SMA syndrome

Background

• Full name: Superior Mesenteric Artery Syndrome
• Rare condition
• Occurs when the duodenum is compressed between the aorta and the superior mesenteric artery
• Can lead to partial or complete gastrointestinal obstruction at the level of the duodenum

Etiology

• SMA branches from the abdominal aorta surrounded by fatty and lymphatic tissue known as the mesenteric pad
• SMA forms an angle of about 38 º and 65º with the abdominal aorta
• Third part of the duodenum courses between the angle formed by the SMA and aorta
• Any factor that sharply narrows the angle can cause entrap and compress of the duodenum
  • Factors that narrow this angle include:
    • Significant weight loss, most common factor
    • Corrective spinal surgery for scoliosis
    • Congenital defects, suggested genetic predisposition
    • Adhesions

Clinical Features

• Early satiety
• Nausea and vomiting, can be bilious
• Abdominal pain, mid-abdomen which may be improved with changes of position
• Abdominal bloating, especially after meals
• Bleching
• Weight loss
• Proximal small bowel obstruction

Differential Diagnosis

• See Abdominal Pain
• See Nausea and vomiting

Evaluation

• Suspected based on signs and symptoms
• Diagnosis confirmed by imaging:
  • Upper GI series
  • Hypotonic duodenography
  • Computed tomography

Management

• Primary goal is to correct the underlying cause, typically regain lost weight
• Acute treatment includes:
  • Adjusting body position to alleviate symptoms
  • Nasogastric decompression
  • Some patients may require a feeding tube distal to the obstruction or parenteral nutrition
• Surgery may be required, options include:
  • Strong's procedure: duodenum moved to the right of the SMA
  • Gastrojejunostomy
  • Duodenojejunostomy

Disposition

• Depending on the clinical presentation
• If complete obstruction, may require admission for decompression and nutrition