Idiopathic Myointimal Hyperplasia Is a Distinct Cause of Chronic Colon Ischemia

Abstract

Introduction: Colon ischemia (CI) is typically an acute manifestation of altered colonic blood flow resulting in mucosal ischemia and resolves spontaneously within days. Some patients, however, may evolve into chronic segmental colitis. This is a controversial topic, given the varied definitions of this entity and lack of distinguishing histologic features. We sought to further examine the clinicopathologic features of chronic CI in an attempt to distinguish it from acute CI. Methods: Cases were identified from our electronic medical record between 1/1/94 and 8/15/15. Only cases having symptom chronicity (>1 month of abdominal symptoms) and persistent ischemic histology in patients 18-99 years of age were included for review. Histologic evaluation was performed by two gastrointestinal pathologists. Results: From 15 CI patients with clinical and histologic chronicity, 8 had unequivocal venous intimal hyperplasia characterized by thickened submucosal, mural and extramural veins which defines the rare condition known as idiopathic myointimal hyperplasia of mesenteric veins (IMHMV). The remaining 7 patients had non-specific histologic findings of ischemia. The median age at diagnosis for patients with IMHMV was 62.5 years (range 22-75) compared to 61.6 years (range 29-88) in those without. By sex, 2 of the IMHMV and 3 non-IMHMV patients were female. Vascular imaging in all IMHMV cases demonstrated mesenteric arterial and venous patency. Abdominal pain and diarrhea were the two most common presenting symptoms, occurring in 7 (87.5%) and 5 (62.5%) cases, respectively. The sigmoid colon was most commonly involved in 75% of IMHMV versus only 29% of non-IMHMV cases. Surgical resection was performed in 7 IMHMV patients as part of management for CI or suspected inflammatory bowel disease, resulting in symptomatic resolution. In retrospect, all 7 IMHMV patients with resection had characteristic changes in pre-resection biopsies, including thickened, tortuous mucosal venules and, in some cases, myointimal hyperplasia in superficial submucosal veins. Conclusion: The histologic changes of IMHMV are distinctive in colonic resections and are not detected by vascular imaging. Pre-operative diagnosis of IMHMV is possible from endoscopically obtained biopsies, which show a combination ischemic injury and altered mucosal venules. As segmental colon resection is curative of IMHMV, improved awareness of this entity is needed to avoid misdiagnosis and potentially harmful treatment such as immunosuppression.