A Case of Superior Mesenteric Artery Syndrome in Perianal Crohnʼs Disease

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Superior Mesenteric Artery (SMA) syndrome is a rare condition caused by compression of the duodenum between the aorta and SMA due to loss of mesenteric and retroperitoneal fat. Among IBD patients, SMA syndrome occurs more commonly in patients with ulcerative colitis (UC) after ileal pouch anal anastomosis (IPAA). This is the first reported case of SMA syndrome in a patient with perianal Crohn's disease (CD). A 32 year old female with perianal CD and diverting loop sigmoid colostomy on infliximab presented with 1 month of progressive, colicky, postprandial abdominal pain, nausea, sitophobia, diarrhea, and a 7 lb weight loss leading to an episode of orthostatic syncope. Contrast enhanced computed tomography showed distension of the stomach and proximal duodenum, but no obstruction, bowel wall thickening, or intraabdominal abscess. Small bowel follow through showed delayed transit through the duodenum in the region of the SMA as well as small bowel dilation proximal to the region of the SMA consistent with SMA syndrome. Magnetic resonance enterography showed no evidence of active CD. Serum inflammatory markers were within normal limits. Alternative etiologies such as delayed motility from diabetes, hypothyroidism, and other metabolic neuropathies were ruled out, and she was diagnosed with SMA syndrome. Despite modest improvement of her nausea with scheduled metoclopramide, total parenteral nutrition was started for inadequate nutrition prior to hospital discharge. SMA syndrome in IBD patients is most commonly associated with IPAA, which is performed for refractory ulcerative colitis or for resection of IBD-associated colon cancer. One proposed mechanism for this phenomenon is surgery-induced stretching of the SMA, flattening it against the aorta to cause duodenal narrowing. This is the first reported case of SMA syndrome in perianal CD status post diverting loop sigmoid colostomy. Perianal CD is an uncommon variant of CD and phenotypically mimics limited UC. Although our patient's surgery did not involve significant bowel resection as in an IPAA, perhaps this phenotypic similarity and post-surgical anatomic changes predisposed her to increased risk of SMA syndrome. For IBD patients presenting with obstructive symptoms such as nausea, vomiting, sitophobia, and abdominal pain, clinicians must maintain a low threshold for considering SMA syndrome since treatment differs significantly from treatment of IBD exacerbation.Figure: CT abdomen and pelvis axial image showing compression of duodenum between the superior mesenteric artery (SMA) and aorta.Figure: CT abdomen and pelvis sagittal image showing acute angulation of the superior mesenteric artery (SMA) and the aorta.