Learning Radiology xray montage

Superior Mesenteric Artery Syndrome

  • Compression of 3rd portion of duodenum between the aorta and superior mesenteric artery (SMA)
  • Females more affected than males
    • Most often in older children, adolescents
  • Some doubt the true existence of the syndrome
  • Pathophysiology
    • Narrowing of angle between SMA and aorta
      • SMA usually forms an angle of 45 degrees with the aorta
  • Etiologies
    • Prolonged bed rest in supine position (body cast, whole-body burns, surgery)
    • Substantial and, frequently, rapid weight loss
    • Anorexia nervosa or malnutrition
    • Loss of abdominal muscle tone (as in pregnancy)
    • May be congenital
    • Seen in those with asthenic build
    • Exaggerated lumbar lordosis
  • Clinical findings
    • Epigastric pain
    • Nausea
    • Repetitive vomiting
    • Abdominal cramping
    • Typically findings are worst in supine position and may be relived by changing to the prone or left lateral decubitus positions
    • Associated with a higher than normal incidence of peptic ulcer disease and hyperchlorhydria
  • Imaging findings
    • Usually requires upper GI or CT of abdomen for diagnosis
    • Megaduodenum
      • Pronounced dilatation of 1st and 2nd portion of duodenum and frequently stomach
      • Best seen in supine position
      • Compression of duodenum between aorta and SMA
  • Vertical linear compression defect in transverse portion of duodenum overlying spine
  • Abrupt change in caliber distal to compression defect
  • Treatment
    • Relief of compression by postural change into prone knee-elbow position
    • Weight gain
    • Surgery is indicated only when conservative treatment is not successful
      • Duodenojejunostomy is the most frequently used procedure



Superior Mesenteric Artery Syndrome. Axial CT scans of the upper abdomen show a dilated 2nd portion of the duodenum (D) just proximal to a narrowed segment of the 3rd portion of the duodenum (green arrow) compressed between the superior mesenteric artery (red arrow) and the aorta (black arrow)

Dahnert, 5th Edition

Avinash Shetty, MD and Ivor D Hill, MB, ChB, DCH, FCP, MD: eMedicine