- BACKGROUND AND AIMS: To assess the effect of warfarin anticoagulation therapy (AC) on the incidence of colon bleeding after elective colonoscopy with polypectomy and to identify independent predictors of post-polypectomy colon bleeding. METHODS: This was a retrospective cohort analysis. Patients interrupting warfarin AC therapy for polypectomy (AC group) were matched on age (+/- 3 years) with up to two patients who underwent polypectomy but were not receiving AC (non-AC group). Data were extracted from electronic medical, pharmacy and laboratory claims and records and manual medical chart review. Incidence rates of colon bleeding requiring hospitalization, other gastrointestinal bleeding, thrombosis and death in the 30 days post-polypectomy were compared between groups. Multivariate regression techniques were used to identify independent predictors of post-polypectomy colon bleeding. RESULTS: A total of 425 AC group patients were matched to 800 non-AC group patients. Post-polypectomy colon bleeding occurred more often in AC group patients (2.6% vs. 0.2%, P = 0.005). There were no differences in the rates of other outcomes (P > 0.05). Independent predictors of colon bleeding included AC group status [adjusted odds ratio (AOR) = 11.6; 95% confidence interval (CI) = 2.3-57.3], number of polyps removed (AOR = 1.2; 95% CI = 1.1-1.4) and male gender (AOR = 9.2, 95% CI = 1.1-74.9). CONCLUSIONS: The incidence of post-polypectomy colon bleeding was higher in patients receiving AC even although warfarin was interrupted for the procedure. Independent predictors of colon bleeding were identified as: receiving AC, removal of multiple polyps and male gender. Our findings suggest that additional methods to reduce the likelihood of post-polypectomy colon bleeding in AC patients should be investigated.