Acute superior mesenteric artery occlusion

Acute superior mesenteric artery occlusion, which can then result in an acute mesenteric ischaemia, can be a life-threatening event related to the artery supplying the majority of the small bowel and right side of the colon

An acute occlusion is an uncommon event that typically affects elderly patients, who are at increased risk of other cardiovascular events. 

Clinical presentation is variable and unfortunately often nonspecific such that the diagnosis is not made for some time. It may be dramatic with acute onset severe abdominal pain or may be less well-defined 4.

Acute occlusion can be due to a number of causes 3,4:

  • embolic event: ~60%
  • acute in situ thrombosis superimposed on atherosclerosis: 30%
  • aortic dissection with the involvement of the SMA origin
  • slow flow or idiopathic 

Risk factors, therefore, include:

  • advanced age
  • smoking
  • prothrombotic tendency
    • antiphospholipid antibodies, etc. 2
  • valvular/cardiac abnormalities
    • mechanical heart valve
    • atrial fibrillation
    • acute myocardial ischaemia
    • ventricular aneurysm
  • right-to-left shunt
CT

Computed tomography is widely accepted as the first-line imaging technique for evaluation 7 due to its speed, widespread availability and ability to diagnose alternative causes of acute abdominal pain.

Technique

For a discussion on CT technique, refer to the intestinal ischaemia article. 

Findings

Findings in acute superior mesenteric artery occlusion include:

  • lack of enhancement of the lumen of the SMA and/or its branches
    • embolism lodgement location varies
      • 15% at the origin of the superrio mesenteric artery
      • 50% immediately distal to the origin of the middle colic artery 5
  • bowel wall
    • thickness
      • variable
      • in pure arterial occlusion, the wall may be thinned (a.k.a. paper-thin wall) due to loss of intestinal muscular tone and absence of blood supply 6
      • a thickened wall may also be present but does not correlate with severity 6
    • enhancement absent
    • necrotic mural gas may be present: pneumatosis intestinalis
  • intrahepatic portal venous gas: due to pneumatosis intestinalis
  • mesenteric oedema
  • ileus
  • free fluid
  • free intra-abdominal gas
Ultrasound

Ultrasound is able to demonstrate normal flow in both SMA and SMV but is incapable of assessing side branches or the bowel wall. It has little role in the acute management of this condition.

Angiography

Once the gold standard for diagnosis, now reserved for patients who may benefit from endovascular intervention.

An acute superior mesenteric artery occlusion carries a mortality of 75-90% despite treatment 3,5. Treatment options include 4:

  • endovascular thrombectomy
  • intraluminal papaverine
  • surgical thrombectomy with resection of non-salvageable infarcted bowel
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Article information

rID: 7043
Synonyms or Alternate Spellings:
  • Acute SMA occlusion
  • Acute SMA thrombosis

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