Kelly A. Healy, MD
Demetrius H. Bagley, MD, FACS
BASICS
DESCRIPTION
• Hydronephrosis includes dilation of the renal pelvis and calyces while hydroureteronephrosis is dilation of the renal pelvis, calyces, and ureter
• Both can result from obstructive and nonobstructive causes
• Intrinsic and extrinsic obstructive process can affect the entire urinary tract
• Obstructive uropathy indicates impedance of urinary flow anywhere along the urinary tract, upper or lower and damage to the renal parenchyma due to obstruction at any site
EPIDEMIOLOGY
Incidence
Asymptomatic, unilateral hydronephrosis occurs in ∼3% of population
Prevalence
• 3.1% prevalence in historic autopsy series of 59,000 patients
– Age 20–60 more common in women, secondary to pregnancy/gynecologic conditions
– Age >60 yr obstruction more common in men (6.2% vs. 2.9%) attributed to prostatic diseases
• A similar 2.5% prevalence of asymptomatic unilateral hydronephrosis in radiologic series among potential renal donors
– More women than men (86% vs. 14%)
– No association with potential donor age
RISK FACTORS
• Urolithiasis is most common cause of upper urinary tract obstruction, prevalence between 10–15% by age 70 yr
• Ureteropelvic junction (UPJ) obstruction can occur from anatomic-crossing vessel, high insertion, or secondary conditions (impacted stone)
• Lower urinary tract disorders can result in hydroureteronephrosis, often bilateral
• Benign prostatic enlargement is the most common affecting 70% of men by age 70
• Hydronephrosis can develop with obstructive lesions at essentially any level.
• Kidney:
– Benign lesions including peripelvic cysts
– Malignant neoplasms with renal cell carcinoma and urothelial carcinoma
– Renal pelvic calculi
– UPJ obstruction
– Infection tuberculosis
– Renal artery aneurysm
– Hilar lymphadenopathy
• Ureter:
– Neoplasms: Benign papilloma, fibroepithelial polyp, ureteritis cystica; malignant urothelial carcinoma
– Ureteral calculi or stricture
– Ureterocele or congenital megaureter
– Infection (tuberculosis, schistosomiasis)
– Retroperitoneal lymphadenopathy (lymphoma, other malignancy)
– Inflammatory (retroperitoneal fibrosis and arterial aneurysms)
– Gynecologic: Ovarian vein syndrome, endometriosis, GYN malignancy, pregnancy
– Pelvic lipomatosis
– Retrocaval ureter
• Bladder/urethra:
– Malignant neoplasms: eg, urothelial carcinoma locally advanced carcinoma of the prostate
– Bladder neck contracture
– Prostatic obstruction
– Detrusor dysfunction
– Increasing intravesical storage pressure
– Urethral stricture; meatal stenosis
– Phimosis
Genetics
Nonobstructive hydronephrosis occurs with several congenital syndromes, usually diagnosed in infancy (see “Hydronephrosis/Hydroureteronephrosis, Pediatric”)
PATHOPHYSIOLOGY
• Effective hydroureteronephrosis on renal function depends on whether it is totally or partially obstructive and unilateral or bilateral
• Effects of obstruction of the kidney are time dependent. Within several hours, changes are evident but (1)
– 1–2 wk—glomerular destruction, tubular atrophy, and interstitial fibrosis occur
– By 6–8 wk irreversible damage occurs
ASSOCIATED CONDITIONS
Numerous causal conditions can be associated. See “Risk Factors” above.
GENERAL PREVENTION
Hydronephrosis may be disease related and prevention then must be individualized
DIAGNOSIS
HISTORY
• Signs and symptoms vary dependent on the etiology and chronicity of the condition
• Acute obstruction can cause abdominal flank and/or back pain; may be associated with anorexia, nausea, vomiting
• Gradual ureteral obstruction more typically presents with vague complaints or may be asymptomatic
• Insidious obstruction of solitary kidney or bilateral can present with symptomatic obstructive uropathy or evidence of renal compromise
• Complete urinary history is essential
• Site of obstruction, upper vs. lower urinary tract may relate to presentation
– Upper urinary tract—flank pain and costovertebral angle tenderness with acute obstruction
– Lower urinary tract maybe associated with obstructive voiding symptoms
PHYSICAL EXAM
• General condition—pain or localized symptoms
• Hypertension can be related to obstruction
• Abdominal, flank, or pelvic mass
• Flank tenderness can occur with acute obstruction and with calculi or infection (pyelonephritis, pyelonephrosis, retroperitoneal abscess)
• Vaginal exam
– Ureteral prolapse
– Ureterocele through urethra
• Digital rectal exam
– Enlarged prostate, nodularity suggestive of prostate cancer
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urinalysis for hematuria, pyuria, crystalluria
• Urine culture
• Renal function studies:
– BUN & creatinine
• CBC
– Anemia—associated with chronic renal insufficiency
– Elevated white blood cell count with infection
• Serum chemistries, special attention to potassium
• Serum prostatic-specific antigen (PSA)
• Urine cytology for urothelial carcinoma
Imaging (2)
• Several modalities are available. They differ in their degree of anatomic and functional information and may distinguish the presence and extent of obstruction.
• Renal ultrasound: Inexpensive, widely available, no ionizing radiation, and no contrast (3)
– Excellent to define hydronephrosis
– Should include imaging through the bladder to assess for distal hydroureter, ureteral jets, bladder wall thickening, and postvoid residual
– Renal cortex can be evaluated
• Color Doppler renal ultrasound (4):
– Help distinguish obstructive vs. nonobstructive hydronephrosis
– Resistive index (RI) = (PSV – EDV)/PSV (peak systolic velocity end diastolic velocity)/peak systolic velocity
RI ≥0.7 suggested of obstruction (92%) sensitivity and (88%) specificity
RI is time dependent and decreases >48 hr after obstruction. Thus, less useful for chronic vs. acute obstruction
• Noncontrast CT scan:
– Imaging of choice for acute renal colic
– Visualizes entire urinary tract and adjacent structures; best for urolithiasis and may not detect soft tissue masses or filling defects
– Secondary signs of acute obstruction include perinephric stranding and nephromegaly
– Normal ureter on unenhanced CT is considered to be 3 mm in adults
• CT urogram
– Good for incidental hydronephrosis
– Noncontrast phase for ureterolithiasis
– Contrast phase-delayed nephrogram suggested obstruction
– Defined parenchymal masses, evaluate for crossing vessels with UPJ obstruction
– Delayed (excretory) phase may look like site of obstruction and rule out filling defect depending on degree of renal impairment
• Excretory urogram:
– Generally replaced by CT urogram
• Magnetic resonance imaging (MRI)
– Lack of ionizing radiation advantageous for children, pregnant patients, and those with renal insufficiency or contrast allergy
– More time consuming, expensive, does not effectively image urolithiasis
• Pyelography: Antegrade or retrograde
– Can be used with ultrasound or noncontrast CT in patients with contrast allergies or renal insufficiency; but invasive
• Functional studies to differentiate obstructive vs. nonobstructive uropathy
– Whitaker test: 1st described in 1980
Indwelling percutaneous nephrostomy tube
Percutaneous puncture renal pelvis
Upper urinary tract is perfused at a rate of 5–10 mL per minute with saline or contrast media
Serial pressure recording is made in renal pelvis and bladder; spot films aid in evaluation
Pressure gradient: Obstruction >22 cm H2O; equivocal 15–22 cm H2O; normal <15 cm H2O
– Nuclear renography:
Primary noninvasive study to distinguish obstructive vs. nonobstructive uropathy
DTPA: Freely filtered by glomerulus. Neither secreted nor resorbed by renal tubules
MAG-3: Almost exclusively limited by proximal tubule secretion without resorption distally
Preparation of patient, maintain hydration, place a Foley catheter if concern for lower urinary tract dysfunction or obstruction
Furosemide 20–40 mg given 20 min after radiotracer administration to induce diuresis
Half time (T½ clearance). Time it takes to eliminate 50% of radiotracer: Obstruction >20 min; equivocal >10–20 min; normal <10 min; false positives: More commonly with severe dilation or poor function
• Endoluminal ultrasound (ELUS):
– Evaluate periureteral anatomy, vessels of high insertion and UPJ obstruction, define ureteral stricture
– Study of choice for submucosal calculi
• Voiding cystourethrogram (VCUG):
– Evaluate for reflux
– Patients with recurrent urinary tract infections, flank pain, nonobstructive hydronephrosis
Diagnostic Procedures/Surgery
Cystoscopy, retrograde ureteropyelogram
Pathologic Findings
Nephropathy related to obstruction (see above)
DIFFERENTIAL DIAGNOSIS
• Obstructive vs. nonobstructive hydroureteronephrosis
• See also “Risk Factors”
TREATMENT
GENERAL MEASURES
• Management is highly dependent on underlying condition and the timing (acute vs. chronic)
• Urgent decompression is needed with:
– Severe pain
– Active urinary tract infection and acute kidney insufficiency
– Retrograde ureteral stent or percutaneous nephrostomy can provide equally effective drainage
• Hydronephrosis lower urinary tract etiology is typically bilateral and patients may be asymptomatic
• May warrant catheter drainage or endoscopic treatment
MEDICATION
First Line
• Patients with infection and hydronephrosis require antibiotic therapy and drainage
– Renal failure and electrolyte abnormalities should be corrected in conjunction with drainage
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Catheter drainage of obstructed system with percutaneous nephrostomy or ureteral stent is guided by the severity of the illness
– Hydronephrosis and fever may be ominous signs requiring early drainage
– Other surgical procedures can be guided by the findings on imaging studies
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
Hemodialysis may rarely be needed in the acutely ill patient
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
Cause specific
COMPLICATIONS
• Progressive renal deterioration
• With vesicoureteral reflux, scarring and hypertension can occur
• Postobstructive diuresis seen only with bilateral obstruction or solitary functioning kidney
FOLLOW-UP
Patient Monitoring
• The etiology for hydronephrosis will determine the appropriate surveillance regimen
• Consider renal ultrasound and renal scan at 3 mo after treatment
• Postoperative imaging may demonstrate the dilatation persists despite relief of obstruction
Patient Resources
N/A
REFERENCES
1. Arena S, Magno C, Montalto AS, et al. Long-term follow-up of neonatally diagnosed primary megaureter: Rate and predictors of spontaneous resolution. Scand J Urol Nephrol. 2012;46:201–207.
2. Patatas K, Panditaratne N, Wah TM, et al. Emergency department imaging protocol for suspected acute renal colic: Re-evaluating our service. Br J Radiol. 2012;85:1118–1122.
3. Jandaghi AB, Falahatkar S, Alizadeh A, et al. Assessment of ureterovesical jet dynamics in obstructed ureter by urinary stone with color Doppler and duplex Doppler examinations. Urolithiasis.2013;41:159–163.
4. Piazzese EM, Mazzeo GI, Galipò S, et al. The renal resistive index as a predictor of acute hydronephrosis in patients with renal colic. J Ultrasound. 2012;15:239–246.
ADDITIONAL READING
Shapiro SR, Wahl EF, Silberstein MJ, et al. Hydronephrosis Index: A new method to track patients with hydronephrosis quantitatively. Urology. 2008;72:536.
See Also (Topic, Algorithm, Media)
• Hydronephrosis/Hydroureteronephrosis, (Dilated Ureter/Renal Pelvis), Adult Image 
• Hydronephrosis/Hydroureteronephrosis, (Dilated Ureter/Renal Pelvis), Pediatric
• Ureter, Obstruction
• Urolithiasis, Ureteral
CODES
ICD9
• 591 Hydronephrosis
• 592.0 Calculus of kidney
• 600.00 Hypertrophy (benign) of prostate without urinary obstruction and other lower urinary tract symptom (LUTS)
ICD10
• N13.2 Hydronephrosis with renal and ureteral calculous obstruction
• N13.30 Unspecified hydronephrosis
• N40.0 Enlarged prostate without lower urinary tract symptoms
CLINICAL/SURGICAL PEARLS
• Hydronephrosis and fever especially sepsis may require immediate drainage.
• Hydronephrosis may be nonobstructive.
• Generally hydronephrosis in an adult can be considered a sign of a process that must be defined and possibly treated.