What is hepatopulmonary syndrome (HPS)?

From the Guidelines

Hepatopulmonary syndrome (HPS) is a disorder in pulmonary oxygenation, caused by intrapulmonary vasodilatation and, less commonly, by pleural and pulmonary arteriovenous communications occurring in the clinical setting of portal hypertension.

Definition and Diagnosis

• HPS is characterized by hypoxia with partial pressure of oxygen <80 mmHg or alveolar–arterial oxygen gradient ≥15 mmHg in ambient air, pulmonary vascular defect with positive findings on contrast-enhanced echocardiography, and portal hypertension, commonly in the presence of hepatic portal hypertension with underlying cirrhosis 1.
• The diagnosis of HPS can be made using contrast-enhanced echocardiography or abnormal uptake in the brain (>6%) with radioactive lung-perfusion scanning 1.
• The alveolar-arterial oxygen gradient can be calculated using the formula: PaO2 = (FIO2 [Patm–PHO] - [PaCO2/0.8]) - PaO2 1.

Clinical Features and Prevalence

• HPS is most commonly diagnosed in patients with cirrhosis and portal hypertension, but it has also been described in patients with pre-hepatic portal hypertension, venous obstruction, and acute or chronic hepatitis 1.
• The prevalence of HPS has been reported to be around 10-17% in patients with cirrhosis 1.
• HPS can lead to hypoxemia and may require oxygen therapy 1.

Treatment and Management

• Liver transplantation (LT) is the only curative treatment for HPS, as it can reverse the condition through closure of the shunts 1.
• Patients with severe HPS (PaO2 <50 mmHg and no reversibility to 100% oxygen) may have a high risk of irreversible respiratory failure and perioperative mortality 1.
• Careful management of patients with HPS is crucial, including close monitoring of oxygen levels and avoidance of right ventricular failure 1.

From the Research

Definition and Characteristics of Hepatopulmonary Syndrome (HPS)

• Hepatopulmonary syndrome (HPS) is characterized by abnormalities in blood oxygenation caused by the presence of intrapulmonary vascular dilations (IPVD) in the context of liver disease, generally at a cirrhotic stage 2.
• HPS is defined by abnormally dilated blood vessels and shunts within the lungs, leading to impaired oxygen exchange 3.
• The key pathological features of HPS include intrapulmonary angiogenesis and vascular dilations (IPVDs) 4.

Diagnosis and Prevalence of HPS

• The diagnosis of HPS requires taking an arterial blood gas sample of a seated patient with alveolar-arterial oxygen gradient (AaO2) ≥ 15 mm Hg, or ≥ 20 mm Hg in those over 64 years of age 2.
• Contrast-enhanced echocardiography is considered the primary radiological evaluation for identifying abnormal blood vessel dilations within the lungs 3.
• The prevalence of HPS varies widely due to inconsistent diagnostic criteria and a lack of standardized protocols, but it is reported to occur in 5-32% of patients with cirrhosis 5, 4.

Treatment and Prognosis of HPS

• Liver transplantation is the only established treatment option for HPS and has been shown to reverse the syndrome and improve survival rates, even in severe cases 2, 5, 3, 4, 6.
• HPS carries a significant risk of mortality before transplantation, regardless of the severity of liver disease 3.
• The adoption of the model for end-stage liver disease (MELD) standard exception policy has notably improved the results for individuals with HPS compared to the period before MELD was introduced 3, 6.