Portopulmonary Hypertension and Hepatopulmonary Syndrome: Contrasting Pathophysiology and Implications for Liver Transplantation

Portopulmonary hypertension (PoPH) and hepatopulmonary syndrome (HPS) present two vascular complications of portal hypertension, which make opposite extremes occur against the same pathophysiological background. In PoPH, vasoconstriction predominates, along with gradual remodeling of pulmonary arteries, while HPS develops due to pathological vasodilation and creation of intrapulmonary shunts. Even though they come about by different mechanisms, both disorders significantly affect quality of life, survival, and the possibility of liver transplant. In the early phases, in clinical practice, symptoms are mainly mild and nonspecific, and overlapping with symptoms of advanced liver disease often delays forming a diagnosis. In PoPH, elevated pressures in pulmonary arteries and increased vascular resistance are observed, while HPS exhibits arterial hypoxemia with normal or lowered pulmonary pressure. Standard diagnostic workup includes echocardiography, right-heart catheterization, and analysis of the arterial gases. In patients with severe PoPH, pronounced pulmonary hypertension can represent absolute contraindication for liver transplantation due to risk of acute right heart failure during operation. Conversely, HPS usually resolves itself after a successful transplant, which confirms that the transplant is an indication of being potentially curative. Therapeutic possibilities for both states are still limited. In PoPH, specific vasodilators and supportive measures are applied, while HPS treatment is mostly supportive, directed at maintaining oxygenation until the transplant. Future research should be focused on the development of targeted therapies that address vascular remodeling, angiogenesis, and oxidative stress, as well as on the standardization of diagnostic criteria and multicentric cooperation. This approach would facilitate earlier recognition, a precise assessment of transplantability, and a better long-term outcome for patients with portal hypertension and lung vascular complications. <b>Key Points:</b> Portopulmonary hypertension (PoPH) and hepatopulmonary syndrome (HPS) represent two opposite vascular complications of portal hypertension, posing distinct challenges for liver transplantation. This review summarizes their pathophysiology, diagnostic pathways, and therapeutic strategies, emphasizing the importance of hemodynamic profiling and multidisciplinary management to optimize transplant outcomes.