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Closed loop obstruction

A 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.

Pathology

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%).

Radiographic features

CT

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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