Renal pelvis urine density as a predictor of infectious complications after semi-rigid ureterorenoscopy for ureteral stone treatment

Introduction: This study aimed to investigate whether renal pelvis urine density (RPUD) serves as a reliable predictor of postoperative infectious complications in patients undergoing semi-rigid ureterorenoscopy (URS) for ureteral stone treatment. Methods: We retrospectively reviewed 1104 patients who underwent semi-rigid URS for ureteral stones. Patients were divided into two groups based on whether they developed postoperative infections within one month (n=64) or not (n=1040). Demographic variables (age, sex, body mass index), comorbidities, stone characteristics (location, size, density), and operative parameters (operation time, stent/catheter placement) were recorded. Renal pelvis urine density was measured in Hounsfield units on preoperative imaging. Results: Of the 1104 patients, 64 (5.8%) developed postoperative infections. The median RPUD was significantly higher in the infectious group (10 5–17 HU) compared to the non-infectious group (4 2–6 HU; p=0.001). On multivariate analysis, sex (odds ratio OR 4.001, 95% confidence interval CI 2.231–7.174, p=0.001), body mass index (OR 0.920, 95% CI 0.860–0.984, p=0.015), operation time (OR 0.963, 95% CI 0.932–0.996, p=0.028), and RPUD (OR 0.809, 95% CI 0.771–0.849, p=0.001) were independent predictors of postoperative infection. The area under the curve was 0.784 (p<0.001, 95% CI 0.711–0.857), demonstrating good discriminative ability. When a cutoff value of 6.35 was applied, the sensitivity and specificity were 71.9% and 76.9%, respectively, for predicting postoperative infections. Conclusions: Higher RPUD is significantly associated with an increased risk of infectious complications following semi-rigid URS for ureteral stones. Incorporating RPUD into preoperative assessments may help identify high-risk patients and optimize perioperative management to reduce infection-related morbidity.