Hepatopulmonary syndrome

[Mark Zuckerberg]

Hepatopulmonary syndrome is hypoxemia caused by pulmonary microvascular vasodilation in patients with portal hypertension; dyspnea and hypoxemia are worse when the patient is upright.
Hepatopulmonary syndrome results from the formation of microscopic intrapulmonary arteriovenous dilations in patients with chronic liver disease typically when complicated by portal hypertension. The mechanism is unknown but is thought to be due to increased hepatic production or decreased hepatic clearance of vasodilators. The vascular dilations cause overperfusion relative to ventilation, leading to hypoxemia, particularly because patients have an increased cardiac output resulting from systemic vasodilation.
Hepatopulmonary syndrome is associated with reduced levels of bone morphogenetic protein 9 (BMP9) and BMP10 level when compared to control patients with advanced liver disease without hepatopulmonary syndrome. Lower BMP9 levels were further associated with more severe hepatopulmonary syndrome (1).
Because the lesions frequently are more numerous at the lung bases, hepatopulmonary syndrome can cause platypnea (dyspnea) and orthodeoxia (hypoxemia), which occur when the patient is seated or standing and are relieved by recumbency. Most patients also have characteristic findings of chronic liver disease, such as spider angiomas. About 20% of patients present with pulmonary symptoms alone.