The role of some risk factors in the prediction of stone recurrence after lithotripsy

The incidence of kidney stone recurrence after extracorporeal shock waves lithotripsy (ESWL) has to be re-valuated and the identification of potential risk factors, able to predict the recurrence, is under discussion. This prospective study, carried out on a homogeneous group of 520 patients (275 males, 245 females; aged 14-79 years), previously treated with ESWL for idiopathic calcium nephrolithiasis, allowed to estimate the incidence of recurrence (101 relapses; mean incidence of about 10% per year) with a long enough follow-up (23 months on average; median =24 months, range = 12-48 months). Multivariate statistical analysis performed to predict the recurrence by some possible risk factors, showed that age was inversely related to occurrence of the event (Relative Risk (RR) =0.9837; 95% CL=0.9689-0.9987) whereas urinary calcium (UC) (RR=1.0013; 95% CL=1.0003- 1.0022), alkaline phosphatase (AP), (RR=1.0048; 95% CL=1.0021-1.0074) and history of previous relapses (RR=1.5239; 95% CL=1.0226-2.2710) were directly related to the recurrence. The levels of UC were not correlated to those of AP (linear correlation coefficient r=0.0032), but the combination of their high levels increased the risk of recurrences.