Surgery MCQs Q41

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GENERAL SURGERY • OBSTRUCTION

A patient presents with features of intestinal obstruction. Imaging suggests a closed-loop obstruction, raising concern for ischemia and perforation.

Which of the following statements regarding closed-loop intestinal obstruction is correct?

A Not seen in sigmoid volvulus

B Seen in carcinoma of splenic flexure with competent ileocecal valve

C Seen in carcinoma of hepatic flexure with incompetent ileocecal valve

D Cannot cause perforation

E Should be treated as non-urgent surgery

The correct answer is Seen in carcinoma of splenic flexure with competent ileocecal valve.

Decoding the Stem

1

CLUE "Closed-loop obstruction"

TRANSLATION Bowel segment occluded at two points → high risk of strangulation and ischemia.

Detailed Explanation

✅ Correct Option (Closed Loop Mechanism): Closed-loop obstruction occurs when a segment of bowel is obstructed at two distinct points. In the colon, this happens when an obstructing lesion (like a carcinoma of the splenic flexure) blocks the distal end, while a competent ileocecal valve blocks the proximal end. This turns the segment into a closed system.

Pathophysiology and Risks:

→ Competent Valve: Prevents decompression of the colon into the small bowel, leading to rapid increase in pressure.

→ Risk of Perforation: According to Laplace's Law, the cecum is at the highest risk of perforation because it has the largest diameter.

→ Strangulation: Rapid distension compromises intramural blood flow, leading to ischemia, gangrene, and eventual perforation.

❌ Why other options are incorrect:

→ Sigmoid Volvulus: This is a classic example of closed-loop obstruction as the twist occludes the loop at two points (entry and exit).

→ Incompetent Ileocecal Valve: If the valve is incompetent, the colonic pressure is relieved as contents flow back into the small bowel, transforming a closed loop into an open loop obstruction.

→ Non-urgent surgery: Closed-loop obstruction is a surgical emergency due to the high risk of gangrene and perforation.

🧠 High-Yield Pearls

✔ Closed loop = Two-point obstruction (e.g., volvulus, competent IC valve).

✔ High-risk condition: Rapid onset of ischemia and perforation.

✔ Cecum: Most common site of perforation in colonic closed-loop cases.

Integrated Clinical Questions

1. Most common site of perforation?

→ Cecum (due to maximum distension/Laplace's Law).

2. Classic causes of closed-loop obstruction?

→ Volvulus, internal hernias, and obstructing tumor with a competent ileocecal valve.

3. Radiological sign?

→ Massively dilated bowel loop with little or no gas distally (e.g., "coffee bean" sign in sigmoid volvulus).

4. Why is it dangerous?

→ Intraluminal pressure exceeds capillary perfusion pressure → Compromised blood supply → Gangrene.

5. Management?

→ Urgent surgical intervention (Laparotomy).

⚡ Exam Pearls

• • Sigmoid volvulus = Classic closed loop (don't fall for the "not seen" trap).
• • Competent ileocecal valve = Key pathophysiological concept.
• • Closed loop = Surgical emergency, not elective or non-urgent.

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