In closed loop bowel obstruction, which pathophysiological feature distinguishes it from simple obstruction and makes it a surgical emergency?

• A Only one obstruction point with distal collapse and proximal dilation causing vomiting
• B Obstruction of large bowel only with competent ileocaecal valve; the mechanism is the same as simple obstruction
• C Closed loop obstruction causes volvulus only in the sigmoid colon
• D Obstruction at two points with an isolated loop trapped between them; intraluminal pressure rises rapidly causing mural ischaemia, perforation, and peritonitis independent of the proximal bowel decompression ✓

Explanation

Closed loop obstruction occurs when a segment of bowel is blocked at two points (e.g., both limbs of a volvulus, internal herniation, or adhesive band trapping a loop). This creates an isolated closed segment where intraluminal pressure rises independently of proximal decompression, rapidly causing bowel wall ischaemia, bacterial translocation, full-thickness infarction, and perforation within hours. This distinguishes it from simple obstruction where proximal decompression (NG tube, IV fluids) can temporise. CT showing a 'whirl sign' or a U-shaped dilated loop with convergent mesenteric vessels indicates closed loop obstruction requiring emergency surgery.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.