Superior mesenteric artery (SMA) syndrome results from vascular compression of the third portion of the duodenum between the SMA anteriorly and the abdominal aorta posteriorly (Fig. 401-1). This syndrome has also been termed Wilkie syndrome, arteriomesenteric duodenal compression, chronic duodenal ileus, or cast syndrome. This syndrome is relatively rare, especially in the pediatric population, and can be difficult to diagnose. It is confused commonly with other anatomic or motility-related causes of duodenal obstruction.
This figure depicts the normal anatomic relation between the duodenum, superior mesenteric artery (SMA), and aorta. The SMA passes over the duodenum, positioning the duodenum between itself and the aorta. In addition, the third portion of the duodenum is fixed at the level of the third lumbar vertebral body where it is suspended by the ligament of Treitz.
PATHOGENESIS AND EPIDEMIOLOGY
The duodenum passes between the SMA and the aorta. In addition, the third portion of the duodenum is fixed at the level of the third lumbar vertebral body where it is suspended by the ligament of Treitz (Fig. 401-1). The angle between the SMA and the aorta, the aortomesenteric angle, is usually 38° to 65°. This angle is maintained by the mesenteric fat pad, which correlates highly with body mass index (BMI). The distance between the SMA and the aorta is usually 1 to 2 cm. In SMA syndrome, the angle may be narrowed to as low as 6° and the aortomesenteric distance shortened to as low as 2 mm.
Carl von Rokitansky was the first to observe SMA syndrome in 1861 and David Wilkie published the first comprehensive data set on 75 patients in 1927. The reported incidence of SMA syndrome is only between 0.01% and 0.3%. It is seen more commonly in females than in males and in older children and adolescents. SMA syndrome is often associated with rapid weight loss prior to the onset of symptoms.
CLINICAL FEATURES AND DIFFERENTIAL DIAGNOSIS
SMA syndrome is frequently associated with preceding weight loss, rapid linear growth, paraplegia, and an abnormally high position of the ligament of Treitz. It is also seen in debilitating illnesses such as malignancy, malabsorption syndromes, trauma, and burns. Corrective surgery for scoliosis is a risk factor for SMA syndrome in younger patients. The lateral mobility of the SMA is decreased and the acuteness of the aortomesenteric angle is reduced, leading to symptoms.
Patients typically present with vague symptoms, including abdominal pain, nausea, vomiting, anorexia, weight loss, and early satiety. Symptoms may appear acutely or be chronic in nature. Patients may be seen lying in the left lateral decubitus, in a knee-chest position, or prone to relieve their symptoms. Complications from delayed diagnosis include an obstructing duodenal bezoar, gastric pneumatosis, and portal venous gas, ...