Teaching Case

A 55-year-old female patient presented to the radiology department with longstanding post-prandial epigastric pain and bloating. She had also lost 3 kilograms of weight recently. The epigastric pain aggravated and occurred even after very small meals. Oesophagogastroduodenoscopy revealed no abnormalities.

Ultrasound of the abdomen showed multiple tortuous parauterine vessels at the left hemipelvis (Fig. 1). The other organs of the abdomen were unremarkable.

CT showed compression of the third part of the duodenum with a small angle between the superior mesenteric artery (SMA) and the aorta. The distance between the aorta and SMA was narrowed. The duodenum proximal to the crossing of the SMA was slightly dilated. (Fig. 2a-c)

In addition to duodenal compression, the left renal vein was compressed by the SMA, causing secondary dilatation of the left renal vein, left ovarian vein and varices of the left parauterine venous plexus. (Fig. 2d-f)

Superior mesenteric artery (SMA) syndrome, also called Wilkie's syndrome, is a condition caused by compression of the third part of the duodenum between the SMA and the aorta. It was first described by Rokitansky in 1861 and later by Wilkie. The syndrome may rarely cause duodenal obstruction. [1-4]

The third part of the duodenum crosses the SMA and aorta. Loss of mesenteric and retroperitoneal fat in this region (e.g. due to anorexia nervosa, burns, malignancies), a short ligament of Treitz and an unusual low origin of the SMA can cause narrowing of the space for the duodenum. The mean aortomesenteric distance is 10mm-28mm. [2-4] Some authors recommend measurement of the aortomesenteric angle as a diagnostic parameter [4], although the large variability (25°-60°) may reduce the value of this measurement.

The SMA syndrome affects women more frequently. It is also more common in tall and slender people. [1, 3] Symptoms of SMA syndrome are nonspecific and include nausea, vomiting, post-prandial epigastric pain, bloating and weight loss. [1-3] Symptoms start or aggravate after eating and can be relieved by postural changes such as turning to the left side, in prone or knee-chest position. [1, 2]

Previously, angiography has been suggested as the "gold standard" for diagnosis. Nowadays, computed tomography (CT) is considered the most valuable technique. It can both be used to show dilatation of the proximal duodenum and to measure the aortomesenteric angle and distance. CT is also very helpful to rule out other causes of congenital or acquired duodenal obstruction (see differential diagnosis list). Plain films and barium studies are less sensitive and specific than CT. Oesophagogastroduodenoscopy is only useful to see extrinsic compression of the duodenum. [2-4]

Conservative treatment consisting of restoration of the mesenteric and retroperitoneal fat by a high caloric diet is recommended. This is more successful in patients with a short history of symptoms. Surgical therapy is recommended if conservative therapy fails. [1, 2]

The nutcracker phenomenon is another form of compression by the SMA. The left renal vein can become entrapped similarly as the duodenum causing dilatation of the left renal vein, left gonadal vein and the uterine respectively pampiniform venous plexus in female respectively male patients. It can co-occur with the SMA syndrome. If the dilatation becomes symptomatic, the term nutcracker syndrome is used. The most frequent symptoms are haematuria, flank pain, pelvic varicosities in women and varicocele in men. Asymptomatic patients do not require treatment. [1, 5]