Nitric oxide and liver disease.

Nitric oxide is a highly reactive, diffusible gas that is produced by many tissues, and it exerts a range of physiological and pathophysiological effects. The liver is one organ clearly influenced by nitric oxide, and acute versus chronic exposure to this substance has been associated with distinct patterns of liver disease. Bacterial infections, including the sepsis syndrome, acutely increase nitric oxide systemically and may lead to acute hepatic dysfunction. We review etiology, diagnosis, and treatment of cholestasis associated with these infections, because this condition in particular has been linked to nitric oxide. Chronic increases in nitric oxide may cause the hyperdynamic circulation seen in cirrhosis and portal hypertension. Therefore, we also review etiology, diagnosis, and treatment of the hepatorenal and hepatopulmonary syndromes, because both these syndromes occur in end-stage liver disease, and they may be linked to nitric oxide as well. An appreciation of nitric oxide and its evolving role in hepatology may be important to understand the pathogenesis of and treatment strategies for these different types of liver disease.