Case Presentation: We present the case of a 31-year-old female with a medical history of superior mesenteric artery syndrome status-post duodenojejunostomy, postural orthostatic tachycardia syndrome, and joint hypermobility who presented with acute-on-chronic abdominal pain and a two-week history of postprandial diarrhea. CT angiography of the abdomen and pelvis revealed severe proximal celiac artery stenosis with patent collateralization and no evidence of median arcuate ligament syndrome, aortic dissection, or aortic aneurysm. She was evaluated by vascular surgery and minimally invasive surgery, who decided against acute intervention. Further imaging with MRA of the chest, abdomen, and pelvis showed celiac axis occlusion with circumferential progressive enhancement surrounding the vessel, raising concern for vasculitis. PET-CT confirmed persistent circumferential celiac artery enhancement but showed no other foci of perivascular hypermetabolism. Despite high concern for vasculitis, her autoimmune, inflammatory, infectious, and antiphospholipid syndrome tests were all negative. After discussion with rheumatology and radiology, her clinical picture was deemed most consistent with segmental arterial mediolysis (SAM). Early presentation of fibromuscular dysplasia was considered, but there were no additional imaging findings to support this diagnosis. There was also concern for vascular Ehlers-Danlos or Marfan syndrome given her hypermobile joints and marfanoid features, but the provisional results of her rapid genome testing were negative. She was ultimately discharged on antiplatelet therapy to reduce her thrombotic risk, along with an adequate pain regimen and plans for routine imaging surveillance to monitor for new or progressive vascular pathology.
Discussion: Segmental arterial mediolysis (SAM) is a rare, nonatherosclerotic, noninflammatory arteriopathy characterized by lytic degeneration of the arterial media. It most commonly affects medium-sized abdominal arteries such as the celiac, mesenteric, and renal arteries. SAM has an estimated incidence of roughly 1 in 100,000 cases per year; however, this is likely an underestimation as it is frequently misdiagnosed as other, more familiar vascular conditions. The imaging findings associated with SAM often mimic those of vasculitis or fibromuscular dysplasia, but as this case demonstrates, laboratory and serologic studies can be pivotal in distinguishing SAM.
Conclusions: SAM should be considered in patients presenting with acute abdominal or flank pain with radiologic evidence of medium-sized arterial dissection, aneurysm, or occlusion—especially when laboratory and serologic studies for vasculitis are negative. While the American Heart Association recommends histopathologic confirmation for definitive diagnosis, this is often impractical in clinical settings, so diagnosis is frequently based on clinical and radiographic findings. SAM’s clinical presentation is highly variable, ranging from self-limited abdominal pain to life-threatening hemorrhagic shock, with a reported mortality rate of up to 50%. Management strategies vary accordingly, from conservative management with blood pressure control and imaging surveillance to urgent endovascular or surgical intervention in unstable patients. Given the marked variability in SAM’s presentation and prognosis, timely recognition of this condition is critical in preventing serious complications and achieving optimal patient outcomes.