Variation in the incidence of and risk factors for the development of nephrolithiasis after radical or partial nephrectomy

OBJECTIVE: To examine incidence of and risk factors for the development of nephrolithiasis in patients treated with radical nephrectomy (RN) or partial nephrectomy (nephron-sparing surgery, NSS). PATIENTS AND METHODS: The study comprised a single-centre review of 749 patients treated with RN or NSS from August 1987 to June 2006. Demographics, medical and stone history, metabolic variables and postoperative stone events were recorded. Data were analysed within subgroups based on treatment (RN vs NSS). Multivariate analysis was used to identify risk factors for postoperative stone formation. RESULTS: In all, 499 patients had RN and 250 had NSS (mean age 57.9 years; mean follow-up 6.3 years). There were no significant differences in their demographic factors, but tumours were significantly larger in RN (P < 0.001). There was no significant difference in preoperative urinary pH < 6.0 or stone history. Significantly fewer patients after NSS than RN formed calculi (NSS 1.6% vs RN 8.4%, P < 0.001), developed hypobicarbonataemia (NSS 7.2% vs RN 12.8%, P = 0.020), and a urinary pH of <6.0 (NSS 11.2% vs RN 19.4%, P = 0.004). Multivariate analysis showed that RN (odds ratio 18.18), postoperative urinary pH < 6 (15.63), previous stone disease (13.7), age <60 years (7.33, all P < 0.001), body mass index ≥30 kgm² (3.26, P = 0.033), male gender (2.67, P = 0.039), and hypobicarbonataemia (2.46, P = 0.034) were significantly associated with the development of postoperative calculi. CONCLUSION:S Patients undergoing RN have a significantly higher incidence of postoperative nephrolithiasis than a well-matched cohort undergoing NSS. In addition to RN, male sex, urinary pH < 6.0, hypobicarbonataemia, history of stone disease, obesity, and age <60 years were significantly associated with postoperative stone formation.