Expansion
A one-way valve between ileum and caecum; a competent valve creates a closed loop
Expansion
The ileocaecal valve consists of two lips of ileal mucosa projecting into the caecum. It limits reflux of colonic contents into the ileum, helping maintain the relatively sterile small bowel.
In large bowel obstruction, its competence determines the picture:
- Competent valve - no decompression backwards into the ileum, so a closed loop forms between the valve and the obstruction. Pressure rises rapidly, small bowel appears normal on radiography, and the risk is caecal perforation
- Incompetent valve - the colon decompresses into the small bowel, giving small bowel dilatation and vomiting, and buying time
The caecum is the site of perforation because of the law of Laplace: for a given pressure, wall tension is proportional to radius, and the caecum has the largest diameter. A caecal diameter above 9 cm is the accepted threshold for concern.