Extracorporeal Shock Wave Lithotripsy for Lower Pole Calculi: Long-term Radiographic and Clinical Outcome

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Abstract
We evaluated the efficacy of extracorporeal shock wave lithotripsy (ESWL) for lower pole calculi regarding immediate and long-term radiographic and clinical outcomes. A total of 206 patients with isolated lower pole calculi in 220 renal units underwent ESWL for stones 4 to 625 mm2 (mean 88). Clinical and radiographic followup was obtained at 1 month and every 6 to 12 months thereafter. An initial stone-free rate was determined, as was the subsequent radiographic outcome. Clinical outcome with regard to a symptomatic episode or requiring intervention was also determined. Kaplan-Meier estimates of the probabilities of these outcomes with time were developed. Of the 206 patients 99 (48%) were rendered stone-free by 1 month after ESWL. Another 13 patients (6.3%) spontaneously became stone-free within another 1 to 95 months (mean 17.5). Of the remaining patients residual stones were decreased, stable or increased in 13 (6.3%), 71 (34%) and 10 (4.8%), respectively, after 1 to 91 months (mean 14.5). Among all 206 patients 180 (87.4%) remained asymptomatic for 1 to 99 months, while 7 (3.4%) suffered a symptomatic episode requiring medical attention 1 to 40 months (mean 21.1) after ESWL and 19 (9.2%) required intervention after 1 to 91 months (mean 23.9). Kaplan-Meier estimates of the probabilities of a symptomatic episode or requiring intervention at 5 years were 0.24 and 0.52, respectively. ESWL is the initial treatment of choice for lower pole calculi smaller than 2 cm.2 because the stone-free rate is comparable to that for stones at other caliceal locations and, perhaps more importantly, the risk of a symptomatic episode or requiring secondary intervention is low even in the setting of residual fragments.