Inflammatory bowel disease (IDB) is systemic disorder. An increased risk of arterial and venous thrombosis was originally reported by Borgen and Barker in 1936. Clinically, it is seen only 1-3% of patients admitted to the hospital for IBD. Ulcerative colitis may be complicated by macrovascular thrombosis. The most common manifestations are deep vein thrombosis of the leg and pulmonary emboli. Several mechanisms have been described which might explain an increased tendency for thromboembolic events in patients with IBD. Genetic risk factors for venous thrombosis are classified as deficiencies of protein C, protein S, antitrombin III, factor V leiden and protrombin 20210, hyperhomocysteinemia.