Researchers report a case of vascular alterations with inflammation and evidence of venous outflow tract due to idiopathic myointimal hyperplasia of the mesenteric veins (IMHMV) in the January issue of Gastroenterology.
Michiel Bronswijk et al describe a 67-year-old man with a history of obesity, type 2 diabetes, and hemochromatosis admitted to the hospital with slowly progressive pain in the lower abdomen and fluctuating loose stools. He had progressive tenderness in the left abdomen and high levels of C-reactive protein (ranging from 20 to 34 mg/L, when the upper limit of normal is 5 mg/L), without any signs of malabsorption. Stool samples did not reveal any bacterial or protozoan pathogens.
At another hospital, the patient had recently received a diagnosis of rectocolitis of an unclear cause, after colonoscopy showed narrowing of the colon lumen and edematous mucosae in the descending colon and sigmoid.
Bronswijk et al ordered an abdominal computed tomography (CT) scan, and another colonoscopy. These confirmed colitis with prominent edema, limited to the descending colon and sigmoid and proximal rectum. Biopsies showed edematous mucosa and capillary congestion.
The second CT scan revealed progressive wall thickening of the descending and sigmoid colon and proximal rectum, with increasing mesenteric inflammation. It also found that the patient was missing an inferior mesenteric vein and had left-sided tortuous mesenteric veins. The combination of the vascular defects, inflammation, and evidence for a venous outflow tract problem led Bronswijk et al to believe the patient had IMHMV.
IMHMV is a rare, nonthrombotic, veno-occlusive disease characterized by proliferation in the intima of small and medium-sized mesenteric veins, leading to protracted rectosigmoiditis. It is most commonly observed in older men. Although most cases are identified in patients who undergo surgery after medical therapy has failed, IMHMV can be detected earlier based on several findings—early detection would prevent unnecessary treatment and diagnostic procedures.
Features of IMHMV include progressive left-sided colorectal wall thickening or rectosigmoiditis, absence of the inferior mesenteric vein in radiographic images, signs of venous stasis, and a patent inferior mesenteric artery. Most patients can be treated with segmental surgical resection, without signs of recurrence.
This patient underwent surgery, which identified a rigid and fibrotic sigmoid mesocolon (see figure). Surgeons performed a left-sided hemicolectomy with a transversorectal anastomosis. In addition to subserosal fatty necrosis, microscopy of the resected tissue revealed mucosal veins with severely reduced lumen, due to extensive fibromyxoid intimal hyperplasia (see figure), confirming the diagnosis of IMHMV. The authors found no signs of vasculitis or thrombosis. After 2 years of follow-up, the patient had no signs of recurrence.
What causes IMHMV? Some researchers have proposed local trauma due to sigmoid hypermobility and thrombophilia associated with variants in coagulation factor V (F5, or factor V Leiden). However, this patient was found to carry a a c.665C>T polymorphism in the methylenetetrahydrofolate reductase gene (MTHFR). So, thrombophilia and subsequent recurrent mesenteric thrombosis could increase risk of IMHMV.