Segmental arterial mediolysis

Segmental arterial mediolysis (SAM) is a rare disorder of the arteries characterized by the development of aneurysms, blood clots, narrowing of the arteries (stenoses), and blood collections (hematomas) in the affected distribution.^[1][2]

SAM most commonly affects the arteries supplying the intestines and abdominal organs.^{[citation needed]}

Signs and Symptoms

Varies depending on the location of the affected blood vessels.

Gastrointestinal System:^[3]

• Acute abdominal pain (most common)^[4]
• Flank pain
• Nausea
• Vomiting
• Diarrhea
• Bloody stools
• Back pain

Nervous System^[3]

• Headache
• Stroke

The most severe signs occur if an aneurysm ruptures potentially resulting in:^[4]

• Shock
• Loss of consciousness
• Bleeding into the abdominal cavity
• Bleeding into the brain

Mechanism

1. The middle layer of an artery, called the media, made of smooth muscle is damaged.^[3]
2. Mediolysis occurs when the smooth muscle cells in the area of damage are destroyed.^[3]
3. Small gaps are formed in the wall of the artery which then fill with blood.^[3]
4. Gaps create weakness in the wall of the artery, allowing increasing pressure from blood to expand the gaps resulting in an aneurysm.^[3]
5. Aneurysms have potential for rupture.^[3]

Diagnosis

Often Segmental Arterial Mediolysis is diagnosed after clinical presentation with symptoms as above followed by CT angiogram or MRI demonstrating aneurysm(s).^[4] The gold standard method for confirming the diagnosis is surgical resection of the affected area of blood vessel followed by histologic investigation under a microscope.^[3] Segmental Arterial Mediolysis must be differentiated from fibromuscular dysplasia, atherosclerosis, and other systemic vasculidites including polyarteritis nodosa, Takayasu's arteritis, Behcet's disease, cystic medial necrosis, and cystic adventitial artery disease.^[4]

Treatment

Patients presenting with bleeding into the abdominal cavity require possible blood transfusions and emergent intervention with coil embolization via catheter angiography.^[3] Patients without active bleeding, but diagnosed aneurysms should have strict blood pressure control with antihypertensive drugs to decrease the risk of aneurysm rupture.^[3]

Epidemiology

Since it was first reported in 1976^[5] there have been 101 documented cases of Segmental Arterial Mediolysis.^[6] Although typically seen in older patients with an average age of 57 years old,^[6] it can affect patients of any age and does not favor one gender or the other.^[5]