Superior Mesenteric Artery Syndrome - Diagnosis

Diagnosis

• Abdominal and pelvic computed tomography scan showing duodenal compression (black arrow) by the superior mesenteric artery (red arrow) and the abdominal aorta (blue arrow).

• Upper gastrointestinal series showing extreme duodenal dilation (white arrow) abruptly preceding constriction by the SMA.

• A diagram of a healthy mesenteric angle.

• A diagram of a compressed duodenum due to a reduced mesenteric angle.

Diagnosis is very difficult, and usually one of exclusion. SMA syndrome is thus considered only after patients have undergone an extensive evaluation of their gastrointestinal tract including upper endoscopy, colonoscopy, and evaluation for various malabsorptive, ulcerative and inflammatory instestinal conditions with a higher diagnostic frequency. Diagnosis may follow x-ray examination revealing duodenal dilation followed by abrupt constriction proximal to the overlying SMA, as well as a delay in transit of four to six hours through the gastroduodenal region. Standard diagnostic exams include abdominal and pelvic computed tomography (CT) scan with oral and IV contrast, upper gastrointestinal series (UGI), and, for equivocal cases, hypotonic duodenography. Once the diagnosis is made, vascular imaging studies such as ultrasound and contrast angiography may be used to indicate increased bloodflow velocity through the SMA, signifying risk of sudden, fatal circulatory collapse.

Despite multiple case reports, there has been controversy surrounding the diagnosis and even the existence of SMA syndrome since symptoms do not always correlate well with radiologic findings, and may not always improve following surgical correction. However, the reason for the persistance of gastrointestinal symptoms even after surgical correction has been recently traced to the remaining prominence of reversed peristalsis in contrast to direct peristalsis.

Since females between the ages of 10 and 30 are most frequently afflicted, it is not uncommon for physicians to initially and incorrectly assume that emaciation is a choice of the patient instead of a consequence of SMA syndrome in its chronic form. Patients in the earlier stages of chronic SMA syndrome often remain unaware that they are ill until substantial damage to their health is done, since they may attempt to adapt to the condition by gradually decreasing their food intake or naturally gravitating toward a lighter and more digestible diet. Eating disorder treatment protocols involving forced refeeding and behavioral therapy are noted to have poor outcomes with individuals suffering from SMA syndrome, contributing to the high mortality rate of the condition.