Wilkie's syndrome, also known as superior mesenteric artery (SMA) syndrome, is caused by compression of the third part of the duodenum (the first part of the small intestine) between the superior mesenteric artery (SMA) and the aorta.
Understanding the Mechanics of Wilkie's Syndrome
Here's a breakdown of the contributing factors:
- The Superior Mesenteric Artery (SMA): This major artery branches off the aorta and supplies blood to the small intestine.
- The Aorta: This is the main artery carrying blood away from the heart.
- The Duodenum: The first part of the small intestine.
Normally, there's enough space between the SMA and the aorta for the duodenum to pass without obstruction. However, in Wilkie's syndrome, this space narrows. This narrowing can result from several factors:
- Decreased Angle Between the SMA and Aorta: Typically, the SMA branches from the aorta at an angle of around 45 degrees. In people with Wilkie's syndrome, this angle can decrease to as little as 6-16 degrees. This sharp angle pinches the duodenum.
- Loss of Retroperitoneal Fat: The retroperitoneal fat pad cushions and supports the SMA, maintaining a sufficient angle. Rapid weight loss (e.g., from malnutrition, surgery, or illness) can diminish this fat pad, leading to a decreased angle and compression.
- Anatomical Abnormalities: Some individuals may have congenital or acquired anatomical abnormalities that predispose them to SMA compression. Examples include a high insertion of the duodenum, low origin of the SMA, or an abnormally short ligament of Treitz.
- Skeletal Abnormalities: Conditions like scoliosis or lordosis can alter the relationship between the SMA and the aorta, increasing the risk of duodenal compression.
- Prolonged Bed Rest/Casting: Immobilization can also contribute by weakening the abdominal muscles, decreasing the distance between the SMA and the aorta.
Risk Factors for Wilkie's Syndrome
While the exact cause involves duodenal compression by the SMA, several factors increase the risk:
- Rapid Weight Loss: Especially in conditions like anorexia nervosa, cancer, or malabsorption syndromes.
- Surgery: Spinal surgery, corrective scoliosis surgery, or any major abdominal surgery.
- Trauma: Injuries that affect the spine or abdomen.
- Prolonged Bed Rest: Immobilization can contribute to muscle atrophy and changes in abdominal anatomy.
- Malnutrition: Leading to loss of the retroperitoneal fat pad.
- Congenital Factors: Some individuals may be born with a predisposition due to anatomical variations.
In Summary
Wilkie's syndrome arises from the compression of the duodenum between the SMA and the aorta, typically due to a decreased angle between these arteries or loss of the retroperitoneal fat pad. This compression leads to partial or complete duodenal obstruction.
