Superior mesenteric artery syndrome

Clinical History

The patient underwent computed tomographic examination to investigate vomiting, abdominal swelling, weight loss of 10kg and loss of appetite. Previous history of ovarian and peritoneal cancer with chemotherapy were completed 3 months before.

Imaging Findings

Computed tomography shows gastric distension, significant reduction in intraabdominal fat and reduced angle between superior mesenteric artery and aorta (11 degrees).

Discussion

Superior mesenteric artery (SMA) syndrome is a rare entity characterized by extrinsic compression of the third part of the duodenum by the superior mesenteric artery anteriorly, and aorta and vertebral column posteriorly [1]. Women are more commonly affected by SMA syndrome, with two-thirds of patients being between 10 and 39 years of age [1].
Normally, the third part of the duodenum is surrounded by retroperitoneal fat, which provides a “cushion” for duodenum between anterior SMA and posterior aorta and helps maintain a wide aortomesenteric angle (AMA) and aortomesenteric distance (AMD) [7].The AMA and AMD in patients with SMA syndrome have been reported to be 6°–22° and 2–8 mm, respectively [4, 5, 6, ]. In a recent multidetector CT study of four cases of SMA syndrome, the mean AMA and AMD were 13.5° and 4.4 mm, respectively [7].
Causes of reduction of AMD and AMA occur in conditions associated with rapid and severe weight loss, resulting in a loss of retroperitoneal fat, such as acquired immunodeficiency syndrome, malabsorption and others; catabolic conditions such as burns and major surgery; eating disorders (e.g., anorexia nervosa); drug abuse [1, 6]; In patients who have undergone corrective surgery for scoliosis, in whom lengthening of spine is postulated to increase tension on mesentery and thus decrease AMA and AMD [8, 9]; Conditions involving applied external abdominal pressure such as from a body or hip spica cast [10]; and anatomic variants such as an insertional variation of Treitz ligament or low origin of SMA, which may result in a more cranial disposition of duodenum into acute vascular angle between aorta and proximal SMA [1, 11].
Traditional imaging methods for diagnosis include an upper gastrointestinal barium study and conventional mesenteric angiography [2, 3], which only allow evaluation of the gastrointestinal tract and vascular anatomy, respectively [3, 4]. CT performed after the injection of iodinated contrast material allows simultaneous evaluation of the mesoaortic vascular anatomy, transverse duodenal compression, and proximal dilatation, and is thus the diagnostic test of choice for SMA syndrome [2, 5]. It is best performed in late angiographic phase to allow simultaneous optimal depiction of vascular anatomy and bowel wall. Positive oral contrast agent use may be avoided in patients with severe obstruction. Sagittal MPR images are needed to evaluate the AMA. CT has the added advantage of showing exact anatomic position of duodenum in vascular angle and excluding other causes of obstruction. However, SMA syndrome should not be diagnosed solely on the basis of CT findings of a reduced AMA and AMD in absence of any signs or symptoms of duodenal obstruction [7].

Differential Diagnosis List

Final Diagnosis

Superior mesenteric artery syndrome

URL:	https://www.eurorad.org/case/11798
DOI:	10.1594/EURORAD/CASE.11798
ISSN:	1563-4086