Long-term incidence and risk factors for recurrent stones following percutaneous nephrostolithotomy or percutaneous nephrostolithotomy/extracorporeal shock wave lithotripsy for infection related calculi.

A study was done to determine the long-term incidence and cause of recurrent stones following percutaneous nephrostolithotomy alone (13 patients) or combined with extracorporeal shock wave lithotripsy (31) for management of documented infection related struvite renal calculi. The patients were followed for 12 to 111 months (mean 41.7) to censorship or time of new stone formation. Of these patients 12 (27%) had recurrent stones at 12 to 61 months (mean 32.3) after treatment. As determined by a Kaplan-Meier estimate, the risk of new stone formation 5 years after treatment was 36.8%. Potential risk factors for recurrence, including history of stones, associated anatomical abnormalities, procedure used, radiographic status at completion of treatment and recurrent infection during followup, were analyzed with Cox's proportional hazards model. Of these potential risk factors, only an associated anatomical abnormality was found to influence significantly the rate of recurrent stone formation (p = 0.005). We conclude that continued surveillance for recurrent stones is mandatory even for patients initially rendered stone-free and those who maintain sterile urine. In addition, because the presence of a significant anatomical or functional urinary tract abnormality places a patient at much higher risk for recurrence, we suggest that subsequent studies be stratified as to the presence or absence of these abnormalities.