The hepatopulmonary syndrome

HPS is an increasingly recognized clinical entity resulting from vasodilatation in the pulmonary microcirculation in patients with liver disease or portal hypertension: The pathogenesis of alterations in the pulmonary vascular bed in affected patients is poorly understood, though recent work in an animal model suggests that altered pulmonary expression of vasoactive mediators in the lung, including he endothelial form of nitric oxide synthase, may be important in the development of vasodilatation. Ongoing studies focused on identifying the factors involved in triggering changes in pulmonary vasoactive mediators in animal models of liver disease may provide significant insight into the pathogenesis of this syndrome and help guide future therapy. The clinical features of HPS, including exertional dyspnea, platypnea, clubbing, and the presence of spider angiomas, are important in considering the diagnosis. Prospective studies using contrast echocardiography and lung perfusion scanning have provided an appropriate diagnostic approach. The development of rational medical therapies for this syndrome awaits a more complete understanding of its pathogenesis, though liver transplantation has emerged as a useful therapy in patients with significant impairment in gas exchange. Specific contraindications to transplantation in patients with HPS have not been identified, though unique postoperative complications have been observed and may be treatable during he frequently prolonged resolution of intrapulmonary vasodilatation. Prospective studies and the development of a database of information on patients with HPS undergoing transplantation are needed to characterize the natural history of this syndrome and to identify potential prognostic features for patients being considered for transplantation.