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RD7.4 | Imaging in Surgery — Practice Quiz
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A 24-year-old man is brought to casualty 1 hour after a road traffic accident. He had a brief loss of consciousness, now has a GCS of 14, has vomited twice, and there is bruising over the right temporal region. He meets a criterion for imaging on the Canadian CT Head Rule. Which imaging investigation is the modality of choice as the first scan?
Correct. In acute head trauma, non-contrast CT head is the undisputed modality of choice — it is fast, available, and excellent at detecting acute blood, fractures, and mass effect, which directly drive the surgical decision.
NCCT head is first-line in acute head injury because acute blood is hyperdense without contrast and CT rapidly shows haematoma, mass effect and fractures — the findings that decide whether the patient goes to theatre.
In acute head injury the first scan is non-contrast CT. Contrast adds nothing acutely (fresh blood is already hyperdense), MRI is slower and less available for the unstable trauma patient, and plain skull films do not show the intracranial injury that determines management.
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A head-injury CT shows a hyperdense, biconvex (lens-shaped) extra-axial collection over the right temporoparietal region that does not cross the cranial sutures, with associated mass effect. Which diagnosis do these appearances best describe?
Correct. A biconvex (lentiform) hyperdense collection that does NOT cross sutures is the classic extradural haematoma, typically arterial from the middle meningeal artery; the dura's firm attachment at sutures limits its spread.
Shape rule: extradural = biconvex/lentiform, does NOT cross sutures (arterial, middle meningeal artery); subdural = crescentic, crosses sutures but not the midline (venous, bridging veins).
The biconvex shape that respects (does not cross) the suture lines is the signature of an extradural haematoma. A subdural haematoma is crescentic and crosses sutures but not the midline.
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A 70-year-old man presents with a tense, tender, irreducible right inguinal hernia, abdominal distension and vomiting. A contrast-enhanced CT is performed. Which CT finding most specifically indicates strangulation (bowel ischaemia) within the hernia and mandates emergency surgery?
Correct. Absent or reduced bowel-wall enhancement (with wall thickening, closed-loop configuration and free fluid) indicates compromised perfusion — ischaemic bowel that may be dead and requires emergency operation.
On CT, strangulation is suggested by bowel-wall thickening, absent/poor wall enhancement (ischaemia), a closed-loop configuration and free fluid — but remember strangulation is fundamentally a CLINICAL diagnosis and an obvious case should not wait for a scan.
The key ischaemia sign is absent/poor wall enhancement, usually with wall thickening, a closed loop and free fluid. Normally enhancing, reducible loops or a fat-only sac do not indicate strangulation.
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A surgeon asks for the single most important principle in managing an obviously strangulated hernia — a tense, tender, irreducible hernia with bowel obstruction. Which statement is correct regarding the role of imaging?
Correct. Strangulation is a clinical diagnosis. In an obvious case the patient is resuscitated and taken to theatre; imaging is reserved for equivocal cases and must never delay surgery when ischaemia is clinically evident.
A tense, tender, irreducible hernia with obstruction goes to theatre after resuscitation — do not let a confirmatory scan delay the operation in an obvious case.
An obviously strangulated hernia is a clinical diagnosis and surgical emergency — resuscitate and operate. CT is for confirmation in equivocal cases, not a mandatory pre-op step; barium and plain X-ray do not confirm or exclude ischaemia reliably.
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An 8-year-old boy has migratory right iliac fossa pain, anorexia and low-grade fever; appendicitis is suspected but the examination is equivocal. Which imaging investigation is the appropriate first-line choice in this child?
Correct. In children, young/thin adults and pregnancy, ultrasound is first-line because it avoids radiation; CT is reserved for adults, the obese or equivocal scans, and MRI for pregnancy when USG is inconclusive.
Match the modality to the patient: USG first in children, young/thin adults and pregnancy (no radiation); CT in adults, the obese and equivocal cases; MRI in pregnancy when USG is inconclusive.
Ultrasound is first-line for appendicitis in children to avoid ionising radiation. CT (radiation) is reserved for adults/obese/equivocal cases; plain films and barium have no role in diagnosing acute appendicitis.
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An ultrasound performed for suspected appendicitis demonstrates a non-compressible, blind-ending tubular structure in the right iliac fossa measuring 8 mm in diameter, with an echogenic appendicolith and surrounding fat changes. Which interpretation is correct?
Correct. A non-compressible, blind-ending tube with diameter greater than 6 mm, often with an appendicolith and a target sign, are the classic ultrasound features of acute appendicitis.
Sonographic appendicitis: non-compressible, blind-ending tube greater than 6 mm, appendicolith, target sign in cross-section, and inflammatory fat/free-fluid changes.
A non-compressible blind-ending tube greater than 6 mm with an appendicolith is diagnostic of acute appendicitis — a normal appendix is compressible and 6 mm or less. These signs are not those of bowel obstruction or a hernia.
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A 60-year-old woman with previous appendicectomy and caesarean presents with colicky central abdominal pain, vomiting and distension. The erect abdominal X-ray shows multiple central dilated loops with valvulae conniventes crossing the full width of the lumen and several air-fluid levels. Which is the most likely diagnosis?
Correct. Centrally placed dilated loops with valvulae conniventes that cross the full lumen width, plus air-fluid levels, indicate small-bowel obstruction — and adhesions from previous surgery are the commonest cause.
SBO: central dilated loops, valvulae conniventes crossing the full lumen width, calibre greater than 3 cm. LBO: peripheral loops, haustra not crossing full width, caecum greater than 9 cm. Adhesions are the commonest SBO cause.
Valvulae conniventes crossing the full width of the lumen in central loops indicate small bowel. Large-bowel obstruction shows peripheral loops with haustra that do NOT cross the full width. Adhesions are the commonest cause of SBO.
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While reviewing imaging for a patient with suspected intestinal obstruction, you are asked which finding indicates perforation and which investigation is contraindicated when perforation is possible. Which option is correct?
Correct. Free intraperitoneal (pneumoperitoneum) air signifies perforation. Barium is contraindicated if perforation is possible because leaked barium causes severe chemical peritonitis; a water-soluble contrast or CT is used instead.
Free air on imaging means perforation. If perforation is possible, avoid barium (risk of barium peritonitis) — use water-soluble contrast or CT, which also maps level, cause, closed-loop and ischaemia.
Free intraperitoneal air = perforation. Barium is contraindicated when perforation is possible (barium peritonitis); CT is the comprehensive study for level, cause, closed-loop and ischaemia and is not contraindicated.
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