Related Experiment Video
Updated: Oct 14, 2025

Tail Vein Transection Bleeding Model in Fully Anesthetized Hemophilia A Mice
Published on: September 30, 2021
Causes of gastrointestinal bleeding in oral anticoagulant users compared to non-users in a population-based study
Arnar S Ágústsson1,2, Arnar B Ingason1,2, Edward Rumba1,2
1Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
Background/Aims:
Causes of gastrointestinal bleeding (GIB) in patients on oral anticoagulants (OACs) are not well established. The aims of the study were to compare the causes of GIB in patients on OACs and those not on OAC therapy.
Methods:
A nationwide study of all GIB events in patients on OACs in Iceland from 2014-2019 was conducted. Bleeding events were obtained through ICD-10 codes and review of endoscopy databases, confirmed by review of medical records. For comparison, patients not on OACs from previous Icelandic population-based studies were used.
Results:
Among 752 GIB events in 12,005 patients on OACs, 273 (1.9%) had verified upper and 391 (2.7%) had verified lower GIB. For lower GIB, multivariate analysis showed that OAC users were more likely to have colonic polyps (OR 6.6, 95% CI: 2.4 - 17.8, p < .001) or colorectal cancer (OR 3.7, 95% CI: 2.0 - 7.0, p < .001) but less likely to have ischemic colitis (OR 0.11, 95% CI: 0.04 - 0.26, p < .001). For upper GIB, bleeding from mucosal erosions (OR 4.0 95% CI: 2.5 - 7.9, p < .001) and angiodysplasia (OR 3.6, 95%CI: 1.5 - 8.6, p = .003) were more common in OAC users.
Conclusions:
A high proportion of GIB caused by colonic polyps and colorectal cancer among OAC patients indicates that OACs treatment may facilitate cancer diagnosis. The low proportion of ischemic colitis among those on OACs suggests that OACs provide a protective effect against ischemic colitis. OACs seem to increase the bleeding from angiodysplasia and mucosal erosive disease.
Related Concept Videos
Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
Anticoagulant Drugs: Low-Molecular-Weight Heparins
Disorders of Hemostasis
Thromboembolic Disorders
Two factors primarily cause thromboembolic conditions.
Peptic Ulcer Disease I: Introduction
An acute ulcer, marked by superficial erosion and minimal inflammation, swiftly resolves upon identifying and addressing the underlying cause. In contrast, a chronic ulcer persists, potentially eroding through the muscular wall and forming fibrous tissue.
Peptic ulcers can also be...
Venous Thrombosis III: Interprofessional Care
Esophageal Varices-II: Clinical Features and Management
In the initial assessment, a thorough review of the patient's medical history is vital to identify risk factors such as liver disease, alcohol...

