Hepatobiliary Disease USMLE Step 1 Practice Question
A 22-year-old woman presents to the emergency department 18 hours after intentional acetaminophen ingestion. She reports right upper quadrant pain, nausea, and dark urine. Vital signs: HR 104 bpm, BP 119/74 mmHg, RR 16, T 37.1°C. Laboratory findings: AST 6,400 U/L, ALT 5,900 U/L, total bilirubin 3.2 mg/dL, INR 2.3, creatinine 1.8 mg/dL. Abdominal ultrasound demonstrates hepatomegaly without cirrhosis or focal masses. She has no history of liver disease, chronic alcohol use, or hepatitis. The patient receives supportive care and N-acetylcysteine. Which hepatic acinar zone is most vulnerable to acetaminophen-induced hepatotoxicity?
Answer choices
- AZone 1 hepatocytes adjacent to the portal triad, which have high metabolic activity
- BZone 2 midzonal hepatocytes, which express intermediate levels of cytochrome P450
- CZone 3 pericentral hepatocytes, which have highest expression of CYP2E1 and low antioxidant reservesCorrect answer
- DHepatic stellate cells throughout all zones, which activate in response to oxidative stress
- EKupffer cells and sinusoidal macrophages, which are the primary targets of NAPQI
- FBile duct epithelium and cholangiocytes, which concentrate acetaminophen metabolites
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