1546 Idiopathic Myointimal Hyperplasia of Mesenteric Veins: A Rare Cause of Treatment Refractory Colitis

Abstract

INTRODUCTION: Idiopathic myointimal hyperplasia of mesenteric veins (IMHMV) is a rare disease which mimics inflammatory bowel disease (IBD) clinically and endoscopically while showing ischemic changes without classic features of IBD on pathology. Delay in diagnosis is common; definitive diagnosis is usually only feasible after surgical resection. CASE DESCRIPTION/METHODS: A 62-year-old male with a past medical history of hypertension and hyperlipidemia presented with a 1-year history of recurrent abdominal pain, bloody diarrhea, and rectal pain. He was initially evaluated at another hospital and diagnosed with pneumatosis intestinalis and left-sided colitis. Left colon biopsies were suggestive of ischemia but computerized tomography angiogram (CTA) revealed patent mesenteric arteries. Extensive workup for thrombophilia, infectious, inflammatory, and autoimmune etiologies were negative. His symptoms did not respond to antibiotics and oral steroids. He presented to our institution for a second opinion. At presentation, he was diaphoretic, afebrile and in distress. Physical exam was significant for lower abdominal tenderness without peritoneal signs. Laboratory investigations revealed elevated inflammatory markers (Table 1). Repeat CTA showed patent mesenteric arteries. Colonoscopy revealed severe inflammation and congestion extending from the mid-transverse colon to the rectum. The terminal ileum and ascending colon were normal. Biopsies from inflamed mucosa revealed ischemic colitis with fibrinoid microvascular wall necrosis and fibrin thrombi (Figure 1). He was started on IV Methylprednisolone 40 mg daily but symptoms progressed despite IV steroids. He underwent total colectomy with end ileostomy which was curative. Histopathological analysis of the resected colon confirmed IMHMV. DISCUSSION: Current opinion suggests that IMHMV is caused by non-inflammatory, non-thrombotic obliteration of medium-to-large size mesenteric veins. IMHMV is a difficult diagnosis to make preoperatively. However, preoperative diagnosis is suggested by the presence of arterialized capillaries, subendothelial fibrin deposits and fibrin thrombi on endoscopic biopsies. IMHMV is typically refractory to steroids and biologics. Gastroenterologists and pathologists should have a high index of suspicion for IMHMV in patients with treatment refractory colitis, negative mesenteric angiography and colon biopsies showing ischemic changes without classic features of IBD. Colectomy is usually curative without recurrence of symptoms.