The impact of body mass index on colorectal surgery: A short‐term outcome and cost analysis in an Asian cohort of 3169 patients

Abstract Background Extremes of body weight may be associated with poorer outcomes after colorectal surgery (CRS). We aimed to compare perioperative results and healthcare costs across the full range of body mass index (BMI) categories in an Asian cohort following CRS. Materials and Methods This retrospective study was conducted using the American College of Surgeons – National Surgical Quality Improvement Programme (ACS‐NSQIP) Participant Use Data File to identify patients ≥18 years old who underwent major elective CRS between January 2018 and December 2023. Both malignant and benign surgical indications were included. Emergency surgery was excluded. BMI was classified according to WHO Asian categories. Results Over 72 months, 3169 patients (53.3% male), with a median age of 68.4 years, underwent elective CRS (83.4% for colorectal cancer). The median overall BMI was 23.2 (IQR 20.5–26.3) kg/m 2 with 351 (11.1%) underweight, 1168 (36.8%) normal weight, 566 (17.9%) overweight, 819 (25.8%) obesity class I and 265 (8.4%) obesity class II. Underweight BMI was independently associated with increased 30‐day mortality (OR 2.54, 95% CI 1.01–6.41) and pneumonia (OR 1.89, 95% CI 1.03–3.40), while overweight BMI was independently associated with increased deep incisional surgical site infection (OR 3.31, 95% CI 1.18–9.97). The underweight group incurred the highest mean total cost per patient at $28,557.35, which was $4624.17 higher compared to the overall mean ( p = 0.001). Conclusion Underweight BMI is independently associated with increased risks of early mortality and pneumonia following CRS in an Asian population, with greater healthcare costs incurred compared to patients in higher BMI categories.