Teaching Case

An 18-year-old poorly built ( BMI = 17 kg / sq m ) female patient with complaints of chronic intermittent postprandial epigastric pain and occasional episodes of vomiting with normal routine lab investigations and no previous comorbidities.

Contrast CT abdomen showed a characteristic hooked appearance with focal narrowing of the proximal celiac axis and post stenotic dilatation in sagittal plane ( fig 1 ) suggestive of median arcuate ligament syndrome (MALS)
Aorto-mesenteric angle (AMA) measured 19.5° (Fig. 2)and aortomesenteric distance ( AMD ) was 7.35 mm (Fig. 3 ). Dilatation of the proximal portion of 3rd part of duodenum with reduced AMA and AMD was suggestive of Wilkie’s syndrome.
Characteristic beak sign with abrupt narrowing of the left renal vein (LRV) between the aorta and superior mesenteric artery (SMA), with proximal dilatation of the LRV, was seen (Fig. 4). Reduced AMA measuring 19.5 °, LRV diameter ratio of 5.6 (ratio of diameter of LRV at hilum to the diameter at aortomesenteric region) (Fig. 5) and increased beak angle measuring 40.6° (Fig. 6) was obtained suggestive of nutcracker phenomenon.  

Abdominal vascular compression syndromes can either be compression of vascular structures or compression of abdominal viscera by vascular structures. Median arcuate ligament syndrome (MALS), Wilkie’s syndrome and nutcracker phenomenon occurring concurrently in the same patient is extremely rare [1] Marked weight loss, low body mass index (BMI ), post hip/body spica cast and post scoliosis surgical status are known risk factors [2], [3], [4] 

MALS is a rare abdominal vascular compression syndrome in which there is an indentation on the celiac axis by a low lying fibrous arch called median arcuate ligament which unites the diaphragmatic crura on either side of the aortic hiatus. In the sagittal plane, a characteristic hooked appearance with focal narrowing of the proximal celiac axis visible on inspiratory CT angiogram is the diagnostic finding. It is associated with post stenotic dilatation or collateral vessel formation from the branches of SMA. [5]

Wilkie's syndrome (also known as SMA syndrome/aortomesenteric duodenal compression syndrome) is caused by compression of the third part of the duodenum between the SMA and aorta as a result of loss of adipose tissue between them. The diagnostic findings include

• an AMA of less than 22° 
• AMD of less than 8 mm [6]. 

 The normal AMD is typically between 10 and 34 mm and is measured at the level of the duodenum as it travels between the aorta and SMA, and the normal AMA is between 28-65 ° [7]

Nutcracker phenomenon refers to compression of left renal vein (LRV) between SMA and aorta (anterior nutcracker) or between aorta and vertebral body (posterior nutcracker ) with no clinical symptoms. Symptoms like haematuria, flank pain, varicocele, orthostatic proteinuria and orthostatic intolerance with relevant radiological findings are called nutcracker syndrome.[8] This condition can lead to renal venous hypertension with left renal vein thrombosis and eventual formation of pelvic varices. [9] CT findings include 

• The beak sign (abrupt narrowing of the LRV between the aorta and SMA, with proximal dilatation of the LRV) 
• Narrow AMA < 41°
• LRV diameter ratio > 4.9 ( ratio of diameter of LRV at hilum to the diameter at aortomesenteric region )
• Beak angle >32 ° (angle between a line drawn from anterior wall of LRV where it passes deep to SMA to point of LRV narrowing, and another line drawn from posterior wall of LRV to point of narrowing). [10], [11] 

The initial management for all 3 conditions mentioned above is conservative by insertion of a nasogastric tube, and by enteral feeding for restoration of the aortomesenteric fatty tissue. [12]. For the treatment of Wilkie’s syndrome, lying in right decubitus position and postural corrections like Hayes manoeuvre in which pressure is applied below the umbilicus in a cephalic and dorsal direction and thereby relaxing the small bowel mesentery can be used to relieve duodenal compression. [13]