A 46-year-old man with cirrhosis reports breathlessness that is worst when lying flat and improves when sitting upright. Room air PaO2 is 68 mmHg. Chest radiograph and spirometry are normal. Which test confirms the suspected diagnosis?

• A Right heart catheterisation showing elevated pulmonary vascular resistance
• B Transjugular liver biopsy showing sinusoidal dilatation
• C CT pulmonary angiogram showing segmental filling defects
• D Contrast-enhanced transthoracic echocardiography showing delayed appearance of microbubbles in left atrium ✓

Explanation

Platypnea and orthodeoxia in cirrhosis suggest hepatopulmonary syndrome, caused by intrapulmonary vascular dilatations creating shunts. Agitated saline contrast echo is the key test: bubbles appear in the left chambers after three to six cardiac cycles, later than in cardiac shunts. Portopulmonary hypertension instead shows raised pulmonary vascular resistance, and pulmonary embolism would show filling defects rather than positional desaturation.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.