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.
Patients can presents with signs/symptoms of bowel obstruction including crampy abdominal pain, vomiting, abdominal distension and high pitched or absent bowel sounds.
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 cecal). In closed loop obstruction, there is a high risk of strangulation and bowel infarction (10-35%).
Some publications suggest two obstructive features combine and are responsible for the obstruction 15.
closed loop syndrome
- incarcerated loop (closed loop) continues to secrete distends, inducing parietal vascular constraints (normally it does contains very little or no gas with the exception of when it involves the colon (fermentation gases).
- induced extravasation of blood and plasma from venous stasis both in the excluded loop and in the adjacent mesentery, increasing the intestinal distension.
- segment of intestine upstream from proximal point of obstruction progressively distends to the stomach.
- slower than in case of a incarcerated segment.
CT findings of a closed-loop obstruction depend in part on the orientation of the loop relative to the plane of imaging. Some or all of the following signs may be demonstrated on CT:
- marked distension of a segment of small bowel
- >3cm is the generally accepted caliber for distended small bowel (see the 3-6-9 rule)
- radially distributed, C or U-shaped small bowel loops
- "double beak sign": 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 ischemia
Treatment and prognosis
Risk of strangulation leads to high morbidity and mortality in closed loop bowel obstructions. Immediate surgical intervention is required.
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