The association of chronic liver disease with respiratory symptoms and hypoxia is well recognized. Over the last century, three pulmonary complications specific to chronic liver disease have been characterized: hepatopulmonary syndrome (HPS), portopulmonary hypertension (POPH), and hepatic hydrothorax (HH). The development of portal hypertension is fundamental in the pathogenesis of each of these disorders. HPS is the most common condition, found in 5%-30% of cirrhosis patients, manifested by abnormal oxygenation due to the development of intrapulmonary vascular dilatations. The presence of HPS increases mortality and impairs quality of life, but is reversible with liver transplantation (LT). POPH is characterized by development of pulmonary arterial hypertension in the setting of portal hypertension, and is present in 5%-10% of cirrhosis patients evaluated for LT. Screening for POPH in cirrhosis patients eligible for LT is critical since severe POPH is a relative contraindication for LT. Patients with moderate POPH, who respond adequately to medical therapy, may benefit from LT, although sufficient controlled data are lacking. HH is a transudative pleural effusion seen in 5%-10% of cirrhosis patients, in the absence of cardiopulmonary disease. Diagnosis of HH should prompt consideration for LT, which is the ultimate treatment for HH. Conservative management includes salt restriction and diuretics, with thoracentesis and transjugular intrahepatic portosystemic shunt (TIPS) as second-line therapeutic options. (HEPATOLOGY 2014;59:1627-1637
Hepatopulmonary SyndromeThe hepatopulmonary syndrome (HPS) is defined by an oxygenation defect caused by the development of intrapulmonary vascular dilatation (IPVD) in patients with either advanced liver disease and/or portal hypertension. Impaired oxygenation in HPS is reflected by a widened age-corrected alveolar-arterial oxygen gradient (P[A-a]O 2 ) on room air, with or without hypoxemia. 1 Cirrhosis, irrespective of the underlying cause, is the most common hepatic condition associated with HPS. However, HPS may also develop in noncirrhotic portal hypertension and ischemic hepatitis.2,3 HPS may occur in patients with coexisting cardiopulmonary conditions and further exacerbate existing respiratory symptoms and hypoxemia in these patients. 4
PathogenesisThe appearance of IPVD underlies the development of HPS. This vascular abnormality consists of diffuse or localized dilated abnormal pulmonary capillaries and, less commonly, pleural and pulmonary arteriovenous communications which result in impaired oxygenation of venous blood as it passes through the pulmonary circulation.5 Nitric oxide (NO), a potent vasodilator, has been linked to IPVD. Increased levels of exhaled NO derived from the lung are seen in cirrhosis patients with HPS, which normalize after liver transplantation (LT).
6Chronic common bile duct ligation in the rat results in biliary cirrhosis, and recapitulates the physiologic changes of human HPS. The majority of what is Abbreviations: ABG, arterial blood gas; ...