A 55-year-old man with known cirrhosis presents with progressive dyspnea on exertion and platypnea. Physical examination reveals clubbing and multiple spider nevi on the chest. Arterial blood gas on room air shows PaO2 of 58 mmHg with an elevated alveolar-arterial oxygen gradient. Which diagnostic test is most appropriate to confirm the suspected diagnosis?
- A Contrast-enhanced echocardiography (bubble study) ✓
- B High-resolution CT thorax
- C Pulmonary angiography
- D Ventilation-perfusion (V/Q) scan
Correct answer: A. Contrast-enhanced echocardiography (bubble study)
Explanation
This presentation is classic for hepatopulmonary syndrome (HPS): liver disease, hypoxemia with elevated B-a gradient, and signs of chronic liver disease. Contrast-enhanced echocardiography (agitated saline bubble study) is the preferred screening test. In HPS, microbubbles appear in the left atrium after 3 to 6 cardiac cycles (delayed), distinguishing intrapulmonary shunting from intracardiac shunting where they appear within 3 cycles. HRCT and V/Q scan are not diagnostic for HPS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.