# Risk and protective factors for anastomotic insufficiency in elective colon and rectal cancer resections – a multivariate analysis with over 700 patients

## TL;DR

This study identifies risk and protective factors for anastomotic insufficiency in colorectal cancer surgery, finding that left-sided resections and obesity increase risk, while oral antibiotics reduce it.

## Contribution

The study confirms known risk factors and identifies oral antibiotics as a novel protective factor against anastomotic insufficiency in colorectal cancer surgery.

## Key findings

- Left-sided resections and obesity significantly increase the risk of anastomotic insufficiency.
- Preoperative oral antibiotics significantly reduce the risk of anastomotic insufficiency in both colon and rectal cancer surgeries.
- A single or double oral dose of antibiotics is safe and effective as a protective measure.

## Abstract

This study aimed to identify the risk factors and protective factors for AL.

Data from 717 patients with colorectal cancer with primary anastomosis who underwent elective surgery between 2012 and 2019 (418 patients with colon and 299 patients with rectal cancer) were extracted from prospectively established and retrospectively analyzed databases of two certified colorectal cancer centers, and processed for pre-, intra-, and postoperative risk factors in a multivariate analysis.

AL occurred in 33 (7.6%) patients with colon cancer and 30 (10%) patients with rectal cancer. AL was more likely after (extended) left hemicolectomy/sigmoidectomy (OR 3.771; 95% CI 1.17–12.154; p = 0.026) and in combination with perioperative administration of blood transfusions (OR 2.926; 95% CI 1.013–8.455; p = 0.047) in colon surgery. BMI ≥ 30 kg/m2 significantly increased the probability of AL (OR 7.136; 95% CI 2.248–12.651; p < 0.001) in rectal cancer surgery. Preoperative oral antibiotics, mainly in combination with mechanical bowel preparation, were associated with a reduced AL rate in both entities (OR 0.199, 95% CI 0.064–0.617; p = 0.005 for colon; OR 0.278, 95% CI 0.078–0.985; p = 0.047 for rectal cancer), regardless the antibiotic regimen used. The number required for treatment was calculated as 15.94.

Our study, reflecting daily clinical practice, confirmed known risk factors (left-sided resection, perioperative blood transfusions, obesity) and identified oral antibiotics as the only protective factor against AL. The application of a single or double oral dose of two antibiotics is safe and pragmatic and should be implemented in standard operative procedures for colorectal cancer surgery.

The online version contains supplementary material available at 10.1007/s00423-025-03953-9.