Pelvicalyceal stone load: a factor affecting the outcome of extracorporeal shockwave lithotripsy for renal pelvic calculi

Objectives To determine the effect of variations in pelvicalyceal volume on the results of extracorporeal shock wave lithotripsy (ESWL) and the relationship of stone load to estimated pelvicalyceal volume in patients with renal pelvic stones. Patients and methods In all, 204 patients with renal pelvic stones were treated primarily by ESWL. Exclusion criteria were radiolucent stones, dilatation of the renal collecting system, JJ stent insertion before ESWL and an inadequate follow‐up. The surface area of the stones and the renal collecting system were measured using a grid of 1 mm 2 divisions. The pelvicalyceal volume was calculated as 0.6 (area) 1.27 . To evaluate the treatment results a pelvicalyceal stone load (PSL) index, describing the relationship of stone load to total estimated pelvicalyceal volume, was defined as stone volume/renal collecting system volume. Results The mean (range) pelvicalyceal volume of the patients was 13.24 (4.12–28.47) mm 3 and the mean PSL index was 26.2%. The cumulative success rates according to the PSL decreased from 97% to 90% with increasing PSL, but remained at > 95% in patients with a PSL index of < 50%. In all, 184 sessions were applied and the session/patient ratio increased from 1.41 to 3.0 with increasing PSL. Complications were acute pyelonephritis in three and steinstrasse in five patients. Conclusion The PSL index appears to be a more accurate and reproducible method for predicting the outcome of ESWL, and has the advantage of considering the effect of pelvicalyceal anatomy.