MCQ – 71135

An 80-year-old man presented with colicky abdominal pain, constipation for three days, and repeated vomiting for 1 day. Physical examination showed a distended abdomen with hyperactive bowel sounds. No abdominal mass or organomegaly was detected. Laboratory investigations were unremarkable. A supine Abdominal Xray was performed as an initial investigation.What can be the most probable diagnosis?

A.	Small Bowel Obstruction
B.	Large Bowel Obstruction
C.	Perforated Peptic Ulceration
D.	Acute Appendicitis

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Correct Answer � B Explanation

Ans:B.)Large Bowel Obstruction.

Image shows:

• Supine abdominal radiograph showing gas-filled dilated proximal large bowel and collapsed distal large bowel suggestive of mechanical large bowel obstruction. 
• Gas-filled dilated bowel in the periphery of abdomen (‘picture framing’) – representing the location of the caecum, ascending, transverse and descending colon.
•  Note the prominent haustra (arrows) – the widely spaced incomplete bands along the walls of the dilated bowel and absence of gas in the rectum.

MECHANICAL LARGE BOWEL OBSTRUCTION

• Dilatation of large bowel >5.5 cm is the hallmark of large bowel obstruction. Once this is diagnosed, the cause and its location requires further investigation.
• Colonoscopy and barium enema are relatively contra-indicated in acute obstruction for fear of bowel perforation. A water soluble contrast enema or CT abdomen are safe alternatives.
• There are many causes of large bowel obstruction and a simple way to classify them is by location:
  • 1. Intra-luminal: e.g. faecal impaction, gallstone, intussusception
  • 2. Mural: e.g. neoplasm, infection (parasites), inflammatory bowel disease
  • 3. Extrinsic: e.g. adjacent neoplasm (by compression or invasion), adjacent abscess, endometriosis
• In an elderly patient the most common cause is colonic carcinoma.