Hepatopulmonary syndrome and portopulmonary hypertension

Pulmonary vascular complications of liver disease comprise two distinct clinical entities, hepatopulmonary syndrome (HPS, microvascular dilatation and angiogenesis) and portopulmonary hypertension (POPH, vasoconstriction and remodeling in resistance vessels). These complications occur in similar pathophysiologic environments and may share pathogenic mechanisms. HPS is found in 15-30% of patients with cirrhosis and its presence increases mortality and the risks of liver transplantation, particularly when hypoxemia is present. No medical therapies are available, although liver transplantation is effective in reversing the syndrome. There are no reliable clinical predictors for HPS and no established screening guidelines. However, pulse oximetry based screening protocols are useful for identifying hypoxemic patients and targeting subsequent evaluation for HPS. POPH is found in 1-8% of patients undergoing liver transplantation evaluation. The presence of moderate to severe POPH significantly increases peri-operative transplant mortality. Trans-thoracic echocardiography is recommended for screening and right heart catheterization is required to establish the diagnosis. Medical therapies are increasingly effective in POPH and may result in better peri-operative outcomes. However, whether liver transplantation will improve or reverse underlying POPH remains undefined.