Clinical predictors of blood loss during mini-endoscopic combined intrarenal surgery

Purpose Mini-endoscopic combined intrarenal surgery (ECIRS) effectively treats renal and ureteral stones over percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS) alone. However, factors influencing bleeding remain poorly understood. To mitigate bleeding during mini-ECIRS, we aimed to identify the factors associated with severe bleeding. Methods Clinical data from consecutive patients who underwent mini-ECIRS for renal and/or ureteral stones between 2015 and 2021 at three high-volume centers in Japan were analyzed. The inclusion criterion was mini-ECIRS with the modified Valdivia position. The primary outcome was the percentage of serum hemoglobin drop on postoperative day 1. Severe bleeding was defined as a ≥ 20% drop in hemoglobin or need for blood transfusion. Logistic regression models were used to identify the predictors of severe bleeding. Results Among 1333 patients, the mean hemoglobin drop was 9.6 ± 7.4%, and the transfusion rate was 0.5%. Severe bleeding occurred in 13.1% of the cases. Patients with severe bleeding had significantly higher residual stone rates (P = 0.005) and longer operative time (P = 0.005) than those without severe bleeding. Septic shock and arteriovenous fistulas (AVF) were also more frequent in the severe bleeding group (P < 0.001). Multivariate analysis identified that male sex (odds ratio [OR]: 1.904, 95% confidence interval [CI]: 1.263–2.870, P = 0.002), body mass index > 25 (OR: 1.885, 95% CI: 1.192–2.982, P = 0.007), and older age (OR: 1.017, 95% CI: 1.000–1.033, P = 0.047) were independent preoperative predictors of severe bleeding. Preoperative nephrostomy placement showed a trend toward reduced bleeding risk. Conclusions Severe bleeding during mini-ECIRS was associated with poorer surgical outcomes, including higher residual stone rates and an increased risk of septic shock and AVF. Male sex, obesity, older age, and longer operative time were the independent predictors. Preoperative nephrostomy may help reduce bleeding risk, supporting its selective use in high-risk patients to improve safety and stone-free outcomes.