Is Smoking a Risk Factor for Anastomotic Leak?
Yes, smoking is definitively a significant and modifiable risk factor for anastomotic leak after gastrointestinal surgery, and patients should stop smoking at least 4 weeks before elective surgery. 1
Strength of Evidence
The evidence supporting smoking as a risk factor is robust:
High-quality evidence from the Enhanced Recovery After Surgery (ERAS) Society guidelines establishes that current smokers have an increased risk for postoperative pulmonary and wound complications, with a strong recommendation that smoking cessation of at least 4 weeks is required to reduce complication incidence 1
The British Society of Gastroenterology provides a strong recommendation that all patients smoking after intestinal resection for Crohn's disease should be actively encouraged to stop, based on moderate-quality evidence 1
Magnitude of Risk
The clinical impact of smoking on anastomotic leak is substantial:
Smokers have over 4 times greater risk of anastomotic leak compared to non-smokers (OR 4.2,95% CI 1.3-13.5, p=0.02) after left colectomy, with leak rates of 17% in smokers versus 5% in non-smokers 2
Smoking was identified as an independent risk factor for gastrointestinal anastomotic leak after cytoreductive surgery with HIPEC (OR 6.223, CI 2.814-13.760, p<0.001) 3
Current smokers had a 9.3% anastomotic leak rate in rectal surgery, significantly higher than the 3.3% rate in non-smokers 4
Critical Timing Consideration: Duration of Smoking Cessation
Simply quitting smoking shortly before surgery is insufficient:
At least 10 years of smoking cessation is required to normalize anastomotic leak risk to that of non-smokers in rectal cancer patients 4
Former smokers who quit for less than 10 years had a 12.9% leak rate, significantly higher than the 4.5% rate in those who quit for ≥10 years (OR 2.725, p=0.029) 4
The ERAS guidelines recommend a minimum of 4 weeks preoperative smoking cessation to reduce complications, though this represents the absolute minimum threshold 1
Clinical Implications
For elective surgery:
- Delay elective left colectomy and other gastrointestinal procedures until smoking cessation is achieved, ideally for at least 4 weeks 1, 2
- Counsel patients that recent smoking cessation (less than 10 years) still confers elevated risk compared to long-term non-smokers 4
For urgent/emergent surgery:
- Recognize that active smoking status increases baseline risk and may influence decisions regarding protective measures (such as diverting stoma consideration) 5
- Intensify postoperative monitoring in smokers given their elevated leak risk 4, 2
Common Pitfall to Avoid
Do not assume that brief preoperative smoking cessation (days to weeks) eliminates the increased risk. While 4 weeks is the minimum recommended cessation period to reduce complications 1, optimal risk reduction requires substantially longer cessation periods, potentially up to 10 years for complete normalization of anastomotic leak risk 4. For patients who cannot achieve prolonged cessation before necessary surgery, acknowledge the elevated baseline risk and consider risk-mitigation strategies accordingly.