Atrial fibrillation is associated with an increased risk of lower gastrointestinal bleeding, primarily due to the use of anticoagulant therapy in these patients.
- Patients with atrial fibrillation often require anticoagulation therapy to reduce the risk of stroke, which increases the risk of gastrointestinal bleeding.[1-3] 
- The median rate of major bleeding for patients on vitamin K antagonists, commonly used for atrial fibrillation, is about 2.51 bleeds per 100 patient years, with the gastrointestinal tract being the most common bleeding site.[2] 
- The risk of gastrointestinal bleeding is further elevated in patients with atrial fibrillation who are older or have other comorbid conditions such as liver disease or thrombocytopenia.[2] 
- In a study, lower gastrointestinal bleeding in anticoagulated patients with atrial fibrillation showed a significant association with the subsequent diagnosis of colorectal cancer, indicating that such bleeding might unmask an underlying condition like colorectal cancer.[4] 
- The HAS-BLED score is used to assess the risk of bleeding in patients with atrial fibrillation to guide the clinical decision on starting anticoagulation therapy.[3]