Acute Superior Mesentric artery Occlusion

Clinical History

87-year-old patient with known atrial fibrillation treated with warfarin complaining of sudden onset of severe abdominal pain associated with repeated vomiting, generalised abdominal tenderness. White Blood Count 14, lactate 3.5

Imaging Findings

A large filling defect was seen in the superior mesenteric artery (SMA) at the level of L2 vertebral body. This confirmed SMA thrombus which was almost occluding the vessel. There was still minimal contrast seen in the distal SMA branches.
Loops of fluid filled small bowel with poor wall enhancement were also noted. No findings of transmural gas or mucosal oedema appreciated.

Discussion

Superior Mesentric artery (SMA) is a branch of abdominal aorta. Arterial branches from SMA supplies blood from the lower part of the duodenum to 2/3rd of the transverse colon including the pancreas.

SMA obstruction is an acute abdominal conditions and has the highest mortality among all causes of acute abdominal pain, with mortality rate ranging from 83% to 93% [1].
The risk factors for the arterial thrombosis are atrial fibrillation, atherosclerosis, cardiac failure, recent myocardial infarction, intraabdominal malignancy. Women are more commonly affected than men and the elderly are especially susceptible.

Occlusion of SMA can occur from either an embolic episode or a thrombotic event. SMA is one of the common branches which become thrombosed. This acute vessel occlusion stops blood flow to the gut and eventually leads to necrosis causing bowel perforation and sepsis. If this condition is not treated quickly and efficiently it can lead to death.

Patients with this condition presents with acute onset of generalised abdominal pain notably 15-20 mins after eating and can last more than an hour. Vomiting is usually present. Patients can also complain of rectal bleeding.
Accurate biochemical markers are currently not available. High white blood count and increased lactate are often noted.
Plain abdominal X-ray usually shows distended small bowel, thickened bowel wall, and air fluid levels. Late findings include intramural air, air in the portal venous system and if bowel perforation occurs, free air in the abdomen is observed. Plain film provides a presumptive diagnosis in 20%-30% of the patients.

Computed tomography (CT) examination with contrast administration is one of the most specific investigations, findings with specificity greater than 95%. CT findings often show SMA occlusion, poor bowel wall enhancement, intestinal pneumatosis, portal venous gas, and ischaemia of other organs [2]. With advances in computed axial tomography, contrast-enhanced multidetector computed axial tomography (MDCAT) facilitates faster evaluation of patients with acute abdomen using high resolution reconstructed images.

Bipolar Angiography is considered the gold standard investigation in diagnosis as it accurately shows the presence and extent of occlusive disease. Collateral pathways are visualised in anteroposterior views, while lateral projections show the origins of visceral branches.

Exploratory laprotomy, resection of the dead bowel with or without anastomosis and endarterectomy of the affected artery is often indicated. In centres with endovascular expertise, endovascular therapy with or without open surgery has also been highlighted in recent literature, as one of the procedures for the above condition with good results.

Differential Diagnosis List

Final Diagnosis

Superior Mesentric Thrombosis resulting in Small Bowel Ischaemia

URL:	https://www.eurorad.org/case/10411
DOI:	10.1594/EURORAD/CASE.10411
ISSN:	1563-4086