Factors affecting lower calyceal stone clearance after Extracorporeal shock wave lithotripsy

Objective: Extracorporeal shock wave lithotripsy (ESWL) is one of the most commonly used procedures to remove renal calculi from the lower calyces. The aim of this work is to study the impact of radiological, anatomical and demographic factors on stone clearance after ESWL of lower calyceal calculi. Patients and methods: This retrospective study included 150 patients aged between 16 and 70 years who were subjected to ESWL at October 6 University Hospital, Egypt, between June 2008 and October 2011. All the patients had solitary radio-opaque lower calyceal renal stones sized 2 cm or less. Intravenous urography (IVU) was performed to determine the patients’ lower-pole calyceal anatomy (infundibulum width, infundibulum length and the lower-pole infundibulopelvic angle). The patients who were divided into two groups according to the treatment results (Group 1: stone-free patients; Group 2: patients with residual fragments) were followed up for 3 months and re-assessed by plain X-ray. Results: A total of 126 patients (84%) were stone-free (Group 1), while 24 patients (16%) had residual fragments (Group 2). The stone size was 0.5–1 cm in 76 patients (60.3%) and 1–2 cm in 50 patients (39.7%) of Group 1, respectively, with no statistically significant difference. In patients with a lower-pole infundibulopelvic angle ≥45°, stone clearance was 52% compared to a stone clearance of 32% in patients with a lower-pole infundibulopelvic angle <45° with no statistically significant difference. Regarding the infundibulum length (<35 mm vs. ≥35 mm) and width (<4 mm vs. ≥4 mm), no statistically significant difference was observed between Group 1 and Group 2. Ninety out of 106 patients (84.9%) with a body-mass index (BMI) ≤30 kg/m2 were stone-free, compared to 36 out of 44 patients (81.8%) with a BMI > 30 kg/m2. Conclusions: There is no statistically significant effect of stone size, anatomy of the lower calyx and BMI on stone clearance after ESWL of lower calyceal stones. However, small stone size (≤2 cm), a shorter and wider infundibulum and a larger lower-pole infundibulopelvic angle seem to promote a more rapid and more complete stone clearance