SMA syndrome

Vascular compression of the duodenum

• Also known as Wilkie syndrome and cast syndrome

Epidemiology

• Rare

Risk factors

• Weight loss leading to reduction in mesenteric fat pad
• Supine immobilisation
• Scoliosis
• Placement of a body cast
• Associated with PUD
• Anorexia nervosa
• Seen after proctocolectomy and J-pouch anal anastomosis, resection of an AVF of the cervical cord, AAA repair, and orthopaedic procedures (usually spinal surgery)
• Possible family history

Pathophysiology

• Compression of D3 by the SMA as it passes over
• Normal angle between SMA and aorta is between 38 and 65 degrees, and aortomesenteric distance is usually 10-28mm
• These measurements correlate with BMI
• In SMA syndrome, the angle can be as low as 6 degrees, with aortomesenteric distance as low as 2mm

Presentation

• Consistent with proximal SBO
• Nausea and vomiting
• Abdominal distension
• Weight loss (usually occurs before the onset of symptoms, and contributes to the aetiology)
• Post-prandial epigastric pain - varies from intermittent to constant depending on the degree of obstruction

Differential diagnosis

• Chronic mesenteric ischaemia

Diagnosis

• Upper GI series - abrupt or near-total cessation of flow
• CT
  • Duodenal obstruction with an abrupt cut-off at D3
  • Aortomesenteric angle <=25 degrees, especially if the aortomesenteric angle is <=8mm
  • High fixation of duodenum by ligament of Treitz, abnormally low origin of SMA, or anomalies of SMA

Management

• Conservative management initially - often successful
  • Resuscitation
  • Nutritional support - NJT feeding with weight gain
• Surgery
  • Duodenojejunostomy
  • Gastrojejunostomy
  • Duodenal de-rotation (Strong procedure)
    • Divide ligament of Treitz so the duodenum lies to the right of SMA

Outcomes

• Not particularly good, regardless of approach
• One of the largest series of surgical patients had 16 patients followed for seven years; most with essentially unchanged symptoms