Multiple clinical guidelines have recommended prophylaxis for active removal of nephrolithiasis to prevent stone-related renal function deterioration. The surgical procedures to remove renal stones include standard percutaneous nephrolithotomy (sPCNL), mini percutaneous nephrolithotomy (mPCNL), and flexible Ureterorenoscopic lithostripsy (fURSL). The impact of PCNL on future renal function due to the inevitable loss of parenchyma while creating the nephrostomy tract during the surgery remains uncertain. Thus, the study is aimed to identify the impact of active stone removal on renal function.

This is a retrospective observational cohort study, enrolling 230 patients treated for nephrolithiasis, at a single tertiary medical center from 2013/11~2023/08. Patients were divided into sPCNL (n = 113), mPCNL (n = 40), and RIRS (n = 77) according to the operation methods. Serum creatinine (Cr) were measured before the surgery and during the last follow-up visit postoperatively. Renal function improvement was defined as post-operative (OP) CKD stage less than or equal to pre-operative CKD stage. Multivariate logistic regression models were used to assess predictive factors for renal function improvement.

153 patients underwent PCNL (66.5%), 113 of whom (73.9%) had sPCNL, and 77 patients received RIRS (33.5%). For pre-OP renal function, eGFR was 75.1±18.8 for sPCNL, 62.4±19.9 for mPCNL, and 67.6±23.6 for RIRS, which was statistically different. The three groups were compared in terms of BMI and underlying disease. Univariable logistic regression analysis showed higher BMI patients had better post-intervention renal function (OR 1.109, 95% CI 1.023-1.204, p = 0.013). This association remained significant after adjusting for age, gender, surgical type and hydronephrosis (OR 1.097, 95% CI 1.008-1.194, p = 0.031). After controlling for cofounding variables such as pre-OP CKD stage, stone size, multivariate logistic regression analysis revealed a significant correlation between obesity and the improvement in renal function after stone removal (OR 1.104, 95% CI 1.009-1.208, p = 0.031).

Regardless of the type of stone surgical procedure and whether or not there was pre-OP hydronephrosis, obesity is significantly associated with improved renal function after kidney stone removal.