Chapter 406

Superior mesenteric artery syndrome (SMAS), also known as Wilkie syndrome, arteriomesenteric duodenal compression, chronic duodenal ileus, or cast syndrome, was first described by von Rokitansky in 1842, and is an unusual form of gastrointestinal obstruction resulting from compression of the duodenum between the abdominal aorta posteriorly and the superior mesenteric artery anteriorly (Fig. 406-1).1 In 1878, Willet documented the development of SMAS in association with orthopedic casting; however, it was not until 1927 that Wilkie formally characterized SMAS in a series of 75 patients.2,3 To date, the diagnosis, and to some extent the existence, of SMAS remains controversial as symptoms do not always correlate with radiologic findings and may not improve with surgical correction)

###### Figure 406-1.

Anterior-posterior and lateral illustration of the anatomic location of the stomach and duodenum in relation to the aorta and the superior mesenteric artery (SMA).

### Epidemiology

SMAS is a rare form of intestinal obstruction with a reported incidence ranging from 0.01% to 0.3%.4,5,6 SMAS is found more commonly in females than males and typically affects individuals of slender build after acute weight loss, such as from hyperthyroidism, anorexia nervosa, or even gastroenteritis. SMAS also affects individuals following orthopedic casting, especially following scoliosis surgery or following the application of a hip-spica cast.7 Acute or chronic neurologic injury is associated with superior mesenteric artery syndrome.8 Other associated disorders include fungal abscess, gastric bezoar, pregnancy, and aneurysms of the superior mesenteric artery.

### Pathophysiology

The superior mesenteric artery (SMA) usually arises from the anterior aspect of the aorta at the level of the first lumbar vertebral body and is surrounded by fat and lymphatic tissue. The artery then extends caudally at an acute angle into the mesentery. The duodenum passes between the aorta and the proximal SMA commonly at the level of the third lumbar vertebral body. The duodenum is suspended within the angle created by the aorta and SMA by the ligament of Treitz (Fig. 406-1). In the majority of the population, the angle between the superior mesenteric artery and the aorta is between 45 and 60 degrees. This angle is in part due to the presence of an anterior mesenteric fat pad, the size of which correlates with body mass index.9 In SMAS, the angle between the aorta and the SMA is reduced to as little as 6 degrees, allowing the SMA to compress the duodenum against the aorta, resulting in mechanical obstruction.

Although, to date, no genetic mutations have been associated with SMAS, Iwaoka documents the development of SMAS in identical twin males without any previous risk factors or surgeries.5 In addition, Ortiz reported a case of familial SMAS with 5 out of 8 family members developing SMAS, including a father and his ...

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