Peritoneal catheters placed peritoneoscopically are implanted through the rectus muscle using a peritoneoscope device. It has the same initial preparation as for the fluoroscopic/ultrasound technique. With the patient under local anesthesia, a 2-cm skin incision is made. The subcutaneous tissue is dissected up to the rectus muscle. A catheter guide is inserted into the abdomen and the peritoneoscope is placed into the catheter to assess initial entry to the peritoneal cavity. The scope is removed, and 500 mL of air is infused into the cavity. The scope is again replaced and advanced to the pelvic area. This area is inspected for adhesions and bowel loops. The scope is again removed, and the peritoneal catheter is introduced through the catheter with the help of a stainless steel stylette. The catheter is advanced to the pelvic area. The stylette is removed, and the inner cuff is buried into the musculature. The exit location is determined, and the catheter is tunneled to that location.

Technical Procedure: Insertion of Peritoneal Catheters by Pre-Sternal Catheter Placement

The PD catheter implantation technique is the same as the peritoneoscopic insertion, except that the PD catheter has a straight design instead of a swan neck. After the PD catheter is placed, then a second catheter is tunneled from the midabdomen up to the chest wall. The two catheters are connected by a titanium joint piece. The second catheter has the swan-neck design and two cuffs. The exit site is located lateral to the midsternal line.

PERCUTANEOUS RENAL BIOPSY

Percutaneous renal biopsy is an important procedure in the diagnosis of renal disease. The results of a renal biopsy are helpful in guiding medical therapy and providing a prognosis. The goal of a renal biopsy should be to maximize the yield of adequate renal tissue while minimizing the risk of complications. Percutaneous renal biopsies have evolved from a blind procedure to a real-time ultrasound-guided needle biopsy. Although some nephrologists still use the Franklin-Silverman needle and the Tru-Cut needle for blind biopsy, several authors have documented that the use of real-time ultrasonography along with the use of an automatic biopsy gun minimizes complications and provides a high yield of adequate tissue for pathologic diagnosis ( Table 28-14 ). Cozens and co-workers^[166] retrospectively compared a 15-gauge Tru-Cut renal biopsy with ultrasound localization and marking with an 18-gauge, spring-loaded gun renal biopsy under real-time ultrasound guidance. They reported a 79% yield of adequate renal tissue with the blind technique compared with 93% with real-time ultrasound guidance.^[166] Similarly, two other comparative studies reported a higher mean number of glomeruli from biopsies obtained under real-time ultrasound compared with those performed blindly. ^{[167] [168]}

TABLE 28-14 -- Adequacy of Kidney Tissue Retrieval and Complications by Real-Time Ultrasound-Guided Percutaneous Renal Biopsy

Reference	Biopsies (N)	Adequate Tissue (%)	Major Complications[*] (%)
Maya et al, 2007[185]	65	100	0
Doyle et al, 1994[186]	86	99	0.8
Hergesell et al, 1998[187]	1090	98.8	<0.5
Donovan et al, 1991[188]	192	97.8	<1
Burstein et al, 1993[168]	200	97.5	5.6
Cozens et al, 1992[166]		93	N/A
Marwah and Korbet, 1996[169]	394		6.6

N/A, not available.

*	Definitions of major complications differed among studies.

Major complications of renal biopsies, including gross hematuria or retroperitoneal hematoma requiring blood transfusion, invasive procedure, or surgical intervention, have been reported in less than 1% of biopsies in some series and 5% to 6% by others (see Table 28-14 ). The likelihood of major complications was not associated with patient age, blood pressure, or serum creatinine in one large series.^[167] Among those patients with major complications, the time interval from biopsy to diagnosis of the complication was 4 hours or less in 52%, 8 hours or less in 79%, and 12 hours or less in 100% of patients.^[167] Thus, the minimal period of observation after a renal biopsy should be 12 hours. Minor complications, including transient gross hematuria or perinephric hematoma not requiring transfusion or intervention, occurred after 6.6% of biopsies in one series.^[169] Either ultrasound or computed tomography can be used to diagnose perinephric hematomas.^[170] Most hematomas resolve spontaneously within a few weeks with no significant sequelae. Major bleeding complications that do not resolve with conservative measures require further intervention. In the past, this entailed urgent surgical nephrectomy. However, selective renal arteriogram with embolization of the bleeding arteriole is often able to stop the bleeding in most cases. A review article reported only 0.3% major complications and less than 0.1% death rates in 9595 percutaneous renal biopsies performed over the last 50 years.

For patients at high risk of bleeding complications or liver disease with coagulopathy in whom a kidney biopsy is indicated, a transjugular kidney biopsy may be performed by an interventional radiologist or nephrologist. Thompson and colleagues^[171] reported 91% adequate tissue retrieval with an average of 9 glomeruli for light microscopy in 23 patients undergoing transjugular renal biopsy. A capsular perforation was encountered in 17 patients, of whom 6 required coil embolization of the bleeding vessel. Two major complications were reported, 1 arteriocalyceal system fistula and 1 renal vein thrombosis 6 days after the biopsy.^[171] Abbott and co-workers^[172] reported a series of nine patients undergoing transjugular renal biopsy. Adequate tissue was obtained from all patients. Capsular perforation occurred in 90% of the patients, and two patients developed gross hematuria requiring transfusion.^[172]

A bleeding disorder is an absolute contraindication to performing a percutaneous renal biopsy. However, if it can be corrected medically, and if the benefit of doing a biopsy outweighs the potential risk, the biopsy can still be performed, Some relative contraindications to renal biopsy include a solitary kidney, pyelonephritis, perinephric abscess, uncontrolled hypertension, hydronephrosis, polycystic kidney disease, severe anemia, pregnancy, renal masses, and renal artery aneurysms.

Technical Procedure: Percutaneous Renal Biopsy Under Real-Time Ultrasound Guidance

A complete blood count, prothrombin time, and partial thromboplastin time are checked before the procedure. The patient is taken to the ultrasound suite and placed in the prone position. An initial ultrasound examination is performed to confirm the presence of two kidneys. Sterile technique is observed and sterile cover placed over the ultrasound probe. The lower pole of the left kidney is preferred for right-handed operators. The skin and subcutaneous tissue are anesthetized with 1% lidocaine. A small incision is made with a scalpel at the site of needle insertion. Under real-time ultrasound guidance, a biopsy needle gun is advanced up to the capsule of the kidney ( Fig. 28-18 ). The patient is asked to hold his or her breath, and the spring-loaded gun is activated. The gun is retrieved, and the specimen is placed in a container with media. There are different types of needle biopsy guns: full-core, half-core, or three quarters of a core. Sizes vary from 14-French to 18-French and lengths vary from 10 to 20 cm. Also, the throw (amount of tissue that the gun can obtained) of the device can be adjusted from 13 to 33 mm. Usually two or three biopsy pieces are taken in one setting to provide enough tissue for light microscopy, immunofluorescence, and electron microscopy studies. After the biopsy is completed, a second-look ultrasound examination is performed to assess for perinephric hematomas ( Fig. 28-19 ). A color Doppler ultrasound postbiopsy surveillance imaging examination would also be helpful to localize any active bleeding ( Fig. 28-20 ). Vital signs are obtained frequently in the 1st hour and then every 2 to 4 hours. Hematocrits are checked every 6 hours for the next 24 hours.

FIGURE 28-18 Kidney ultrasound image shows a biopsy needle located at the lower pole of the kidney.

FIGURE 28-19 Postbiopsy kidney ultrasound image of a perinephric hematoma.

FIGURE 28-20 Postbiopsy kidney color Doppler ultrasound image shows active bleeding.

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