Definition: The hepatopulmonary syndrome (HPS) associates a chronic hepatic affection, hypoxemia < 70 mm Hg and pulmonary vasodilatation.
Physiopathology: The mechanisms leading to pulmonary vasodilatation are complex and unclear. There appears to be an imbalance between the vasodilatating and vasoconstricting mediators. Nitrogen monoxide and endotheline-1 are well known. Hypoxia can be explained by the association of heterogenic ventilation-perfusion, shunts (rare), and a default in "diffusion-perfusion".
Clinical aspects: In a hypoxic patient, platypnoea and orthodeoxia are characteristic of HPS. Stellar angioma associated with digital hippocratism and signs of portal hypertension are usually present.
To permit diagnosis: The air of blood gases, followed by 100% O2, standing and reclining, must be measured in all cirrhotic patients to detect hypoxemia. Contract sonography is the key diagnostic examination. Pulmonary perfusion scintigraphy establishes prognosis. Pulmonary angiography differentiates two groups of patients and, for type II patients, embolization therapy can be proposed. Preliminary data indicate that densitometry, conducted in rigorous conditions, can show pulmonary vasodilatation. Its interest must be confirmed by further studies on larger cohorts of patients.
Therapeutic possibilities: The only efficient treatment of HPS is hepatic transplant (HT). The placing of an intra-hepatic portal systemic shunt can be proposed while waiting for HT, or in certain patients not requiring HT. No medical treatment has demonstrated its efficacy, but better knowledge of the physio-pathologic mechanisms should improve this situation in the future.