[Effect of Body Mass Index on Outcomes of Mini-ECIRS for Renal Stone]

We retrospectively compared treatment outcomes and complications based on body mass index (BMI) in patients with renal stones treated with mini-endoscopic combined intrarenal surgery (ECIRS) using percutaneous tracts 20 Fr or smaller. Among 1,432 patients who had ECIRS performed at multiple registered facilities between January 2015 and December 2022, 870 patients with renal stones who underwent mini-ECIRS were included after excluding those with anatomical anomalies or incomplete clinical data. The patients were divided into two groups : BMI ≥30 (Group A) and BMI ＜30 (Group B). The treatment outcomes and complications were compared between the two groups. One month postoperatively, plain computed tomography (CT) and kidney ureter bladder radiography (KUB) were performed to assess stone fragmentation and hydronephrosis. According to postoperative imaging, stone-free was defined as residual fragments 4 mm or less on KUB and 2 mm or less on CT. Of the 870 patients, 86 were in Group A and 784 in Group B. The median (interquartile range) cumulative stone diameter was 33.8 (26.35-50.75) mm in Group A, and 32 (24-47) mm in Group B, respectively. The median operative time was 122.5 (92.25- 166.75) min in Group A and 114.5 (89.75-156) min in Group B. The mean and median (interquartile range) postoperative hospital stay were 5.9±2.5 days and 5 (4-7) days in Group A, and 5.4±3.3 days and 5 (4-6) days in Group B. Stone-free rates were 77.9% (67 cases) by KUB and 61.6% (53 cases) by CT in Group A, and 76.1% (597 cases) by KUB and 58.0% (455 cases) by CT in Group B. The incidence of postoperative fever (≥38.0°C) was 38.4% (33 cases) in Group A and 31.8% (249 cases) in Group B, while septic shock occurred in 2.3% (2 cases) of Group A and 2.6% (20 cases) of Group B. A statistically significant difference (p＜0.05) was found in the postoperative hospital stay between the two groups, but no significant differences were observed in the stone-free rates or complication rates. Mini-ECIRS using percutaneous tracts of 20Fr or smaller for renal stones showed no significant difference in SFR and complications between patients with a BMI ≥30 and those with a BMI ＜30.