Superior Mesenteric Artery Syndrome

Clinical History

17 year old with ulcerative colitis, had undergone removal colon over course of 3 surgical procedures, the last being an ileostomy. A week later she developed intermittent colicky abdominal pain and vomiting. Discuss the differential diagnosis and the relevant investigations.

Imaging Findings

Patient diagnosed with Ulcerative Colitis and after failure of medical treatment had undergone a number of surgical procedures.These included a left hemicolectomy,a right colectomy with excision of the rectum with an ileoanal anastomosis and finally an ileostomy. A week after her ileostomy she developed intermittent colicky abdominal pain and vomiting. A subacute intestinal obstruction was suspected, and an abdominal X–ray was performed and found to be normal. An upper GI contrast then demonstrated hold up of contrast in the 3rd part of the duodenum (Fig 1a), which resolved upon placing the patient in the left-lateral position (Fig 1b).

Discussion

Superior mesenteric artery (SMA) syndrome, also known as Wilkie’s syndrome or Cast syndrome, is a rare clinical condition resulting from compression of the third or transverse parts of the duodenum by the SMA anteriorly and the aorta and vertebral column posteriorly. The result is an acute, intermittent or chronic form of duodenal obstruction. In 1861 Von Rokitansky first described the condition, and hypothesized that arteriomesenteric compression was the cause of duodenal obstruction. The incidence rate has been reported as 0.1%-0.3% with a slight female preponderance. The pathophysiology of the condition is believed to be due to a decreased angle between the aorta and SMA (normal angle range 38°-56°), and a narrowing of the arteriomesenteric angle (range 6°-16°). In both cases the third part of the duodenum becomes entrapped in its passage between the vessels. Another theory is that the retroperitoneal and mesenteric fat hold the SMA and root of the mesentery off the aorta and vertebral column, and any loss of these protective fat cushions predisposes to SMA syndrome. Predisposing factors include rapid weight loss, catabolic states (burns and cancer), head injuries, anorexia, bulimia, malabsorption, high fixation of the ligament of Trietz and a congenitally abnormal SMA-aortic angle. Spinal pathology and the application of body casts for correction of scoliosis are other causative factors (hence the term Cast syndrome). SMA syndrome has also been reported following ileal J-pouch anal anastomosis in the treatment of ulcerative colitis, and is thought to be due to traction on the mesentry. Presentation is usually with abdominal pain, bilious vomiting, postprandial nausea and weight loss. The symptoms may be relieved by lying in the left-lateral, knee-chest or prone position. The diagnosis is confirmed by an upper gastrointestinal contrast study, which demonstrates obstruction of the passage of contrast in the third part of the duodenum with a straight line cut-off and proximal dilatation. In the dilated portion reverse peristalsis may be seen. These features may disappear in the knee-chest (Hayes manoeuvre) or left-lateral position. Computed tomography is also useful in the diagnosis in demonstrating proximal duodenal distension, the amount of intra-abdominal and retroperitoneal fat and the SMA-aortic distance. The treatment of SMA syndrome is initially conservative. This includes lying in the left-lateral or knee-chest position after feeds, correction of electrolyte imbalance, passage of a nasogastric tube, and intravenous hyperalimentation. Surgical treatment is indicated when conservative measures fail. The procedure of choice is a duodeno-jejunostomy.

Differential Diagnosis List

Final Diagnosis

Superior mesenteric artery syndrome

URL:	https://www.eurorad.org/case/1173
DOI:	10.1594/EURORAD/CASE.1173
ISSN:	1563-4086