Surgery — Intestinal Obstruction and Colorectal Disease, NMC MBBS licence examination syllabus (Nepal Medical Council).
NMC-style practice questions written for this site. They are not past questions, and no past paper has been reproduced.
1. Name the four cardinal features of intestinal obstruction, and explain what "absolute" adds to constipation.
Answer: Colicky abdominal pain, vomiting, distension and absolute constipation. Absolute means the patient passes neither stool nor flatus — a patient still passing flatus has something getting past the blockage, so the obstruction is incomplete.
2. Why is vomiting early in high obstruction and late in low obstruction?
Answer: Because of the length of bowel above the block. A short proximal column fills and empties upwards quickly, so vomiting comes early; a long column takes time to fill before contents back up far enough to be vomited.
3. An obstructed patient's colicky pain becomes constant, with guarding and a rising pulse. What has changed and what should happen?
Answer: These suggest strangulation — the blood supply is compromised and the bowel is becoming ischaemic. Colic reflects gut contracting; constant pain reflects gut dying. Conservative management is no longer appropriate and the patient needs surgery, because every hour costs bowel that would have been viable.
4. A patient presents with obstruction and has never had abdominal surgery. What must be examined, and why?
Answer: The hernial orifices. Without previous surgery adhesions are unlikely, making an obstructed hernia the commonest cause — and it is diagnosed by looking, needs no imaging, and is treatable. It is the step most often skipped.
5. Why does a right-sided colonic cancer present later than a left-sided one?
Answer: The right colon is wide and its contents liquid, so a tumour can grow substantially before obstructing anything, and its bleeding is occult. The left colon is narrower with formed stool, so a smaller tumour produces a change in bowel habit, visible bleeding or obstruction much sooner.
6. A 68-year-old is found to have iron-deficiency anaemia with no obvious source of bleeding. Why is treating with iron alone inadequate?
Answer: Because iron deficiency in an older patient is a colonic lesion until proven otherwise — a right-sided tumour bleeds slowly and invisibly, and anaemia may be its only sign. Correcting the haemoglobin treats the consequence and leaves a potentially curable cancer undiagnosed.
7. Why are patients with intestinal obstruction usually much more dehydrated than they appear?
Answer: Because large volumes are lost into the bowel lumen itself as well as through vomiting. That fluid is still inside the body but no longer in the circulation, so the usual estimate based on visible losses substantially underestimates the deficit.
8. Faeculent vomiting is described in a patient with obstruction. Does this indicate perforation?
Answer: No. Faeculent vomit is stagnant small bowel content that bacteria have acted on over time, so it indicates the duration and the low level of the obstruction. It is not stool, and it does not by itself imply that the bowel has perforated.
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