Q. A 51-year-old man is referred to the one-stop haematuria clinic with occasional left loin ache and microscopic haematuria. He is otherwise well and takes no regular medication. Examination is unremarkable. His GP has requested a plain abdominal film. What does the KUB x-ray in Figure 10.3 show?
A. The x-ray in Figure 10.3 shows a 1.2 cm left lower pole calculus.
Q. He asks you what treatment options there are for the stone in the left kidney. What is the success rate of ESWL?
A. Available treatment options for this patient include ESWL, PCNL or flexible URS.
Lingeman et al. [7] reported the results of a meta-analysis that showed that the overall stone-free rate for ESWL when applied to lower pole stones (LPSs) was 59%, whereas ESWL for upper and middle pole calyces had a stone-free rate of up to 90%.
Stratified by stone size, LPSs fair worse than other sites. The meta-analysis showed stone- free rates for LPS (using ESWL), as follows:
|
Up to 10 mm |
74% |
|
11-20 mm |
56% |
|
Over 20 mm |
33% |
the European Association of Urology (EAU) 2017 treatment algorithm for renal stones [8] is summarised in Figure 10.4. LP stones >20 mm should be treated primarily by PCNL because ESWL will often require multiple treatments and it is associated with an increased risk of ureteric obstruction (steinstrasse) with the need for additional procedures. URS should only be offered as first line for these stones if the patient is not suitable for PCNL, with the down side of reduced SFRs and the need for staged procedures. LP stones between 10 and 20 mm with unfavourable factors for ESWL should be offered either URS or PCNL. LP stones under <10 mm can be offered ESWL or URS as primary treatment options.
Figure 10.3
Figure 10.4 The EAU 2017 treatment algorithm for renal stones.
Q. Are there any factors that predict outcome with ESWL?
A. Clearance after ESWL may be influenced by lower pole collecting system anatomy. Sampaio and colleagues first described the spatial anatomy of the lower pole as a possible factor in stone passage [9].
The following factors negatively impact the stone-free rates for LP stones:
Steep infundibular-pelvic angle
Long calyx (>10 mm)
Narrow infundibulum (<5 mm)
Shockwave-resistant stones (calcium oxalate monohydrate, brushite or cystine)
Different studies address calculation of predictive angles in different ways, however, making direct comparison of results problematic.
Keeley et al. [10] measured the LIP (lower pole infundibulopelvic) angle as the angle created by the lower border of the pelvis with the medial border of the lower pole infundibulum. One hundred and sixteen patients underwent ESWL for LPS. The LIP angle was the only factor to attain significance in predicting stone-free status.
Elbahnasy et al. [11] published a retrospective study of 159 patients undergoing ESWL, PCNL and URS for LPS. These authors used an alternative method for measuring the angle between two lines: the central point of the renal pelvis to the central point of the proximal ureter - to determine the ureteropelvic axis and the central axis of the lower pole infundibulum. In this study, all patients with three favourable factors (LIP greater than 70°, infundibular length less than 3 cm, and width greater than 5 mm) became stone free. Conversely, in patients with a combination of three unfavorable factors only 16% became stone free. These data must be interpreted with caution, however, as results from other studies have provided conflicting evidence.
It is intuitive that an obtuse versus an acute angle in LPS is important in fragment clearance after ESWL, but further prospective randomised studies are required to clearly determine the role of intrarenal anatomy.
Q. Is there anything else which can be done to improve the efficiency of stone clearance after ESWL for LPS?
A. Pace et al. [12] described percussion, diuresis and inversion (PDI) to enhance stone-free rates. Three months after ESWL 69 patients with residual lower calyceal fragments <4 mm were randomised to either mechanical percussion and inversion or observation for 1 month. They were treated with a mechanical chest percussor applied to the flank while inverted to greater than 60° after receiving 20 mg furosemide. Thirty-five patients had PDI and 34 observation. In the observation group 28 subsequently received mechanical percussion and inversion after completing the observation period. Stone-free rates were PDI 40% versus 3% observation.
Q. Are there any studies which compare ESWL, URS and PCNL for LPS?
A. ESWL was compared with PCNL in the ‘Lower Pole I’ study, published in 2001 [13]. This was a prospective, randomised, multicentre trial comparing PCNL and ESWL for LPS smaller than 30 mm. One hundred and twenty-eight patients were randomised to undergo PCNL (60) and ESWL (68). Three-month stone-free rates overall were 95% for PCNL and 37% for ESWL. The direct comparison of stone-free rates, stratified by stone size is shown in Table 10.1.
Table 10. The direct comparison of stone-free rates, stratified by stone size
|
Overall |
<10 mm |
11-20 mm |
21-30 mm |
|
|
ESWL |
37% |
63% |
23% |
14% |
|
PCNL |
95% |
100% |
93% |
86% |
Retreatment and ancillary rates in the ESWL and PCNL groups were 31% and 11%, respectively. The overall morbidity of both procedures was thought to be low.
Reported complication rates were 12% and 23% for ESWL and PCNL, respectively. Cost analysis has revealed PCNL and ESWL were equally effective for stones less than 10 mm, PCNL was more cost-effective for larger stones. The authors suggested that PCNL should be considered the primary approach for LPS larger than 10 mm. The drawback of this study is that URS was not considered.
This issue was addressed in the subsequent ‘Lower Pole II’ study [14]. Seventy-eight patients with 1 cm or less isolated lower pole stones were randomised to ESWL or URS. The operative time was significantly shorter for ESWL than URS. Intraoperative complications occurred in one ESWL case (unable to target stone) and in seven URS cases (failed access in five and perforation in two patients). This study did not show a statistically significant difference in stone-free rates between ESWL and URS for LPS, even though URS was 15% better. However, with continuing improvements in ureteroscopic technology and a study with a larger number of participants, a different outcome may be achieved if such a study were to be repeated. The Percutaneous nephrolithotomy, flexible Ureterorenoscopy and Extracorporeal shockwave lithotripsy (PUrE) study was There fore set up in the United Kingdom in 2015 to determine the clinical effectiveness and cost-effectiveness of the treatments for lower pole stones (URS versus ESWL for stones <10 mm and URS versus PCNL for stones >10 mm <25 mm) and will report their findings in 2020 [15].
URS could be proposed as the primary approach or as a less morbid treatment modality for patients with LPS who failed ESWL rather than proceeding to PCNL. The success rate (including ‘insignificant’ residual fragments) of URS for LPS is relatively high, with an average of 86% SFR for LPSs larger than 20 mm.
Anatomy of the lower pole may affect the results of URS for LPS, in a similar manner to ESWL as an acute angle may prevent passage of the laser fibre to the stone by limiting flexion.
ESWL is the preferred initial approach for most patients with LPS smaller than 1 cm, as it is a less invasive approach, not requiring general anaesthesia. Patients who failed ESWL, and patients known to have stones resistant to ESWL should be treated with PCNL or URS having considered the risks and benefits after an informed discussion with their urologist.
In contrast to URS and ESWL results, PCNL outcomes are independent of stone size and renal anatomy.
Q. Should a JJ stent be placed before considering ESWL in this patient?
A. Routine stenting is contraindicated prior to ESWL, and should be avoided.