Impact of lower pole anatomy on stone clearance after shock wave lithotripsy

This study retrospectively analyzed patients treated with shock wave ithotripsy (SWL) for lower calyceal stones, to determine the influence of the lower pole anatomy and stone size in predicting the clearance of fragments. Between June 2000 and March 2002, we reviewed excretory urography (IVU) of 59 patients with isolated lower pole stones treated with SWL. A total of 44 men and 15 women, with an age ranging between 23 and 78 years (mean, 55 years), were included in the study. The patients were divided into two groups, either a stone-free group or residual-stone group. After SWL, overall stone rate was 57.6%, and clearance for stones less than 10 mm in diameter was 64.5%, whereas clearance was 50% for stones between 10 and 20 mm in diameter. Intrarenal anatomy on IVU, such as infundibular width and infundibulopelvi-ureteric angle showed no significant difference between the stone-free and residual-stone groups. Our analysis showed that three significant variables were relevant to stone clearance: infundibular length, stone size and stone burden. We conclude that SWL is the best treatment for lower pole kidney stones 10 mm or less in diameter, showing lower complication and acceptable stone-free rates.