Segmental arterial mediolysis

A 79-year-old man with a medical history of anaemia, heart failure and atrial fibrillation attended the emergency department, referring to acute epigastric pain and unintended weight loss. The blood test revealed a worsening of his anaemia, hypertransaminasemia and renal failure. He was hospitalised for further studies, and a CT was performed.

Contrast-enhanced CT showed a fusiform dilation of the celiac trunk, originated a centimetre distance from the ostium, without identifying a significant stenosis at the proximal level. An image suggestive of dissection was found at the proximal end (Figure 1). In addition, stenosis of the left renal artery origin was seen (Figure 2). There were no other relevant findings in the study. 3D vascular reconstructions were performed (Figure 3).

Segmental arterial mediolysis (SAM) is a rare arteriopathy without an inflammatory or atherosclerotic origin. It affects medium-sized vessels, typically the splanchnic and renal arteries in various combinations, as in our case, but can also affect intracranial ones [1–3,6]. The cause of SAM remains unknown, but it may be related to a recurrent vasoconstrictive process [1,3]. It consists on the lysis of the arterial tunica media, resulting in single or multiple aneurysms formation, as well as dissections, occlusions and stenosis [1,2,4].

SAM has a wide variety of clinical presentations, which range from asymptomatic (9%) to haemorrhagic shock and death, depending on the vascular territory affected and secondary complications [1,2]. Abdominal pain (62%), followed by haemorrhagic shock (32%), abdominal distension (13%), haematochezia (11%) and strokes (6%) are the main symptoms [1,6].

Its confirmation relies on histology. However, since biopsy is an invasive procedure, some clinical, laboratory and imaging criteria have been proposed for its diagnosis. These could be summarised in a compatible presentation and discarding collagenopathies, vasculitis, atherosclerosis or infections. Serological tests may demonstrate the absence of inflammatory markers such as ANA, ANCA or CRP. The increased amount of imaging tests requested for the diagnosis of abdominal pathology is raising the detection of MAS in asymptomatic patients [1].

CT angiography is the standard technique for diagnosis and follow-up. MRI and angiography are useful. Using maximum intensity projections (MIP) may help in assessing arterial wall irregularities with alternating perivascular inflammation, aneurysms and stenosis in a “string of pearls” pattern. The most characteristic image of MAS is the dissecting aneurysm, but arterial wall thickening and arterial occlusions can be present [1,3,4]. Organ infarction and other complications can accompany it.

Similar chronic vascular lesions can be found in fibromuscular dysplasia (FMD), posing a common pathophysiological stem, one perhaps being a progressive form of the other [5]. However, FMD frequently affects renal arteries in young females [5,6]. Other differential diagnosis may be considered, as described below.

Treatment depends on the clinical presentation of the patient. In case of haemodynamic instability, acute intraabdominal haemorrhage may be suspected, and inotropic support and emergency haemostasis techniques will be necessary [1]. Open repair surgery and endovascular embolization techniques are the main plausible options [4]. Angiography confirms imaging diagnosis and helps in guiding endovascular therapies [1].

As SAM is a self-limiting disease, asymptomatic patients or those with fewer clinical manifestations will receive conservative treatment [1]. Antihypertensive therapy is the main cornerstone of medical therapy [3].

Take home messages

SAM is a rare non-inflammatory vasculopathy that should be suspected in patients developing aneurysms, dissections or spontaneous visceral artery ruptures with an unknown origin in an appropriate context.

Imaging findings are key for the diagnosis along with the clinical presentation, as only patients with complications undergo surgery, and biopsies are an invasive procedure. Radiologists should be familiar with this entity.

All patient data have been completely anonymised throughout the entire manuscript and related files.