Editor,—I read with interest the leading article on hepatopulmonary syndromes ((2000) Gut 46:1–4; OpenUrlCrossRefPubMedWeb of Science) . The author describes explicitly the various associations between the liver and lung disorders. Several clinical studies and autopsy findings have demonstrated a 20% higher prevalence of pulmonary hypertension in patients with advanced liver disease and portal hypertension, the histological findings of which show features similar to those seen in pulmonary hypertension from other causes.1 ,2 However, the underlying mechanism(s) responsible for pulmonary hypertension in …