Clinical History
A 47-year-old male patient was admitted due to diffuse intermittent pain in the epigastrium and bilious vomiting during the past 2 weeks. The pain was associated with postprandial fullness. On physical examination the patient was emaciated, dehydrated, with diffuse abdominal pain. The patient was oligophrenic, with no other known clinical history.
Imaging Findings
Upper gastrointestinal barium study showed dilatation of the second part of duodenum with compression of the third part (Fig.1) Abdominal ultrasound revealed narrowing of the third duodenal segment between the aorta and superior mesenteric artery due to a reduced aorto-mesenteric space of 5mm (Fig.2).
Contrast enhanced CT was performed and confirmed the sonographic findings showing gastric and proximal duodenum distension caused by compression of the third portion of the duodenum due to marked narrowing of the aorto-mesenteric space (Fig.3). The aortomesenteric distance was reduced to 5mm (Fig.4) and the aorto-mesenteric angle, measured on reformatted sagittal CT images, was narrowed to 24º (Fig.5). There was no evidence of focal mass or bowel wall thickening of the stomach and duodenum.
Taking into account the clinical history and the imaging findings a diagnosis of superior mesenteric artery syndrome was made, which was confirmed at surgery. Duodenal mobilisation and duodenojejunostomy were performed to release the superior mesenteric artery compression.
Discussion
The Superior Mesenteric Artery Syndrome (SAMS), first described by Von Rokitansky in 1861 [1], is a very rare entity, with an incidence reported in the literature of approximately 0.2% [2]. It is characterised by severe compression of the third portion of the duodenum between the aorta and the SMA, leading to partial or complete duodenal obstruction.
Usually the third portion of the duodenum is surrounded by retroperitoneal fat and lymphatic tissue, which protect it from compression by the SMA. The SAMS can break out from any condition that involves a substantial loss of these tissues, thus conditioning a narrowing of the aorto-mesenteric angle with consequent compression of the third duodenal portion. Rapid and severe weight loss for any reason is the most common cause of SMAS, as in the presented case. Other possible risk factors that may precipitate the aortomesenteric angle reduction are prolonged immobilisation, exaggerated lumbar lordosis, external compression due to spinal body cast and also congenital anomalies such as a short or abnormally high insertion of the Treitz ligament [2].
Patients usually present with postprandial epigastric pain, nausea, early satiety and bilious vomiting.
The mortality rate is high, so early diagnosis is critical. However, its clinical diagnosis is difficult and requires confirmation by radiographic studies. Although upper gastrointestinal barium study had conventionally been used for the diagnosis of this syndrome, the radiological findings of this study are often nonspecific and multidetector-row CT has assumed an important role in its diagnosis [3].
Abdominal contrast-enhanced CT with 3D reformatting is a useful noninvasive diagnostic technique that provides good anatomical detail and allows an accurate measurement of the aorto-mesenteric angle and distance at the level of the third duodenal portion, which are the most important criteria for the diagnosis of SMAS. Normally, the aorto-mesenteric angle range from 38-56 ° and the normal aorto-mesenteric distance between 10 and 20 mm. SMAS usually develop when the aorto-mesenteric angle is less than 22° and the distance is less than 8 mm [4], as it was seen in our patient.
US can also demonstrate the short distance and the narrow angle between the aorta and SMA, as in our case. However US is more dependent on the patient’s body stature, the specifications of the US machine and the experience of the operator.
SMAS treatment consists of conservative measures such as prompt decompression of the stomach, fluid and electrolyte replacement therapy. Surgery, such as duodenojejunostomy, may be considered if conservative treatment fails [1].
Differential Diagnosis List
Superior mesenteric artery syndrome
Superior mesenteric artery syndrome
Idiopathic intestinal pseudo-obstruction
Connective tissue disorders
Final Diagnosis
Superior mesenteric artery syndrome
