Pre-Operative Risk for Colorectal Anastomotic Leakage: A Narrative Literature Review of Modifiable Risk Factors

Document Type : Narrative Review


1 FluidAI Medical (formerly NERv Technology Inc.), Kitchener, ON, Canada.

2 University of Toronto, Faculty of Medicine, Toronto, ON, Canada.



Anastomotic leaks (ALs) are a significant and feared postoperative complication, with an incidence of up to 30% despite
advances in surgical techniques. With implications such as additional interventions, prolonged hospital stays, and hospital
readmission, ALs have important impacts for patients, healthcare providers, and healthcare systems. The Risk of colorectal
anastomotic leakage can vary by patient, depending on a variety of factors. The aim of this paper is to explore modifiable preoperative risk factors, providing a window into areas that can be targeted to reduce the likelihood of AL. A literature search and review was conducted using the following keywords: anastomosis, anastomotic leak, colorectal, and risk factors. Following this, further review was conducted using keywords for these factors (alcohol, smoking, obesity, medications, immunosuppression, nutrition, and hypoalbuminemia; American Society of Anesthesiologists (ASA) physical status classification; mechanical bowel preparation; antibiotics). The significance of different modifiable pre-operative risk factors in the development of colorectal anastomotic leaks varies. Most conclusively, smoking, alcohol consumption, malnutrition (as reflected by hypoalbuminemia), and high ASA scores have strong evidence supporting a role in leak risk. Factors such as obesity (high BMI), non-steroidal antiinflammatory use, immunosuppression, and mechanical bowel preparation had mixed evidence demonstrating impacts on leak risk. Colorectal anastomotic leakage remains a significant challenge in intestinal surgery, despite medical advancements. Awareness of modifiable pre-operative risk factors enables clinicians to address these factors proactively, minimizing the risk of leaks where possible. Additionally, knowing which patients are high-risk ahead of surgery enables more careful postoperative management.