S6242 Polyarteritis Nodosa, a Rare Cause of Abdominal Pain

Introduction: Medium Vessel Vasculitides, including polyarteritis nodosa (PAN), are uncommon diagnoses that in atypical cases can present with abdominal pain as the only symptom. Mesenteric arteritis leads to vascular narrowing and resultant mesenteric ischemia, which can lead to bowel infarction and be life threatening if recognition is delayed. Early diagnosis with appropriate management is critical in improving patient outcomes. This case highlights the diagnosis and treatment of a patient with mesenteric ischemia due to PAN. Case Description/Methods: A 43-year-old man with type 1 diabetes mellitus presented with several weeks of postprandial epigastric and right upper quadrant pain, with associated weight loss of 20 lbs over the last 3 months. He had no nausea, vomiting, melena, hematochezia, nonsteroidal anti-inflammatory drug use, alcohol or drug use. Initial vital signs were normal and physical exam was notable for diffuse abdominal tenderness with guarding. Contrasted abdominal computed tomography showed near occlusive thrombosis of several branches of the superior mesenteric artery (SMA). Dedicated computed tomography angiogram was obtained for further clarification and showed circumferential thickening of the SMA, inferior mesenteric artery and common hepatic artery with fat stranding and diffuse inflammatory changes concerning for vasculitis, but no occlusion. Gastroenterology was consulted to evaluate for other etiologies of abdominal pain and upper endoscopy was unremarkable. Rheumatology was consulted given suspicion for vasculitis and the patient underwent a positron emission tomography/computed tomography scan that showed fluorodeoxyglucose avid celiac, SMA, and proximal intrahepatic vessels, consistent with a diagnosis of PAN. He received intravenous methylprednisolone for 3 days and was started on cyclophosphamide for definitive management. Discussion: Vasculitis, while rare, should be considered in the differential diagnosis in cases of abdominal pain without a clear etiology. In cases of vasculitis affecting the mesenteric vasculature, post-prandial abdominal pain occurs due to inflammation causing arterial narrowing and resultant ischemic injury. PAN is a vasculitis that is typically seen in men aged 30-60, with imaging showing circumferential wall thickening with stenosis of medium visceral vessels without occlusion/embolus. PET scan is usually required for definitive diagnosis. Given the need for timely diagnosis and treatments to improve outcomes for patients with these rare vasculitides, gastroenterologists should remember to consider them when seeing patients with abdominal pain of unclear etiology.