Superior mesenteric artery syndrome is an unusual cause of proximal intestinal obstruction. It has been referred to by a variety of other names including Cast syndrome, Wilkie syndrome, arteriomesenteric duodenal obstruction, and chronic duodenal ileus [1,2]. The syndrome is characterized by compression of the third portion of the duodenum due to narrowing of the space between the superior mesenteric artery and aorta and is primarily attributed to loss of the intervening mesenteric fat pad.
There remains some controversy surrounding a diagnosis of superior mesenteric artery syndrome since symptoms do not always correlate well with abnormal anatomic findings on radiologic studies, and symptoms may not resolve completely following treatment [3,4]. Furthermore, the diagnosis may be confused with other anatomic or motility-related causes of duodenal obstruction .
The diagnosis and treatment of superior mesenteric artery syndrome will be reviewed here. The management of bowel obstruction is discussed elsewhere. (See "Epidemiology, clinical features, and diagnosis of mechanical small bowel obstruction in adults" and "Overview of management of mechanical small bowel obstruction in adults".)
The third portion of the duodenum passes between the aorta and the superior mesenteric artery (figure 1 and image 1). The duodenum typically crosses anterior to the aorta at the level of the third lumbar vertebral body suspended by its attachment to the ligament of Treitz.
The superior mesenteric artery arises from the anterior aspect of the aorta at the level of the L1 vertebral body. It is enveloped in fatty and lymphatic tissue and extends in a caudal direction at an acute angle into the mesentery. In the majority of patients, the normal angle between the superior mesenteric artery and the aorta is between 38 and 65º due, in part, to the mesenteric fat pad . This angle correlates with body mass index . The aorto-mesenteric distance is normally 10 to 28 mm .