Anticoagulation therapy dramatically improved severe sigmoiditis with findings resembling inflammatory bowel disease, which was caused by mesenteric venous thrombosis.

Mesenteric venous thrombosis is an insidious disease, with a high mortality rate typically attributed to the long delay in diagnosis. Rapid diagnosis and treatment are important. Here, we present a patient with idiopathic inferior mesenteric venous (IMV) thrombosis. A 65-year-old man presented with constant abdominal pain associated with fever and bloody diarrhea. He was diagnosed with severe ulcerative colitis and was treated with mesalazine and prednisolone. The prednisolone was tapered because of liver dysfunction, and he received total parenteral nutrition for a month. His abdominal pain and bloody diarrhea worsened, and he lost 5 kg of weight. He was then transferred to our institute. Computed tomography showed thickening of the left colon. Colonoscopy showed diffuse colitis with multiple ulcers, large edematous folds, congested mucosa, and stenosis of the sigmoid colon, with sparing of the rectum, raising the possibility of IMV thrombosis. Angiography confirmed IMV thrombosis. Anticoagulation therapy was initiated with intravenous heparin followed by oral warfarin. His abdominal pain and diarrhea resolved, and he was discharged from hospital. Six months later, he remained asymptomatic with normal colonoscopic findings.