Epidemiology
Superior Mesenteric Artery (SMA) Syndrome is a rare condition resulting in vascular compression of the third portion of the duodenum by the SMA or its branches. The overall incidence is less then 0.5%, and it is more commonly seen in women, patients between the ages of 10 and 40, and patients who are either underweight or have had rapid weight loss (e.g. following a Roux-en-Y gastric bypass procedure) resulting in loss of the retroperitoneal fat pad.
Diagnosis
Symptoms generally consist of vague abdominal complaints such as epigastric pain, early satiety, post-prandial fullness, and relief of pain with a prone or knee-to-chest position.
Imaging studies may include SMA angiography, CT scan with 3D reconstructions, upper GI series, or fluoroscopy in the prone or knee-to-chest-position, and may demonstrate dilation of the stomach and first and second portions of the duodenum, decompression of the third portion of the duodenum, an aortomesenteric angle ranging from 1 to 40 degrees (normal 18 to 70), or an aortomesenteric distance ranging from 2 to 8 mm (normal 10 to 28 mm).
Treatment
The initial treatment is non-operative and focuses on correction of malnutrition and repletion of the retroperitoneal fat pad. Measures include frequent, high-calorie, pureed meals; supplementation via a nasojejunal feeding tube; or, rarely, parenteral nutrition.
If symptoms fail to improve with nutritional support, operative intervention may be required. The most commonly accepted procedures are:
1) Division of the ligament of Treitz +/- mobilization of the duodenum
2) Anterior transposition of the duodenum
3) Duodenojejunostomy +/- division of the ligament of Treitz
Less frequently, Roux-en-Y duodenojejunostomy, Omega-loop gastrojejunostomy, circular drainage of the duodenum, or Roux-en-Y gastrojejunostomy have been reported.
Division of the ligament of Treitz
Incision of the peritoneum along the left side of the duodenojejunal junction to expose and subsequently divide the ligament of Treitz allows the duodenum to fall several centimeters inferiorly and is associated with a cure rate in excess of 75%.
Anterior transposition of the duodenum
The duodenum is fully mobilized, including division of the ligament of Treitz, after which the third portion of the duodenum is transected to the left of the SMA and reanastomosed anterior to the vessels. In one small case series, cure rate was 100%.
Duodenojejunostomy
The procedure of choice is duodenojejunostomy with division of the ligament of Treitz. The duodenum is fully mobilized and a side-to-side duodenojejunostomy is created proximal to the obstruction. With duodenojejunostomy alone, cure rate is in excess of 80%, and when combined with division of the ligament of Treitz, this increases to approximately 98%.
Laparoscopic Approach
Any of the above procedures may be performed laparoscopically using four to five ports placed through the umbilicus and along the right and left costal margins. Small series have reported success rates of 75-100% with laparoscopic division of the ligament of Treitz or laparoscopic duodenojejunostomy using a retrocolic stapled anastomosis.