**2. Anatomy and pathology**

The superior mesenteric artery (SMA) originates behind the neck of the pancreas at the level of the first lumbar vertebra and leaves the aorta at an acute angle. It forms an angle of approximately 45° with the abdominal aorta. The third part duodenum crosses caudal to the origin of superior mesenteric artery (SMA), coursing between SMA and aorta just inferior to the left renal vein from right to left (Fig 1). Any factor that sharply narrows the aortomesenteric angle from approximately 45º (range between 38-56°) to 6-25° will thus reduce the aortomesenteric distance to about 2-8mm (Hines et al 1984, Neri et al 2005). The mean radiographic aortomesenteric distance is 10–28 mm (Neri et al 2005).This can cause entrapment and compression of the third part of duodenum. Thus conditions such as loss of mesenteric and retroperitoneal fat and subsequent decrease of the aortomesenteric distance can cause SMAS.

#### **3. Causes**


Superior Mesenteric Artery Syndrome 417

Lee, Mangla 1978). CT or CT angiogram is also superior to ultrasound because it can measure the reduced aortomesenteric angle and show the gastric and duodenal dilatation at the same time. CT scan will also be helpful in finding the cause of SMAS e.g high insertion of ligament of Trietz or a neoplasia in that region. Upper gastrointestinal endoscopy is essential to rule out mechanical outlet obstruction of stomach or an ulcer (Ylinen et al 1989,

If there is a neoplasm causing SMAS, anatomic or congenital abnormality then the treatment is surgical, otherwise this condition is treated conservatively. Patients are fed frequent small meals orally or if it is not possible then through enteral jejunal tube. After feeding the patient, he/she should be placed in either prone or lateral decubitus position. If patient cannot tolerate tube feeding because of excessive vomiting then he/she needs to be fed parentally. Both ways of feeding have shown to be effective (Barnes, Lee 1996).This conservative treatment should aim to correct the fluid and electrolyte balance and increase the body weight in an attempt to

Surgical treatment is indicated if conservative treatment fails or if there is severe progressive weight loss, pronounced duodenal dilatation with stasis and complicating peptic ulcer disease. Several surgical procedures have been tried and tested in the management of SMAS. Gastrojejunostomy, dudenojejunostomy, Strong's operation (duodenal mobilisation for lowering the duodenojejunal flexure) have been performed to treat this condition. Gastrojejunostomy and lysis of the ligament of Treitz provided adequate decompression of the stomach but was not helpful in overcoming the duodenal obstruction and at times leading to blind loop syndrome with reflux of bile necessitating duodenojejunostomy (Lee, Mangla 1978). A review of 146 cases showed that duodenojejunostomy was the treatment of the choice (Lee, Mangla 1978) and success rate was 90 %(Raissi et al 1996). Recently laparoscopic dudenojejunostomy has become treatment of choice. Massoud (1995) reported his experience of laparoscopic division of the ligament of Treitz in 4 cases. It was successful in 3 cases. Gerson and Heniford (1998) reported first laparoscopic duodenojejunostomy and then further cases were reported in the literature (Richardson, Surowiec 2001). Minimally invasive surgery with less operative time, quick post operative recovery and relief of the

SMAS is a rare disorder and is under-diagnosed in our practice of medicine. It should be ruled out in the patients with postprandial abdominal pain, vomiting and weight loss. It is caused by compression of the third part of duodenum by the narrowed aortomesenteric angle. There are different predisposing factors but severe weight loss and cachexia, spinal deformities and congenital anomalies are some of them. SMAS is treated initially

Barnes JB, Lee M (1996) Superior mesenteric artery syndrome in an intravenous drug abuser

conservatively but laparoscopic duodenojejunostomy has high success rate as well.

increase the retroperitoneal fat so that the aortomesenteric angle is corrected.

symptoms were the advantages over traditional duodenojejunostomy.

after rapid weight loss. *South Med J.* 89: 331–334.

Raissi et al 1996).

**6. Treatment** 

**7. Conclusion** 

**8. References** 

Fig. 1. Left, the normal angle between the superior mesenteric artery (SMA) and the aorta is 25 to 60 degrees. Right, in SMA syndrome, the SMA-aortic angle is more acute, and the duodenum is compressed between the aorta and the SMA (Reproduced with permission from Pasumarthy et al (2010) Cleveland Clinic Journal of Medicine. 77:45-50)

