Hepatopulmonary syndrome (HPS) presents with hypoxia due to pulmonary shunting through expanded blood vessels in the lungs (intrapulmonary vascular dilatations [IPVDs]), in the setting of cirrhosis, portal hypertension (even in the absence of cirrhosis), or congenital porto-systemic vascular disease. Affected patients tend to have chronic liver disease complicated by portal hypertension, although nonhepatic causes of portal hypertension can also lead to HPS. In patients with liver disease, no risks besides having portal hypertension have been implicated in causing HPS. Portal hypertension may cause the release of vasoactive agents, such as nitric oxide, which results in pulmonary vasodilation and angiogenesis. This causes hypoxemia via ventilation-perfusion mismatch and oxygen diffusion limitation.

Clinical manifestations include dyspnea, platypnea (dyspnea worsened by moving to upright position and relieved by lying flat), orthodeoxia (decrease in arterial oxygen by at least 5% when moving from supine to upright position), and nail clubbing. Patients will also have manifestations of chronic liver disease and portal hypertension (ie, spider angiomata, ascites, lower extremity edema, jaundice, asterixis, and encephalopathy).

HPS is a progressive disease, and mortality is typically linked to complications from underlying liver disease and not from hypoxic respiratory failure.