Pulmonary Vascular Complications of Liver Disease

Abstract

Hepatopulmonary syndrome and portopulmonary hypertension are two pulmonary vascular complications of liver disease. The pathophysiology underlying each disorder is distinct, but patients with either condition may be limited by dyspnea. A careful evaluation of concomitant symptoms, the physical examination, pulmonary function testing and arterial blood gas analysis, and echocardiographic, imaging, and hemodynamic studies is crucial to establishing (and distinguishing) these diagnoses. Our understanding of the pathobiology, natural history, and treatment of these disorders has advanced considerably over the past decade; however, the presence of either still increases the risk of morbidity and mortality in patients with underlying liver disease. There is no effective medical treatment for hepatopulmonary syndrome. Although liver transplantation can resolve hepatopulmonary syndrome, there appears to be worse survival even with transplantation. Liver transplantation poses a very high risk of death in those with significant portopulmonary hypertension, where targeted medical therapies may improve functional status and allow successful transplantation in a small number of select patients.Keywords: hepatopulmonary syndrome; hypertension; pulmonary; liver cirrhosis; pulmonary circulationThe pulmonary circulation may be affected by pathogenic processes arising within the liver and portal venous system. Reports of abnormalities of the pulmonary vasculature found in association with coexisting chronic liver disease were first published in the 1950s (1, 2). Hepatopulmonary syndrome (HPS) and portopulmonary hypertension (PoPH) are both associated with portal hypertension and/or liver disease and in simplest terms are related to excessive pulmonary microvascular dilation (in HPS) or vasoconstriction/vascular obstruction in pulmonary resistance vessels (in PoPH). The fact that these seemingly disparate conditions can occur within the same patient population (and even simultaneously or sequentially in the same patient) suggests the role of disease modifiers that determine the particular pulmonary vascular phenotype. These important pulmonary complications both commonly present with dyspnea, yet have unique pathophysiologies, diagnostic modalities, approaches to treatment, and distinct implications regarding liver transplantation (LT). A thorough understanding of the approach to evaluation and treatment of patients with cirrhosis and possible pulmonary vascular disease is imperative to minimize sequelae and to ensure appropriate management of the underlying liver disease.HEPATOPULMONARY SYNDROME Definition HPS is a disorder of altered gas exchange due to abnormal capillary dilatation and/or arteriovenous fistulae within the pulmonary vascular bed (3). The European Respiratory Society Task Force on Pulmonary-Hepatic Vascular Disorders has defined HPS by the presence of (1) Use of the A-a gradient criterion for abnormal gas exchange captures cases of HPS that would not otherwise meet the Pa O 2 criterion (e.g., due to cirrhosis-in...

Inflammatory bowel diseases, chronic liver diseases and the lung

“…The mechanisms of other types of PAH may not necessarily be the same as those underlying POPH [90]. Expression of prostacyclin synthase appears to be reduced within pulmonary arteries in both subsets of PAH [113], while endothelin abnormalities have been identified in iPAH and liver cirrhosis and portal hypertension [114].…”

“…There are two salient liver-induced pulmonary vascular disorders that deserve to be considered under this subheading: POPH and HPS [89][90][91][92]. Both are increasingly recognised due to the therapeutic success of liver transplants [93].…”

“…POPH is defined as a pulmonary arterial hypertension (PAH) associated with portal hypertension [90,[95][96][97]. Diagnosis of POPH is based on pulmonary haemodynamic criteria obtained via right heart catheterisation [97][98][99].…”

Coil Embolization of Pulmonary Arteries as a Palliative Treatment of Diffuse Type I Hepatopulmonary Syndrome

“…Patients may also have true anatomic shunting in the form of direct arteriovenous communications. 2,3,[8][9][10] The pathogenesis of intrapulmonary vascular dilatation is controversial; however, many theories are supported by the increased presence of vasoactive substances such as nitric oxide in patients with hepatopulmonary syndrome. 1,2,8 Some propose that there is enhanced pulmonary production of nitric oxide likely secondary to an increased presence of endothelial nitric oxide synthase and inducible nitric oxide synthase in the pulmonary vasculature.…”

Hepatopulmonary Syndrome: A Brief Review

“…Despite years of research, diagnosing HPS is still difficult due to the existence of other comorbidities and unclear clinical presentation. Moreover, the only proven therapy for HPS is liver transplantation (LT) [3,4]. Thus, early diagnosis of HPS is needed to put the patients in priority list for LT. For these reasons, a physician looking to diagnose and manage patients with HPS will need extensive knowledge and broad clinical experience.…”