Superior mesenteric artery (SMA) syndrome is an uncommon cause of intestinal obstruction due to vascular compression of the third portion of the duodenum (D3) between the aorta and the SMA. It was first described in an anatomy text by Austrian professor Carl von Rokitansky in 1861. Wilkie subsequently published the first comprehensive series of 75 patients in 1927, and his name became an eponym for the syndrome.
The SMA originates from the anterior surface of the abdominal aorta just inferior to the origin of the celiac trunk at the level of the first lumbar vertebra. It then courses anteroinferiorly behind the neck of the pancreas to create the aortomesenteric angle, embedded with retroperitoneal fat tissue and lymphatics. The third portion of duodenum is suspended within this angle by the suspensory ligament of Treitz and crosses the vertebral column at the level of the third lumbar vertebrae.
Under normal conditions, the mass of fat and lymphatic tissue surrounding the SMA origin forms a physiologic "fat pad" that surrounds and protects the duodenum against vascular compression. Loss of this buffer results in narrowing of the vascular angle and the development of SMA syndrome (SMAS). The normal angle between the aorta and the SMA ranges from 38°-65°, and the normal aortomesenteric distance ranges from 10-28 mm. In SMAS, the angle is decreased to 6°-25°, and the aortomesenteric distance is decreased to 2-8 mm.
SMAS has an estimated prevalence of 0.013%-0.3% in the general population.[5,6] Females are more commonly affected than males, and most cases are diagnosed between age 10 and 39 years, with a median age of 28 years.[4,7] Individuals with conditions causing catabolic states or severe weight loss are at particular risk. owing to depletion of the mesenteric and retroperitoneal fat surrounding the SMA. This leads to reduction of the aortomesenteric angle and subsequent duodenal obstruction.[5,7]
Both acute and chronic forms of SMAS have been described. The most common comorbidities are mental and behavioral disorders (eg, anorexia nervosa, drug abuse), infectious diseases, and diseases of the nervous system (eg, cerebral palsy, paraplegia, juvenile rheumatoid arthritis, brain injury). Numerous predisposing conditions have been identified, including chronic wasting diseases (eg, cancer, cardiac cachexia, malabsorption, hyperthyroidism), trauma (eg, severe burn injury, polytrauma), postoperative states (eg, bariatric surgery, Nissen fundoplication, posterior spinal fusion or scoliosis surgery, body cast, proctocolectomy, ileoanal pouch anastomosis), anatomical and congenital anomalies (eg, intestinal malrotation, high insertion of the ligament of Treitz, low origin of the SMA, increased lumbar lordosis), and local pathology (eg, neoplastic growth in the mesenteric root, dissecting aortic aneurysm).[3,7,8]
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