Impact of renal anatomy on shock wave lithotripsy outcomes for lower pole kidney stones: Results from a prospective multifactorial analysis controlled by computed tomography scan - Abstract

PURPOSE: To evaluate which variables impact fragmentation and clearance of lower pole calculi after SWL.

PATIENTS AND METHODS: We prospectively evaluated patients undergoing SWL for solitary lower pole kidney stones ranging from 5-20mm between Jun-12 and Aug-14. Patient's BMI and abdominal waist circumference were recorded. One radiologist, blinded to SWL outcomes, measured stone size, area and density, stone-skin distance, infundibular length, width and height, and infundibulopelvic angle based on baseline noncontrast computed tomography (NCCT). Fragmentation, success (residual fragments < 4mm in asymptomatic patients) and stone-free rates were evaluated by NCCT 12 weeks post-operatively. Univariate and multivariate analysis were performed.

RESULTS: One hundred patients were enrolled. Mean stone size was 9.1mm. Overall fragmentation, success, and stone-free rates were 76%, 54%, and 37%, respectively. On logistic regression, BMI (OR 1.27, 95%CI 1.11-1.49; p=0.004) and stone density (OR 1.0026, 95%CI 1.0008-1.0046; p=0.005) impacted significantly on fragmentation. Stone size (OR 1.24, 95%CI 1.07-1.48; p=0.039) and stone density (OR 1.0021, 95%CI 1.0007-1.0037; p=0.012) impacted on success rate, whereas stone size (OR 1.24, 95%CI 1.04-1.50; p=0.029), stone density (OR 1.0015, 95%CI 1.0001-1.0032; p=0.046), and infundibular length (OR 1.1035, 95%CI 1.015-1.217; p=0.015) impacted on stone-free rate. The best outcomes were found for patients with BMI ≤ 30 Kg/m2, stones ≤ 10mm and ≤ 900 HU, and infundibular length ≤ 25mm. The coexistence of significant unfavorable variables led to a stone-free rate < 20%.

CONCLUSION: Obese patients with high-density stones (>900 UH) higher than 10mm located in the lower pole of the kidney with an infundibular length >25mm should be discouraged to perform SWL.

Written by:
Torricelli FC, Marchini GS, Yamauchi FI, Danilovic A, Vicentini FC, Srougi M, Monga M, Mazzucchi E.   Are you the author?
Division of Urology, Hospital das Clinicas, University of Sao Paulo Medical School, Sao Paulo, SP, Brazil; Stevan B. Streem Center for Endourology & Stone Disease, Glickman Urological & Kidney Institute, The Cleveland Clinic. Cleveland, OH, USA.  

Reference: J Urol. 2014 Dec 15. pii: S0022-5347(14)05078-2.
doi: 10.1016/j.juro.2014.12.026

PubMed Abstract
PMID: 25524240 Endourology Section