Unusual presentation of superior mesenteric artery syndrome in a child

Abstract

Superior mesenteric artery syndrome (SMAS), also known as Wilkie’s syndrome, is a rare cause of upper gastrointestinal tract obstruction. We report a case of a 10-year-old girl with persistent abdominal pain for over 3 months, who on extensive investigations was diagnosed with SMAS. She underwent a surgical procedure to bypass the obstructed portion of the intestine for relief of her symptoms.

Background

Superior mesenteric artery syndrome (SMAS) is defined as an intestinal obstruction caused by extrinsic compression of the third part of the duodenum between the abdominal aorta and the origin of superior mesenteric artery (SMA). In 1861, Austrian professor Carl Freiherr von Rokitan-sky reported SMAS as an autopsy finding.¹ In 1927, Wilkie formally characterised its pathophysiology and diagnostic findings.² It has an estimated incidence of 0.01%–0.3% in the paediatric population. It is commonly reported between 10 and 39 years of age, with a female to male ratio of 3:2.³

Case presentation

A 10-year-old girl presented with a complaint of dull continuous upper abdominal pain, localised in the epigastric region since 3 months. There was postprandial aggravation of pain, which was not relieved by medication. She also had a history of multiple episodes of vomiting which were non-bilious in nature. Her oral intake had reduced in the few weeks prior to presentation. She was being managed conservatively by local physicians, with oral analgesic and anti-emetics coupled with nutritional supplements and high-protein diet. She was provided with a diet chart to take frequent small high-calorie meals during the day. However, the patient was not consistently compliant with the conservative management and had recurrent symptoms. On investigation, a barium follow through visualised smooth passage of contrast throughout the gastrointestinal (GI) tract while the ultrasound scan of abdomen reported a segmental circumferential thickening of the sigmoid colon. This was followed up with contrast-enhanced CT scan which reported an acute angulation of the SMA resulting in the obstruction of the third part of the duodenum, with dilatation of the proximal duodenum and stomach (figure 1). An upper gastrointestinal (UGI) endoscopy revealed no intrinsic obstruction. Based on the reports, conservative management was continued with dietary modifications for about 4 months. However, there was no record of any significant weight loss or gain from the beginning of her symptoms as well as throughout the conservative management trial.

Figure 1.

Axial and sagittal sections of the CT scan showing duodenal obstruction between aorta and superior mesenteric artery (SMA).

At presentation to our institute, the patients’ vital signs were normal but she looked anxious. She weighed 22.6 kg, between 3rd and 10th centile, and had a height of 129 cm, between 10th and 25th centile, as per WHO growth chart for her age. She had a diffusely tender upper abdomen. The clinical symptoms were suggestive of a proximal duodenal obstruction but the radiological findings were consistent with the diagnosis of SMAS. Thus, we repeated an ultrasound of the abdomen. It reported an aortomesenteric angle of <21° with aortomesenteric distance of <3 mm, consistent with diagnosis of SMAS. Medical causes like tuberculosis, hyperthyroidism and coeliac disease were ruled out with blood investigations. Since there was no history of any recent significant weight loss or medical conditions resulting in these symptoms, our patient likely had a congenital cause for SMAS.

Differential diagnosis

This includes conditions like peptic ulcers, pancreatitis or eating disorders.

Treatment

A repeat UGI endoscopy demonstrated mucosal hypertrophy in the first and second part of the duodenum with inability to negotiate the scope beyond the second part of the duodenum. Biopsy samples were taken from the duodenum, which were later reported to be consistent with chronic duodenitis and Brunner gland hyperplasia. Then we proceeded for laparoscopy which showed a dilated second part of the duodenum without involvement of any other segment of bowel. The procedure was converted to a laparotomy. The entire bowel was reinspected from ileo-colic to duodeno-jejunal junction. The first and second part of the duodenum were dilated. A large bore nasogastric tube was manipulated until the jejunum to rule out luminal obstruction. Kocherisation of the duodenum was done followed by widening and release of the prominent ligament of Treitz. A jejunal loop was transected and an infra-colic side to side anastomosis of distal jejunal transected loop was done to the second part of the duodenum (figure 2). A 30 cm Roux loop was measured and proximal end of the transected jejunum was anastomosed in an end-to-side manner.

Figure 2.

Infra-colic anastomosis of the second part of the duodenum and jejunum.

Outcome and follow-up

The patient had an uneventful postoperative recovery. Oral liquids were started by post-operative day -4 and escalated gradually to solids by POD-9. She has been on regular follow-up for the past 7 months with no recurrence of symptoms. She currently weighs 26 kg (weight gain of 4 kg).

Discussion

SMAS or Wilkie’s syndrome is a rare cause of duodenal obstruction by an overlying SMA.⁴ The SMA originates at the first lumbar vertebral level from abdominal aorta and forms an acute downward angle from its anterior aspect. This angle normally ranges from 25° to 60° and the distance is about 10–20 mm. It is maintained by the mesenteric pad of fat, retroperitoneal lymphatics, uncinate process of the pancreas and left renal vein.⁵ Within this angle, the distal duodenum is suspended by the ligament of Treitz.

With a reduction in the aortomesenteric angle ranging between 6° and 15° and the aortomesenteric distance of 2–8 mm, compression of the duodenum can occur between SMA and aorta (figure 3). This extra-luminal entrapment of the third part of the duodenum may result in complete or partial duodenal obstruction.⁶ Occasionally, duodenum is elevated to more cranial position within the aortomesenteric angle due to a short mesenteric root⁷ or low origin of SMA,⁸ or high insertion of ligament of Treitz at the duodeno-jejunal flexure.⁹ Acquired causes involve drastic weight loss or dietary disorders like malabsorption syndrome and anorexia nervosa.¹⁰

Figure 3.

Diagrammatic representation of duodenal compression between the aorta and origin of the superior mesenteric artery (illustrated by Dr Shruti Tewari).

In most cases, significant weight loss appears to be the underlying cause. However, there was no such history in our case and surgical exploration was suggestive of a congenital short ligament of Treitz. The duodenum was abnormally raised in a cephalic position, causing it to get obstructed at the angle between aorta and the origin of SMA.

Presentation can be acute or chronic with symptoms like nausea, vomiting, anorexia and abdominal pain, mostly localised in the epigastric region. Early satiety and sensation of fullness due to increased gastroduodenal transit time may lead to weight loss and reduced oral intake.¹¹

An insidious presentation makes the diagnosis challenging, thus radiographic studies are necessary. Plain abdominal film may be non-specific, revealing proximal dilated duodenal loop and absence of distal bowel gas. Contrast study demonstrates dilated proximal duodenum with cut-off or delayed contrast passage beyond the third part of the duodenum. Ultrasound can visualise the dilated loops and measure the aortomesenteric angle. Contrast-enhanced CT is the gold standard investigation, providing detailed local anatomy and accurately measuring the aortomesenteric angle and distance.¹² Upper GI endoscopy may rule out possible intraluminal obstruction or presence of an ulcer mimicking symptoms of SMAS.

The initial management is conservative. Small frequent high caloric oral feeds help to improve weight and regain the lost mesenteric fat pad to relieve duodenal compression. Nutrition can also be improved by nasogastric tube placement for continuous enteral feeds or introduction of partial/total parenteral nutrition. Prokinetic drugs can be added to improve motility and enhance stomach emptying. Despite all measures, greater than 75% of patients eventually require surgical intervention.¹³

Surgical management entails mobilising the duodenum or bypassing its obstructed portion.¹⁴ A Roux-en-Y duodeno-jejunostomy is highly preferred in paediatric age group. It has a high success rate (~90%) as it is a physiological bypass. Laparoscopic duodeno-jejunostomy or severing of the ligament of Treitz is also done.¹⁵

A lack of guidelines remains a roadblock for the timely diagnosis and prompt treatment of Wilkie’s syndrome. Bypassing the obstructed duodenal segment by duodeno-jejunostomy may cause gastroparesis, due to gastric and duodenal flaccidity.¹⁶ Other reported complications related to SMAS include dehydration, metabolic imbalance and, rarely, death.

Patient’s perspective.

I was very worried as my child had been suffering for months despite being on medications and undergoing multiple investigations. We were apprehensive about getting surgery for her but it has been a real boon as she is finally pain free. In the past few months, she has been getting back to her normal self.

Learning points.

• Superior mesenteric artery syndrome (SMAS) should be considered as a differential diagnosis in a young patient presenting with persistent vomiting, even in the absence of a significant weight loss history.

• A contrast-enhanced CT scan is the most useful investigation in the definitive diagnosis of SMAS.

• Early surgical intervention should be considered, especially in the case of children, as they may be non-compliant with prolonged conservative management.

Ethics statements

Patient consent for publication

Consent obtained from parent(s)/guardian(s)