Preoperative very low-energy diets for obese patients undergoing intra-abdominal colorectal surgery: a retrospective cohort study (RetroPREPARE).

Background: Very low-energy diets (VLEDs) prescribed prior to bariatric surgery have been associated with decreased operative time, technical difficulty, and postoperative morbidity. To date, limited data are available regarding the impact of VLEDs prior to colorectal surgery. We designed this study to determine whether preoperative VLEDs benefit patients with obesity undergoing colorectal surgery.

Methods: This is a single-center retrospective cohort study. Individuals undergoing elective colorectal surgery with a body mass index (BMI) of greater than 30 kg/m² from 2015 to 2022 were included. The exposure of interest was VLEDs for 2-4 weeks immediately prior to surgery. The control group consisted of patients prior to January 2018 who did not receive preoperative VLED. The primary outcome was 30 day postoperative morbidity. Multivariable logistic regression modeling was used to determine associations with 30 day postoperative morbidity.

Results: Overall, 190 patients were included, 89 patients received VLEDs (median age: 66 years; median BMI: 35.9 kg/m²; 48.3% female) and 101 patients did not receive VLEDs (median age: 68 years; median BMI: 32.1 kg/m²; 44.6% female). One-hundred four (54.7%) patients experienced 30 day postoperative morbidity. Multivariable regression analysis identified three variables associated with postoperative morbidity: VLEDs [odds ratio (OR) 0.22, 95% confidence intervals (CI) 0.08-0.61, P < 0.01], Charlson comorbidity index (OR 1.25, 95% CI 1.03-1.52, P = 0.02), and rectal dissections (OR 2.71, 95% CI 1.30-5.65, P < 0.01).

Conclusions: The use of a preoperative VLED was associated with a significant reduction in postoperative morbidity in patients with obesity prior to colorectal surgery. A high-quality randomized controlled trial is required to confirm these findings.