see also:

• the patient with acute abdominal pain in the ED
• small bowel obstruction

• obstruction of the large bowel results in proximal dilatation (and potentially dilatation of small bowel) with inability to pass faeces or flatus.
• excessive distension may result in perforation and peritonitis
• closed loop obstructions may strangulate leading to infarction and perforation.
• true mechanical obstruction must be differentiated from pseudo-obstruction which may result from:
  • neurologic conditions
  • diabetes
  • hypothyroidism
  • scleroderma
  • amyloidosis
  • chronic renal failure
  • congestive cardiac failure
  • electrolyte imbalances

• neoplasms (60%) esp. colonic
• diverticulitis (10-20%)
• volvulus (5-15%) - sigmoid volvulus more common than caecal volvulus
• uncommonly, faecal impaction, inflammatory bowel disease (IBD), ischaemic colitis, radiation colitis

• dilated colon, especially a dilated caecum
  • caecum is normally < 9cm wide, and becomes at risk of perforation if > 12cm
  • remainder of colon is normally < 6cm wide, and becomes at risk of perforation if > 9cm
• small bowel dilatation (in 25% of cases due to reflux through the ileocaecal valve)
• air-fluid levels in the colon, especially distal to the hepatic flexure
• see also small bowel obstruction and ischaemic colitis