A 45-year-old woman undergoes triphasic CT abdomen for incidental right upper quadrant ultrasound finding. The lesion demonstrates the imaging feature marked **A** in the diagram — peripheral nodular discontinuous enhancement that is isodense to the aorta during the arterial phase. Which of the following best explains the pathophysiologic basis for this enhancement pattern?
A. Rapid arterial inflow into large vascular spaces lined by flat endothelium, with initial peripheral filling from feeding arteries
B. Delayed enhancement from collateral arterial supply in a cirrhotic liver with portal hypertension
C. Homogeneous arterial enhancement due to a central feeding artery with a fibrous scar
D. Washout of contrast into the portal venous system due to hepatocellular uptake and excretion
Explanation
Why "Rapid arterial inflow into large vascular spaces lined by flat endothelium, with initial peripheral filling from feeding arteries" is right
Hepatic cavernous hemangioma is the most common benign liver tumor (1–5% prevalence), consisting histologically of large vascular spaces lined by flat endothelium separated by fibrous septa. The peripheral nodular enhancement pattern seen during the arterial phase (marked A) reflects the rapid arterial inflow into these large vascular cavities from peripheral feeding arteries. This enhancement is isodense to the aorta because it represents true arterial phase blood pooling. The classic "fill-in pattern" — peripheral nodular enhancement in arterial phase followed by centripetal progression in portal venous and delayed phases — is highly specific for hemangioma and is the diagnostic hallmark on triphasic CT (Harrison's 21e Ch 348; AJR 2014).
Why each distractor is wrong
Homogeneous arterial enhancement due to a central feeding artery with a fibrous scar: This describes focal nodular hyperplasia (FNH), which shows homogeneous enhancement and a central scar, not the discontinuous peripheral nodular pattern of hemangioma.
Washout of contrast into the portal venous system due to hepatocellular uptake and excretion: This describes hepatocellular carcinoma (HCC), which shows arterial phase enhancement followed by washout in the portal venous phase — the opposite of the progressive centripetal fill-in seen in hemangioma.
Delayed enhancement from collateral arterial supply in a cirrhotic liver with portal hypertension: This is not the mechanism of hemangioma enhancement; hemangiomas occur in non-cirrhotic livers and are not dependent on portal hypertension or collateral circulation.
High-YieldNEET PG
The peripheral nodular discontinuous enhancement isodense to aorta in the arterial phase, followed by progressive centripetal fill-in, is pathognomonic for cavernous hemangioma and obviates the need for biopsy.
Harrison's 21e Ch 348; AJR 2014 Imaging of Hepatic Lesions
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