A Single-Center Experience of the Usefulness of Caliceal-Pelvic Height in Three Different Lithotripters

Abstract

Stone-free rates for lower caliceal stones after Extracorporeal Shockwave Lithotripsy (SWL) are persistently poor. As stone-free rates vary with lithotripter type, we have compared the applicability of caliceal-pelvic height (CPH) in the prediction of stone clearance in patients treated with three different lithotripters within one center. Four hundred seventy adult patients with solitary, radiopaque, lower caliceal stones of size 6 to 10 mm receiving primary SWL between January 1992 and June 2002 were identified. They were treated with one of three lithotriptors: the Wolf Piezolith 2300, the Dornier MPL 9000, and the Dornier Compact Delta. Pretreatment intravenous urograms were reviewed and CPH, the vertical distance from the lowermost point of the calix to the highest point of the lower lip of pelvis, was measured. The primary end-point was stone-free status after 3 months. Adjusted odds ratios (AORs) of different potential predictor variables for the overall results and individual machines were estimated using multiple logistic regression. In the overall analysis, stone size and machine type were the only predictors associated with stone clearance. While smaller stones had better clearance overall, the MPL 9000 appears to have the best performance, followed by the Piezolith 2300. However, after patients were stratified into different machine subgroups, CPH became a significant predictor of stone-free rate for the Piezolith 2300 (AOR = 0.960; 95% CI 0.925, 0.960; P = 0.031), but not the other two machines. CPH was only useful in the prediction of lower caliceal stone clearance for the Piezolith 2300. Therefore the usefulness of one anatomic factor to assess treatment using one lithotripter may not be extrapolated to other machines.