Changes of renal function after retrograde intrarenal surgery using flexible ureteroscope in renal stone patients

Background: Retrograde intrarenal surgery (RIRS) is widely performed for renal stones. Theoretically, removing renal stones could prevent the deterioration of renal function. However, two studies reported that not all patients would see an increase in renal function after RIRS. The aim of our study was to evaluate the change of renal function of the operative site, and to identify predictors of improvement or deterioration of renal function after RIRS. Methods: We retrospectively reviewed renal stones patients who received RIRS and single-photon emission computed tomography (SPECT) before and after surgery. Improved renal function was defined as the change of glomerular filtration rate (GFR) >10% postoperatively, and that <-10% was regarded as deteriorated renal function. Logistic and least absolute shrinkage and selection operator regression analyses were used to identify predictors for the improvement or deterioration of renal function, and predictive nomogram models were built. Results: A total of 120 renal stone patients were included. Twenty-one (17.5%), 79 (65.8%) and 20 (16.7%) patients had improved, stable and deteriorated renal function of operative site after surgery, respectively. Lower alkaline phosphatase, lower low-density lipoprotein, lower GFR of the operative site, thicker renal parenchyma, higher serum creatinine, and extracorporeal shock wave lithotripsy (SWL) history were associated with the improved renal function. The predictive accuracy of the model for the improved renal function was 0.800. Additionally, older age, longer flexible ureteroscopic time, thinner renal parenchyma and existence of ureteral stones were risk factors for deteriorated renal function. The predictive accuracy of the model for the deteriorated renal function was 0.725. Conclusions: The renal function of most renal stone patients did not decrease after RIRS. For patients with potential deterioration of renal function postoperatively, urologists could shorten flexible ureteroscopic time to prevent the occurrence of this outcome.