A Retrospective comparative analysis of postoperative renal function modification following retrograde intrarenal surgery versus minimally invasive percutaneous nephrolithotomy (≤ 26Ch) using serum creatinine-based metrics

Background and objective: Acute Kidney Injury (AKI) and Acute Kidney Disease (AKD) are underreported complications of minimally invasive surgeries for stone disease. There is a lack of data on differences in AKI and AKD rates following Retrograde Intrarenal Surgery (RIRS) compared to Minimally Invasive Percutaneous Nephrolithotomy (mPCNL) ≤ 26Ch. To compare the modification of renal function and the rates of AKI and AKD following RIRS versus mPCNL. Methods: We retrospectively analyzed data of patients treated between 2009 and 2025 across three tertiary referral centers. Renal function was evaluated using the CKD-EPI formula. Postoperative AKI and AKD were defined according to KDIGO criteria. Multivariable linear regression analysis assessed the association between surgical approach and postoperative eGFR change, adjusting for age, sex, comorbidities, stone characteristics, operative time, and baseline eGFR. Logistic regression models evaluated the risk of AKI and AKD. Adjusted percentage changes in eGFR were visualized using LOESS smoothing stratified by procedure and baseline eGFR. The onset of AKD was assessed both as a continuous variable at 3 months and as a binary variable according to the international definitions. Results: Of 606 patients, 414 (68%) underwent RIRS and 192 (32%) mPCNL. Compared with RIRS, mPCNL patients had larger stones (25 vs 11 mm, p < 0.001), longer operative times (100 vs 70 min, p < 0.001), and similar eGFR (85 vs 82 mL/min/1.73 m2, p = 0.8). No difference in eGFR change from baseline was observed (β = 2.3; 95% CI -6.7–11, p = 0.6), and no significantly higher risk of AKI (OR = 0.44; 95% CI 0.18–1.01; p = 0.059) between the two groups. Patients with lower baseline eGFR showed greater improvement at loess function assessment. AKD occurred in 11% of RIRS and 4.3% of mPCNL cases with known 3-months eGFR (p = 0.051). Conclusion: Overall, neither RIRS nor mPCNL was associated with a higher risk of postoperative AKI, with similar findings for AKD. These findings suggest that, within the limitations of this retrospective analysis, RIRS and mPCNL were associated with similar postoperative trends in renal function. However, these results should be interpreted cautiously and do not support treatment decision-making based solely on renal functional considerations.