Segmental Arterial Mediolysis and Other Mimics of Medium Vessel Vasculitis: A Case and Review

Background: Segmental arterial mediolysis (SAM) is a non-inflammatory vasculopathy that primarily affects the abdominal visceral arteries leading to hemorrhage, ischemia, or pseudoaneurysms. Its presentation can be mimicked by other vasculopathies including vasculitis involving the medium-sized blood vessels making it difficult to diagnose. Case Presentation: A 55-year-old woman presented with a two-hour history of sudden-onset, severe epigastric pain radiating to the chest. She was noted to be hypotensive with low hemoglobin 8.8 g/dL suspicious for a hemorrhagic cause. Her case was complicated by elevated international normalized ratio 3.7 in the setting of warfarin therapy for the mechanical mitral valve. The remainder of her complete blood count, complete metabolic panel, inflammatory markers, autoantibody serologies, and infectious testing were negative. Abdominal computed tomography angiogram revealed hemoperitoneum, bilateral renal infarctions, a large mesenteric hematoma, aneurysmal disease of the common hepatic and inferior mesenteric arteries, thrombosis and proximal dissection of the superior mesenteric artery, acute thrombosis of the left external iliac vein, and multiple sites of arterial extravasation from the pancreaticoduodenal artery and its branches. Mesenteric artery angiogram showed multivessel visceral artery aneurysms and stenoses characteristic of SAM for which she underwent transcatheter arterial embolization of the bleeding vascular bed. We provide a narrative literature review with a focus on common presentations and differentiating characteristics of vasculopathies that can involve medium-sized blood vessels. It is important to accurately diagnose SAM and its potential mimics as management strategies differ. Conclusions: SAM presents with medium vessel vasculopathy without vasculitis. Differentiation from mimics can be difficult but aided by familiarity of their characteristic findings and differentiating clinical characteristics.