Updated: 5/19/2017

Superior Mesenteric Artery Syndrome

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Overview
 

 
Snapshot
  • A 39-year-old woman presents with two weeks of nausea, epigastric pain after eating, and weight loss. These symptoms have progressively worsened and are relieved with lying in the prone or left lateral decubitus position. Medical history is significant for poorly controlled HIV secondary to medication non-adherence. On physical exam, the patient appears underweight with a current weight of 90 lbs (40.8 kg) which decreased from her previous weight of 140 lbs (63.5 kg). An abdominal radiograph is obtained which shows dilatation of the proximal duodenum. An upper gastrointestinal series is performed which also shows proximal duodenal dilatation with delayed passage of contrast.
Introduction
  • Definition
    • duodenal compression secondary to a decrease in the angle between the superior mesenteric artery (SMA) and aorta
  • Epidemiology
    • incidence
      • ~ 0.01-0.8% in the US based on upper gastrointestinal tract barium studies
    • demographics
      • more common in females
      • 10-39 years of age
    • location
      • the third portion of the duodenum becomes compressed
    • risk factors
      • severe weight loss leading to a decrease in mesenteric and retroperitoneal fat
        • cancer
        • malabsorption
        • HIV infection
        • scoliosis surgery
  • Pathophysiology
    • pathoantomy
      • the third portion of the duodenum courses between the SMA and aorta
        • the SMA is enveloped by lymphatic and fat tissue
          • normally, the angle between the SMA and aorta is approximately between 40-60°
            • mesenteric fat pad contributes to this angle
              • loss of mesenteric fat pad results in compression of the distal duodenum
  • Prognosis
    • prognostic variable
      • favorable response to conservative treatment when patients presents with <1 month of symptoms
Presentation
  • Symptoms
    • nausea
    • vomiting
    • weight loss
    • postprandial epigastric pain
    • bilious emesis (in severe obstruction)
  • Physical exam
    • nonspecific findings
    • weight loss
Imaging
  • Plain abdominal film
    • may show signs of small bowel obstruction
      • e.g., gastric distension and dilation of the proximal duodenum
  • Upper gastrointestinal series 
    • delay of contrast passage into distal small bowel
    • prolonged retention of barium in the proximal portion of duodenum and stomach
  • Ultrasonography
    • can be used to measure aortomesenteric angle and distance
  • CT or MRI angiography (contrast enhanced)
    • can be used in unclear cases
    • can measure aortomesenteric angle
Differential
  • Gastroesophageal reflux disease (GERD)
  • Small bowel obstruction
Treatment
  • Conservative
    • indications
      • this is considered first-line treatment for SMA syndrome and involves
        • fluid and electrolyte correction
        • duodenal and gastric decompression
          • via nasogastric tube
        • body positioning
          • prone or left lateral decubitus position which
            • eases pressure on duodenum
        • nutritional support
          • hyperalimentation for weight gain
  • Operative
    • duodenojejunostomy or Strong's procedure
      • indications
        • in cases refractory to conservative management
Complications
  • Complications
    • proximal duodenum dilatation
    • gastric reflux
      • may be accompanied by biliary emesis
 

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