Medstone 1050 ST Lithotripter: A Clinical Review

Abstract

This presentation compares the initial results of shock wave lithotripsy using the Medstone 1050 ST to the most recent clinical experience. This lithotripter employs a shock wave generator but eliminates the water bath, has computer drive positioning and can localize stones with either plain radiographs or ultrasound. This report compares the initial 325 patients with 551 urinary tract stones (Group I) to the most recent clinical experience of 342 patients (Group II). In Group I 64% of stones were smaller than 10 mm; 27% were 10 mm to 20 mm, and 9% were larger than 20 mm. Sixty-one percent of stones were calyceal, 26% pelvic, and 13% ureteral. Successful fragmentation, defined as no residual fragments larger than 4 mm, was achieved by 90.2% of patients and 92.4% of individual stones, including a retreatment rate of 4%. For the entire group the stone-free rate was 78%; however, it was 85% excluding stones larger than 20 mm No significant variation of the success rate could be related to patient weight, stone size, or location. Follow-up evaluation revealed no clinically significant laboratory abnormalities. The average hematocrit change was from 42% to 39%, possibly because of hemolysis. Only two hematomas were found on ultrasound and no transfusions were administered. Renal colic occurred in 8% of cases, and temporary obstruction occurred in 14% of patients. Renal scans or excretory urograms were performed at three months in Group I. Two treated kidneys were found to have diminished function, one of which returned to normal in 30 days. One patient experienced hypertension which required medical treatment. Comparing Group I patients to Group II patients, the results were essentially the same.