Teaching Case

A 34-year-old man was diagnosed with type 1 diabetes a year ago and incompliant regarding his treatment. Due to weight loss of 10kg, reduced appetite, diarrhoea and an epigastric mass, he was referred to the hospital with the tentative diagnosis of pancreatic cancer. At admission, BMI was 15.8.

A contrast-enhanced CT scan showed a full and distended stomach. Findings were normal regarding the solid organs and no tumour was diagnosed. A fluoroscopy of the stomach with oral contrast was done, due to the distended stomach. After 90 minutes the majority of contrast remained in the fundus of the stomach.  A tiny amount of contrast had passed into the small intestine. The conclusion was reduced motility and reduced passing of oral contrast through the stomach. The CT images were revisited and revealed findings of a narrow-angle of 22⁰  between the aorta and the superior mesenteric artery (SMA), and only 6mm distance between the two at the level of the third part of duodenum. These findings suggested superior mesenteric artery syndrome (SMA syndrome).

SMA syndrome is a rare disease characterized by partial or full compression of the third part of the duodenum by the SMA and the aorta. The compression occurs as a result of loss of retroperitoneal fat in relation to the SMA. The end result is a narrowing of the angle and distance between aorta and SMA. Compression of the duodenum is often seen when the angle decreases to 22⁰ or less and the distance decreases to 8mm or less [1]. Both the distance and the angle between the aorta and SMA is correlated with BMI [2]. Most cases of SMA syndrome involve severe weight loss due to other factors such as anorexia nervosa, malignancies, large burns etc.; weight loss subsequently further exaggerated by the partial or full duodenal obstruction [1]. The Incidence of SMA syndrome is largely unknown but is estimated to be 0.013%-0.3% with a 3:2 female to male ratio and often patients are aged 10-39 [3].

   Here we present a case where incompliance related to diabetes treatment was the probable cause of the initial weight loss, which was most likely exacerbated by loss of retroperitoneal fat leading to SMA syndrome. Similar cases have been reported [4]. Reaching the diagnosis was difficult as SMA syndrome is rare and the patient did not have full obstruction of the duodenum, and no complaints of bilious emesis or other symptoms that would suggest high obstruction. The patient was treated with endoscopic placement of a 3-lumen tube, with one lumen placed after the duodenojejunal flexure. The goal was for the patient to gain 10kg. At the time of writing the patient has gained 2kg and reports fewer problems with nausea and slightly better appetite. In many cases, SMA syndrome can be treated conservatively by regaining weight, either with or without an endoscopic tube. When conservative treatment fails duodenojejunostomy is often the preferred surgical intervention [5].

   Presented with a patient with severe weight loss and low BMI, the radiologist should consider SMA syndrome. Cross-sectional imaging with MPR by CT- or MR-angiography allows for the measurement of the angle between SMA and aorta (sagittal plane) as well as the distance between the two at the level of the third part of the duodenum (axial plane); thereby, the radiologist can determine if the patient might suffer from SMA syndrome. Severity of duodenal obstruction can be evaluated by dynamic fluoroscopy using oral contrast. 

Written informed patient consent for publication has been obtained.