Hepatopulmonary Syndrome (Adult)

Hepatopulmonary syndrome is defined by the triad of: (1) chronic liver disease and/or portal hypertension; (2) increased alveolar-arterial oxygen gradient (A-a gradient ≥15 mmHg or ≥20 mmHg if age >64 years) on room air; and (3) evidence of intrapulmonary vascular dilatation (IPVD) demonstrated by contrast-enhanced echocardiography. Pathogenesis involves nitric oxide-mediated vasodilatation of pulmonary precapillary and capillary vessels, creating diffusion-perfusion impairment, ventilation-perfusion mismatch, and intrapulmonary right-to-left shunt.

Clinical features include progressive dyspnea (especially platypnea: worsening dyspnea upright and improving supine, due to shunt redistribution; and orthodeoxia: O2 desaturation upright and improvement supine), digital clubbing, cyanosis, and spider telangiectasias. Disease severity classified by PaO2: mild (≥80), moderate (60-79), severe (50-59), very severe (<50 mmHg). Prevalence in cirrhosis is 5-32%, with worse survival than equivalent cirrhosis without HPS.

Diagnosis requires contrast-enhanced echocardiography (transthoracic with agitated saline) showing delayed appearance of bubbles in left atrium 3-6 cardiac cycles after right atrium (transpulmonary passage indicating IPVD). Macroaggregated albumin lung-brain scan can quantify shunt fraction. Treatment: liver transplantation is the only curative therapy; HPS is now an indication for MELD exception score (PaO2 <60 mmHg). Supplemental oxygen used as bridge to transplant. Avoid pharmacologic therapies (no proven benefit). Post-transplant resolution occurs in most cases over months.