S36 Idiopathic Myointimal Hyperplasia of the Mesenteric Veins a Rare Mimic of Inflammatory Bowel Disease: A Systematic Review

Background: Idiopathic myointimal hyperplasia of the mesenteric veins (IMHMV) is an extremely rare non-thrombotic mesenteric veno-occlusive disease. IMHMV manifests with non-specific symptoms mimicking inflammatory bowel disease. Therefore, patients are initially misdiagnosed with and treated for acute severe ulcerative colitis. However, given its rarity, the optimal surgical intervention remain undefined. Hence, this study aimed to perform a systematic review to assess the various surgical procedures and associated outcomes for patients with IMHMV. Methods: We conducted a systematic search for articles reporting patients with IMHMV in MEDLINE, EMBASE, Cinahl, Scopus, Web of Science, and Cochrane Library. The search was conducted from 1946 to April 2022. We also retrospectively analyzed IMHMV cases managed at our institution until April 2022. The risk of bias of included studies was evaluated with a modified tool proposed by Murad et al A narrative synthesis of included studies was provided. Results: The search strategy retrieved 703 references, of which 54 studies were included. Fifty were case reports and 4 were case series. A total of 88 patients with IMHMV were included. Most patients (82%) were male, with a mean age of 56.6 years old (range: 13–83 years). The median follow-up was 24 months (range: 1 – 144 months) with surveillance performed primarily via endoscopic evaluation. Abdominal pain and diarrhea were the most frequent presenting symptoms. Most reports described involvement of the rectum and sigmoid colon (81%). Only 6 (8%) IMHMV cases were suspected preoperatively and underwent elective surgery. The majority (99%) of patients initially managed medically eventually required surgery. Only 1 patient sustained symptomatic resolution with medical management. The most common surgical procedures were Hartmann’s procedure (24%) and segmental colectomy (19%). Secondary anastomoses were reported in 10 cases and performed after endoscopic confirmation absence of disease between 2 – 10 months. A total of 3 (3%) patients underwent either total proctocolectomy or total abdominal colectomy/completion proctectomy with IPAA formation. Four (5%) complications were reported and these were noted to occur when the involved portion of the bowel was the ileum, ascending colon, or transverse colon. Nearly all (99%) patients achieved IMHMV resolution with primary surgical intervention. Only 1 (1%) patient required a completion total colectomy following IMHMV recurrence. The overall risk of bias was judged to be low in 4 studies, unclear in 19 studies, and high in 31 studies. Conclusion(s): IMHMV is a rare pathology typically diagnosed following surgical resection with only a few cases suspected preoperatively. Patients are oftentimes initially misdiagnosed with acute severe ulcerative colitis, because of the similarities in clinical manifestations. IMHMV is typically treated medically but surgical resection is nearly always needed due to failure of medical therapy. Surgical resection via Hartmann’s procedure or segmental colectomy have been shown to be safe and effective with a low risk of complications and recurrence. As a rare disease, more evidence is required to optimally inform surgical decision-making, but it appears that sparing the unaffected colon is reasonable. The creation of a national or global collaborative database would be useful to help optimize recommendations for patients with this rare disease.