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Pathology · Haemodynamics: pulmonary infarct
Sample itemA 55-year-old dies after a pulmonary embolism that occluded a peripheral branch. At autopsy, the lung shows a wedge-shaped, dark red lesion with its base at the pleura. Why is this infarct red and not pale?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
C. Dual blood supply and loose spongy tissue allow haemorrhage
Lung infarcts are red (haemorrhagic) because the bronchial circulation supplies blood to the infarct and spongy tissue lets it collect. Solid organs with single supply and dense stroma, such as kidney, give pale infarcts.
Option by option
A. Absence of collateral supply
Absent collateral supply produces a pale infarct, the opposite picture.
B. Rapid reperfusion of the occluded artery
Reperfusion occurs in some infarcts, but this is not the main reason for lung haemorrhage.
C. Dual blood supply and loose spongy tissue allow haemorrhage (correct)
Correct. Bronchial collateral blood leaks into loose lung tissue, giving a haemorrhagic infarct.
D. Dense stroma preventing blood seepage
Dense stroma limits seepage of blood and is a feature of pale infarcts.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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