Assessing the efficiency of extracorporeal shockwave lithotripsy for stones in renal units with impaired function: a prospective controlled study

The objective was to determine the efficiency of extracorporeal shockwave lithotripsy (ESWL) in clearing stones from renal units with impaired function. Thirty-five patients with poorly functioning kidneys determined by intravenous urogram and ^99mtechnetium diethylene triamine pentacetic acid renal dynamic scan underwent ESWL. Stone clearance was assessed at 3 months and compared with that in normally functioning kidneys. The study group was divided into two subgroups. Those with split glomerular filtration rate (GFR) of the concerned kidney between 10 and 20 ml/min were in group 1. Group 2 consisted of patients with split GFR between 20 and 30 ml/min. A control group (group 3) was formed from patients with urolithiasis and normally functioning kidneys. The overall retreatment rate was 84.4%. The overall stone clearance rate in the study group was 34.2% while it was 57.7% in the control group. The stone clearance rate in group 2 was 40%. The difference in stone clearance rate between the study and control groups was statistically significant (P=0.023) but that between group 2 and the control group was not (P=0.159). The incidence of steinstrasse between the study group 2 and control group was not statistically significant (P=0.408). The clearance rate for ureteral stones was comparable in all the three groups. The stone-free rate and rate of steinstrasse for renal stones in kidneys with moderately impaired function were comparable to normally functioning kidneys. However, kidneys with severely impaired function had poor results. The clearance rate for ureteral stones was not influenced by the impairment of renal function.