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Large bowel obstruction (LBO) is a mechanical or functional blockage of colonic contents, leading to distension, pain, and risk of ischemia or perforation. It accounts for ~20–25% of intestinal obstructions and usually occurs in older adults.

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Etiology

Mechanical (most common):

• Malignancy (colorectal carcinoma – most common, esp. sigmoid/rectosigmoid).
• Volvulus – sigmoid (MC), cecal (less common).
• Diverticular stricture (post-inflammatory fibrosis).
• Fecal impaction.
• Benign strictures (Crohn’s, ischemic colitis, radiation).
• Herniation (internal or parastomal – rare).

Functional:

• Acute colonic pseudo-obstruction (Ogilvie syndrome).

Pathophysiology

• Distal obstruction → proximal bowel dilatation.
• Colon can dilate up to 6 cm (normal), cecum up to 9 cm before risk of perforation.
• Main risk site: cecum perforation (law of Laplace).
• Distal lesions cause marked distension, delayed vomiting.

Clinical Features