Closed loop obstruction is a specific type of small bowel obstruction in which two points along the course of a bowel are obstructed at a single location thus forming a closed loop. Closed loop usually rotates around its axis, forming a small intestinal volvulus.
This is usually secondary to adhesions, a twist of the mesentry or herniation. A similar related pathology is the large bowel volvulus (either sigmoid or caecal). In closed loop obstruction, there is a high risk of strangulation and bowel infarction (10-35%).
Some or all of the following signs may be demonstrated on CT:
- marked distension of a segment of small bowel
- radially distributed, C or U-shaped small bowel loops
- "beak sign": of the tapering bowel loops at the point of obstruction
- "whirl sign": of the tightly twisted mesentery
- two adjacent collapsed loops of bowel
- if strangulation is present, signs of bowel ischaemia
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