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RD7.4 | Imaging in Surgery — Graded Quiz
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A 35-year-old man fell from a ladder and meets a high-risk criterion on the Canadian CT Head Rule (GCS less than 15 at 2 hours, two episodes of vomiting). Which single statement about imaging in head injury is correct?
Correct. NCCT head is first-line because acute blood is hyperdense on unenhanced CT, and the scan rapidly shows haematoma, mass effect and fractures.
Use a validated rule to decide who to scan, then NCCT head first — acute blood is hyperdense without contrast.
NCCT head is the modality of choice — acute blood is hyperdense without contrast. Validated rules (Canadian CT Head Rule / NICE) decide who to scan; MRI and skull X-ray are not the acute first-line.
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A head-injury CT shows a hyperdense, crescent-shaped extra-axial collection over the left cerebral convexity that crosses the suture lines but does not cross the midline. Which lesion does this describe?
Correct. A crescentic collection that crosses sutures but not the midline is an acute subdural haematoma, usually venous from torn bridging veins.
Subdural = crescentic, crosses sutures but not the midline, venous; extradural = biconvex, does not cross sutures, arterial.
Crescentic + crosses sutures + does not cross the midline = subdural haematoma (venous, bridging veins). The biconvex collection that does not cross sutures is extradural (arterial).
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A young man involved in a high-speed collision has a GCS of 6 but his initial non-contrast CT head shows no significant haematoma or mass effect, out of proportion to his profound impairment. Which investigation best demonstrates the suspected underlying injury?
Correct. MRI is far more sensitive than CT for diffuse axonal injury, which classically causes a clinical state far worse than the CT appearances suggest.
DAI: profound deficit with a relatively normal CT — MRI is the investigation that demonstrates it.
When clinical impairment is out of proportion to a near-normal CT, suspect diffuse axonal injury — MRI is the sensitive investigation for DAI.
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A 66-year-old man has a tense, tender, irreducible right inguinal hernia with vomiting and distension and is clearly strangulated on examination. After starting resuscitation, what is the correct management approach regarding imaging?
Correct. An obviously strangulated hernia is a surgical emergency — resuscitate and operate. Confirmatory imaging is reserved for equivocal cases and must not delay surgery.
Strangulation is a clinical diagnosis; resuscitate then operate. Imaging confirms equivocal cases only and must not delay surgery.
An obvious strangulated hernia goes to theatre after resuscitation. Do not delay for imaging, do not use barium, and do not forcefully reduce potentially ischaemic bowel.
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In an equivocal case of suspected strangulated hernia, a contrast-enhanced CT is obtained. Which combination of findings best indicates a closed-loop, ischaemic (strangulated) segment?
Correct. Wall thickening, absent/poor enhancement (ischaemia), a closed loop and free fluid together indicate a strangulated segment needing emergency operation.
CT signs of strangulation: bowel-wall thickening, absent/poor wall enhancement, closed-loop configuration, free fluid.
Strangulation on CT = wall thickening + absent/poor enhancement (ischaemia) + closed loop + free fluid. Normally enhancing thin wall or a fat-only sac argues against it.
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A 28-year-old woman who is 18 weeks pregnant has right iliac fossa pain suspicious of appendicitis, but a graded-compression ultrasound is inconclusive. Which is the most appropriate next imaging investigation?
Correct. In pregnancy, when ultrasound is inconclusive, MRI is the next investigation because it avoids ionising radiation while giving good diagnostic accuracy.
Appendicitis modality by population: USG first (children/young/pregnant); CT for adults/obese/equivocal; MRI in pregnancy when USG is inconclusive.
In pregnancy with an inconclusive USG, MRI is preferred next — it avoids the ionising radiation of CT. CT, plain films and barium expose the fetus to radiation or are unhelpful.
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A 72-year-old man presents with abdominal distension, absolute constipation and colicky pain. The abdominal X-ray shows peripherally placed dilated loops with haustra that do not cross the full width of the lumen, and the caecum measures 10 cm. Which is the most likely diagnosis?
Correct. Peripheral dilated loops with haustra (not crossing the full lumen width) and a caecum greater than 9 cm indicate large-bowel obstruction.
LBO: peripheral loops, haustra not crossing full width, caecum greater than 9 cm. SBO: central loops, valvulae conniventes crossing full width, calibre greater than 3 cm.
Peripheral loops + haustra (partial folds) + caecum greater than 9 cm = large-bowel obstruction. SBO has central loops with valvulae conniventes crossing the full width and calibre greater than 3 cm.
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A patient with intestinal obstruction has been confirmed on plain film, but the surgeon wants to identify the level, cause, and whether there is a closed loop or ischaemia. Which single statement is correct?
Correct. After the plain film confirms obstruction, CT is the comprehensive study that maps level and cause and detects closed-loop and ischaemia; barium is avoided when perforation is possible.
Erect/supine AXR first to confirm; CT next to map level, cause, closed-loop and ischaemia. Avoid barium if perforation is possible.
CT is the comprehensive next study for level, cause, closed-loop and ischaemia. Barium is contraindicated when perforation is possible; ultrasound and MRI are not the emergency mapping tools here.
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