Association between the preoperative geriatric nutritional risk index and 90-day complications after open radical cystectomy: a retrospective cohort study

Background/objectives Muscle-invasive bladder cancer requiring radical cystectomy is associated with substantial postoperative morbidity, particularly in elderly patients. This study evaluated the predictive capacity of the preoperative Geriatric Nutritional Risk Index (GNRI) for 90-day complications following open radical cystectomy with ileal conduit urinary diversion. Methods We conducted a single-center retrospective cohort study of 80 consecutive patients who underwent open radical cystectomy and exclusively ileal conduit urinary diversion (100.0%) between November 2022 and December 2025. Preoperative GNRI was calculated from serum albumin and body weight metrics. Multivariable analysis was conducted using a 3-covariate Firth's penalized logistic regression model. An empirical threshold (GNRI < 94.5) derived from ROC analysis was evaluated alongside continuous GNRI scores. Results The overall 90-day complication rate was 82.5% (66/80). Mean preoperative GNRI was 94.81 ± 7.24. The ROC-derived optimal cutoff for overall complications was GNRI < 94.5 (AUC = 0.628, Sensitivity: 71.2%, Specificity: 57.1%). While continuous GNRI was not an independent predictor of total complications in multivariable analysis (OR: 1.052 per 1-unit decrease, 95% CI: 0.948–1.168, p = 0.342), patients with GNRI < 94.5 exhibited significantly higher rates of specific severe morbidity subtypes, including infectious complications (67.7% vs. 34.7%, OR: 3.95, p = 0.004), gastrointestinal complications (74.2% vs. 36.7%, OR: 4.95, p = 0.001), and cardiovascular adverse events (25.8% vs. 4.1%, OR: 8.17, p = 0.005). Advanced pathological stage (≥pT3) remained the sole independent predictor of overall 90-day morbidity (OR: 4.187, p = 0.024). Conclusions Preoperative GNRI is not an independent predictor of overall 90-day post-cystectomy complications; however, lower GNRI values (<94.5) strongly correlate with organ-specific infectious, gastrointestinal, and cardiovascular morbidity. GNRI serves as a valuable, objective screening tool within Enhanced Recovery After Surgery (ERAS) pathways to trigger targeted perioperative prehabilitation and nutritional optimization.