A 71-year-old man was admitted to our institution complaining of abdominal pain and constipation. Barium enema examination revealed narrowing, cobble stoning, and longitudinal ulcerations in the sigmoid colon and upper rectum. Conventional colonoscopy, magnifying narrow-band imaging endoscopy, and magnifying chromoendoscopy revealed edematous mucosa, longitudinal ulcerations with luminal narrowing, and multiple pseudopolyps. The histologic examination of the biopsy specimens showed thick-walled (arterialized) capillaries and subendothelial fibrin deposits in the mucosa and submucosa. Based on a preoperative diagnosis of idiopathic myointimal hyperplasia of mesenteric veins (IMHMV), he underwent a laparoscopic resection of the sigmoid colon and upper rectum. The histologic examination of the resected specimens showed marked proliferation of venous walls with marked myointimal thickening and luminal occlusion from the submucosa to the mesentery throughout the entire resected tissue section. The final diagnosis was IMHMV.
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