1Tae Yang Kim,1Tariq Ali

1Norfolk & Norwich University Hospital

Background(s):

Since the first description of segmental arterial mediolysis (SAM) in 1976 by Slavin and Gonzales-Vitale, cases have been reported in the literature in increasing numbers and there is a growing awareness of this pathologic entity. Although the gold standard for diagnosis is histopathological, SAM is increasingly being described based on radiological appearances as the majority of suspected SAM cases do not go on to have a biopsy or surgical resection. There does not currently exist a consensus of non-histopathological diagnostic criteria for SAM, however many have adopted those described by Kalva et al in which imaging criteria include the presence of dissection, fusiform aneurysm, occlusion, beaded appearance, or wall thickening of the mesenteric or renal arteries, with the absence of associated contiguous aortic dissection or atherosclerosis; in the majority of studies the presence of dissection and aneurysm were the most common imaging findings and the diagnostic likelihood is increased when these are found in multiplicity rather than in isolation. The diagnosis of SAM is suspected where alternative pathologies are excluded or less likely, including congenital connective tissue disorders, collagen vascular disorders, inflammatory arteritis and fibromuscular dysplasia (FMD). There is particular debate in distinguishing SAM from FMD and whether or not they are truly distinct disease entities.

Material(s) and Method(s):

Cases of suspected SAM based on radiological findings were compiled at a single institution (NNUH) over a period of 7 consecutive years (2015 – 2021). All cases were reviewed by 3 interventional radiologists and representative cases were selected for presentation.

Result(s):

Eight cases of suspected SAM were selected in total. Four cases were detected following an acute presentation with symptoms including abdominal pain, vomiting, and signs of hypovolaemic shock associated with a low haemoglobin level. Four cases were detected incidentally on imaging performed to detect other pathologies, including CT colonography for change in bowel habit, US urinary tract for non-visible haematuria, and CT angiograms to detect abdominal aortic aneurysms (AAA) as part of the UK National AAA Screening Programme. Affected vessels included branches of the coeliac artery, superior mesenteric artery and renal arteries, as well as iliac arteries. Pathologies included ruptured aneurysms, fusiform aneurysms, thrombosed aneurysms, beaded appearances due to multiple aneurysms and stenoses, and dissections. Endovascular treatment was by embolisation in all cases, predominantly with the use of coils. All cases of embolisation were successful.

Conclusion(s):

SAM can manifest itself acutely following a ruptured aneurysm, where it is a potentially life-threatening condition. SAM can also be detected incidentally with the increasing use of imaging for various clinical scenarios. SAM predominantly affects the mesenteric arteries, but is not limited to these vessels. Our case series are in concordance with the majority of other studies on SAM, whereby the most common imaging findings are the presence of aneurysms and dissections. Endovascular treatment with embolisation plays an important role in the management of SAM.