Case Presentation: 46-year-old male presented with sudden onset epigastric abdominal pain for 8 days at an outside hospital. He described pain as 6/10 intensity, dull in character, radiating in a band like pattern across the abdomen. Review of system was otherwise negative. CT scan of abdomen was done which showed no acute findings and was sent home with plan for EGD, but was later called back upon review of the CT scan which was concerning for inflammatory changes. CT angiogram was done showing inflammatory changes surrounding the celiac artery with extension into the splenic and common hepatic arteries with a short segment focal dissection measuring approximately 7 mm, with an associated pseudoaneurysm in the proximal aspect of the celiac artery. Due to concern for vasculitis, he was treated with pulse dose of methylprednisolone and was transferred to our center for rheumatological evaluation. On presentation to our center, patient’s abdominal pain had resolved, with normal ESR and CRP, ANA 1: 160, with homogenous pattern, normal complement levels, negative ANCA and hepatitis panel. Outside hospital CT images were reviewed at our center showed similar findings. Vascular surgery was consulted, and monitoring was recommended along with BP control. Repeat CT angiogram of abdomen/pelvis 5 days later re-demonstrated similar findings as above with stability of the pseudoaneurysm, with no evidence of bowel ischemia as the prior exam. Although single organ vasculitis versus polyarteritis nodosa were in the differential, the imaging findings (particularly the dissection) and the clinical picture was more suggestive of Segmental Arterial Mediolysis (SAM). Given this, further immunosuppression was held, and the patient was discharged with instructions to follow up as outpatient for evaluating the stability of the pseudoaneurysm and dissection.

Discussion: SAM is a non-inflammatory, non-atherosclerotic vasculopathy with a propensity to involve splanchnic vessels, but can also affect carotid, renal and intracranial vessels. Depending on the involved artery and underlying pathology (dissection with stenosis versus rupture), patients may present with sudden onset abdominal pain , chronic abdominal pain or even hemorrhagic shock. Characteristic CT angiography features are fusiform aneurysms and stenosis sometimes in series, dissections, and occlusions within the splanchnic arteries, this is important to be known as specimen for pathology is often times is not possible. Atherosclerosis, fibromuscular dysplasia, various forms of systemic vasculitis should be considered in the differential diagnosis. Laboratory screening tests, including acute phase reactants, specific autoantibodies and CT angiography showing characteristic pattern can be helpful in differentiating the diagnosis. No formal guidelines exist for the management of SAM, and hence to be aware of this possible diagnosis is important for preventing unnecessary immunosuppression.

Conclusions: Due to lack of specific diagnostic criteria, we write this report to highlight that internal medicine physicians should be aware of this vasculitis mimicker and do appropriate laboratory tests, CT angiography and digital subtraction angiography if needed, along with consult to rheumatology to prevent unnecessary immunosuppression for the benefit of the patients. Furthermore, patients with aneurysm should be followed up for assessing its stability, and prompt treatment in case of enlarging aneurysms to prevent hemorrhagic shock.