What is the management of Superior Mesenteric Artery (SMA) syndrome?

Management of Superior Mesenteric Artery (SMA) Syndrome

The first-line treatment for SMA syndrome is conservative management with nutritional support, but surgical intervention with duodenojejunostomy is indicated when conservative measures fail or symptoms are severe.

Pathophysiology and Diagnosis

SMA syndrome occurs when the third portion of the duodenum is compressed between the abdominal aorta and the superior mesenteric artery, leading to partial or complete obstruction. This compression typically results from:

• Decreased aortomesenteric angle (normal >22°, in SMA syndrome ≤22°)
• Reduced aortomesenteric distance (normal >8mm, in SMA syndrome ≤8mm)
• Loss of retroperitoneal fat cushion

Diagnosis is established through:

• CT/MR angiography showing reduced aortomesenteric angle and distance
• Barium swallow demonstrating gastroduodenal dilation and delayed emptying
• Upper endoscopy to exclude other causes of obstruction

Management Algorithm

1. Conservative Management (First-Line)

• Nutritional Support:

  • Enteral feeding distal to the obstruction (nasojejunal tube)
  • Parenteral nutrition if enteral feeding is not tolerated
  • Small, frequent meals in left lateral or prone position
  • Hyperalimentation to restore retroperitoneal fat pad

• Supportive Care:

  • Nasogastric decompression for symptomatic relief
  • Fluid and electrolyte correction
  • Prokinetic agents to improve gastric emptying

Conservative management should be attempted for 4-6 weeks before considering surgical options 1, 2.

2. Endoscopic Intervention

• EUS-guided gastrojejunostomy may be considered in select patients, particularly those with comorbidities that increase surgical risk 3
• This approach allows for bypassing the obstruction while avoiding major surgery

3. Surgical Management

Surgical intervention is indicated when:

• Conservative management fails after 4-6 weeks
• Symptoms are severe or persistent
• Significant weight loss continues despite conservative measures
• Complications such as aspiration or severe malnutrition develop

Surgical options include:

1. Duodenojejunostomy (procedure of choice):

   • Open or laparoscopic approach
   • Creates a bypass between the second portion of the duodenum and proximal jejunum
   • Success rates of 80-90% for symptom improvement 4

2. Strong's procedure (duodenal mobilization with division of the ligament of Treitz)

3. Gastrojejunostomy (less preferred due to risk of continued duodenal distention)

A prospective study of 39 patients showed significant improvement in symptom scores and BMI following duodenojejunostomy, with benefits maintained at a median follow-up of 47 months 4.

Special Considerations

Monitoring Response to Treatment

• Regular assessment of nutritional status and weight gain
• Follow-up imaging (barium swallow) at 2 months post-intervention
• Symptom score evaluation

Pitfalls to Avoid

1. Delayed diagnosis: SMA syndrome is often a diagnosis of exclusion, leading to delayed treatment and worsening malnutrition

2. Inadequate nutritional support: Insufficient caloric intake perpetuates the cycle of weight loss and worsening compression

3. Premature surgical intervention: Surgery before adequate trial of conservative management may be unnecessary in some patients

4. Failure to address underlying conditions: Any predisposing conditions (rapid weight loss, eating disorders, spinal surgery) should be managed concurrently

Prognosis

With appropriate management, most patients with SMA syndrome experience significant symptom improvement. In the largest prospective study to date, surgical treatment resulted in:

• Significant reduction in overall symptom score (10 vs. 32, p<0.0001)
• Increased BMI (19.5 vs. 17.8 kg/m², p<0.0001)
• Improved gastroduodenal emptying in 38% of patients with preoperative pathological findings 4

However, surgery is not curative in all cases, and some patients may continue to experience symptoms despite intervention.