Superior Mesenteric Artery Syndrome

Superior Mesenteric Artery (SMA) syndrome is a rare but serious condition characterized by compression of the third portion of the duodenum between the aorta and the superior mesenteric artery, resulting in partial or complete duodenal obstruction.

Key Points

• Prevalence: 0.013-0.3% of general population
• More common in females (F:M ratio 2:1)
• Peak age: adolescents and young adults
• Associated with rapid weight loss or conditions causing decreased retroperitoneal fat

Pathophysiology

• Normal aortomesenteric angle: 38-65 degrees
• Normal aortomesenteric distance: 10-28 mm
• In SMA syndrome:
• Angle reduced to 6-25 degrees
• Distance decreased to 2-8 mm

Risk Factors

• Severe weight loss
• Prolonged bed rest
• Spinal surgery or casting
• Eating disorders
• Malabsorption conditions
• Post-growth spurt adolescents
• Congenital anatomical abnormalities

Clinical Presentation

Common Symptoms

• Postprandial epigastric pain
• Early satiety
• Nausea and vomiting
• Weight loss
• Relief in prone or left lateral position
• Worsening in supine position

Physical Examination

• Abdominal tenderness
• Succussion splash
• Signs of malnutrition
• Decreased body mass index

Complications

• Electrolyte imbalances
• Dehydration
• Malnutrition
• Aspiration pneumonia
• Gastric perforation (rare)

Diagnostic Approach

Imaging Studies

• Upper GI series with contrast
• Dilated first and second portions of duodenum
• Abrupt cutoff in third portion
• "To-and-fro" peristalsis
• Delayed gastroduodenal emptying
• CT/MR angiography
• Measures aortomesenteric angle and distance
• Rules out other causes
• Gold standard for diagnosis
• Ultrasound
• Can measure aortomesenteric angle
• Less reliable than CT/MRI

Laboratory Studies

• Complete blood count
• Comprehensive metabolic panel
• Serum albumin
• Pre-albumin
• Electrolytes

Treatment Approaches

Conservative Management

• Initial approach for most patients
• Nutritional support
• Small, frequent meals
• Position change after meals
• High-calorie, high-protein diet
• Positional therapy
• Left lateral decubitus position
• Prone positioning
• Knee-chest position
• Nasogastric or nasojejunal feeding if needed
• Total parenteral nutrition in severe cases

Surgical Management

Indicated when conservative management fails after 4-6 weeks

• Strong's procedure
• Duodenojejunostomy
• Laparoscopic duodenojejunostomy
• Gastrojejunostomy

Monitoring and Follow-up

• Regular weight checks
• Nutritional status monitoring
• Growth velocity in children
• Quality of life assessment