Association of Body Mass Index with Complications After Radical Cystectomy: A Systematic Review and Meta-Analysis

Background: Radical cystectomy (RC) has high postoperative morbidity. Body mass index (BMI) is a modifiable factor, but its association with complications after RC remains controversial. Some studies report higher risk in obese patients, while others find no association or even a protective effect ("obesity paradox"). We conducted this review to clarify the association between preoperative BMI and overall and severe complications after RC.

Methods: We searched PubMed, Web of Science, Cochrane Library, CNKI, Wanfang, and CQVIP from inception to January 20, 2026. We included cohort studies reporting BMI as categorical variables (normal, overweight, obese) or continuous variables with overall or severe postoperative complications (Clavien–Dindo ≥ III or equivalent). Quality was assessed using the Newcastle-Ottawa Scale. Risk ratios (RRs) for categorical comparisons and adjusted odds ratios (ORs) for dose-response analysis (per 1 kg/m² increase) were derived from random-effects models. Heterogeneity was assessed using I². Prediction intervals (PI) were calculated for comparisons with ≥5 studies.

Results: Nine studies (n=3974) were included in the categorical meta-analysis and five studies (n=5872) in the dose-response analysis. Obesity was associated with an increased risk of overall complications (RR=1.16, 95% confidence interval (CI): 1.03–1.32; I²=24.9%; 95% PI: 0.85–1.60) and severe complications (RR=1.43, 95% CI: 1.02–2.01; I²=30.1%; 95% PI: 0.83–2.46). No significant differences were observed between overweight and normal-weight patients for overall or severe complications, nor between obese and overweight patients. In the dose-response analysis, each 1 kg/m² increase in BMI was associated with a 4% increase in overall complication risk (OR = 1.04, 95% CI: 1.01–1.07; I² = 56.3%; P for heterogeneity = 0.057). The included studies were of moderate to high quality (NOS scores 6–8).

Conclusions: Obesity is associated with significantly increased risks of overall and severe complications after RC, with a linear dose-response relationship (4% per 1 kg/m²). No statistically significant differences were observed between overweight and normal-weight patients, nor between obese and overweight patients; importantly, these null findings should not be interpreted as equivalence. Clinically, preoperative weight optimization remains exploratory pending interventional confirmation, while overweight alone should not delay surgery. Given the observational evidence and BMI limitations, interpret these findings cautiously.