OBJECTIVETo evaluate the factors affecting the efficacy of extracorporeal shock wave lithotripsy (ESWL) for renal calculi.

METHODSBetween January, 2004 and January, 2007, 316 patients (212 men and 104 women) with renal stone underwent ESWL. The correlations of the patients' age, gender, body mass index (BMI), disease course, pain, hematuria, stone size, location, side, number and hydronephrosis to the outcome of the treatment was analyzed. The treatment success was defined as complete clearance of the stones or residual stone fragments <0.4 cm, and ESWL was considered unsuccessful with residual stones>0.4 cm.

RESULTSThe overall success rate was 75.3% (238/316) in these patients. Significant difference in stone clearance rates was observed in patients with stone size of 0.5-1.0 cm (90.3%, 167/185), 1.0-2.0 cma(69.6%, 55/79), and >2.0 cm (30.8%, 16/52) (P<0.05). The success rates differed significantly between cases of pelvic stones (83.1%, 118/142) and those of caliceal stones (69.0%, 120/174) (P<0.05). But in cases of caliceal stones, the success rates were comparable between cases with stones at the upper calyx (71.7%, 43/60), middle calyx (68.9%, 31/45), and lower calix (66.7%, 46/69) (P>0.05). Patients with single stones had significantly higher success rate (82.9%,170/205) than those with multiple stones (61.3%, 68/111) (P<0.05). The patients' gender, age, disease course, pain, hematuria, stone side and hydronephrosis did not produce significant impact on the outcome of the treatment (P>0.05).

CONCLUSIONStone size, location and quantity are significant independent factors affecting the outcome of ESWL for renal stones.