Acute superior mesenteric artery occlusion

Dr Henry Knipe and Assoc Prof Frank Gaillard et al.

Acute superior mesenteric artery (SMA) occlusion, which can then result in acute mesenteric ischemia, 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 an increased risk of other cardiovascular events. 

Clinical presentation is variable and unfortunately often non-specific such that the diagnosis is not made for some time. It may be dramatic with acute onset severe abdominal pain or can be less well-defined 4,9.

Acute occlusion can be due to a number of causes 3,4,9:

  • embolic event: ~50% (range 40-60%)
  • acute in situ thrombosis superimposed on atherosclerosis: 15-30%
  • 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 ischemia
    • ventricular aneurysm
  • right-to-left shunt

Ultrasound is able to demonstrate normal flow in both the 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.

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.

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

Findings in acute SMA occlusion include 5,6,9:

  • arterial changes: lack of enhancement of the lumen of the SMA and/or its branches
    • embolism lodgement location varies
    • thrombosis usually occurs in the proximal 2 cm of the SMA
  • bowel changes: reflecting reduction/obliteration of blood supply
    • mucosal/serosal enhancement absent
    • 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
      • a thickened wall may also be present but does not correlate with severity
    • ileus / dilated loops of bowel: >3 cm in diameter
    • air-fluid or blood-fluid levels: due to dysfunctional peristalsis
    • necrotic mural gas may be present: pneumatosis intestinalis
  • other changes
    • mesenteric edema
    • free fluid
    • intrahepatic portal venous gas: due to pneumatosis intestinalis
    • free intra-abdominal gas
  • causes: e.g. intracardiac thrombus in a dilated left ventricle

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

An acute SMA 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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Cases and figures

  • SMA thromboemboli...
    Case 1: thromboembolism
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