Hepatopulmonary syndrome results from the formation of microscopic intrapulmonary arteriovenous dilations in patients with chronic liver disease Cirrhosis Cirrhosis is a late stage of hepatic fibrosis that has resulted in widespread distortion of normal hepatic architecture. Cirrhosis is characterized by regenerative nodules surrounded by dense... read more typically when complicated by portal hypertension. The mechanism is unknown but is thought to be due to increased hepatic production or decreased hepatic clearance of vasodilators. The vascular dilations cause overperfusion relative to ventilation, leading to hypoxemia, particularly because patients have an increased cardiac output resulting from systemic vasodilation.
Hepatopulmonary syndrome is associated with reduced levels of bone morphogenetic protein 9 (BMP9) and BMP10 level when compared to control patients with advanced liver disease without hepatopulmonary syndrome. Lower BMP9 levels were further associated with more severe hepatopulmonary syndrome ( 1 General reference Hepatopulmonary syndrome is hypoxemia caused by pulmonary microvascular vasodilation in patients with portal hypertension; dyspnea and hypoxemia are worse when the patient is upright. Hepatopulmonary... read more ).
Because the lesions frequently are more numerous at the lung bases, hepatopulmonary syndrome can cause platypnea (dyspnea) and orthodeoxia (hypoxemia), which occur when the patient is seated or standing and are relieved by recumbency. Most patients also have characteristic findings of chronic liver disease, such as spider angiomas Nevus Araneus Nevus araneus is a bright red, faintly pulsatile vascular lesion consisting of a central arteriole with slender projections resembling spider legs. Nevus araneus lesions are acquired. One lesion... read more . About 20% of patients present with pulmonary symptoms alone.
Diagnosis of Hepatopulmonary Syndrome
Contrast echocardiography and sometimes other imaging
Hepatopulmonary syndrome should be suspected in patients with known liver disease who report dyspnea (particularly platypnea). Patients with such symptoms should have pulse oximetry. If the symptoms are severe (eg, dyspnea at rest), arterial blood gasses should be measured with the patient breathing room air and 100% oxygen to determine shunt fraction.
Pearls & Pitfalls
A useful diagnostic test is contrast echocardiography Methodology . Intravenous microbubbles from agitated saline that are normally trapped in the pulmonary capillaries rapidly (ie, within 7 heartbeats) traverse the lung and appear in the left atrium. Similarly, IV technetium-99m–labeled albumin may traverse the lungs and appear in the kidneys and brain. Pulmonary angiography Angiography Angiography is sometimes called conventional angiography to distinguish it from CT angiography (CTA) and magnetic resonance angiography (MRA). Angiography provides detailed images of blood vessels... read more may reveal a diffusely fine or blotchy vascular configuration. Angiography is generally not needed unless thromboembolism is suspected.
Treatment of Hepatopulmonary Syndrome
The main treatment is supplemental oxygen for symptoms. Other therapies, such as somatostatin to inhibit vasodilation, are of modest benefit in only some patients. Coil embolization is virtually impossible because of the number and size of the lesions. Inhaled nitric oxide synthesis inhibitors may be a future treatment option. Hepatopulmonary syndrome may regress after liver transplantation Liver Transplantation Liver transplantation is the 2nd most common type of solid organ transplantation. (See also Overview of Transplantation.) Indications for liver transplantation include Cirrhosis (70% of transplantations... read more or if the underlying liver disease subsides. Prognosis is poor without treatment (survival < 2 years).
Patients with hepatopulmonary syndrome tend to have findings of chronic liver disease and may have platypnea.
If the diagnosis is suspected, do pulse oximetry and consider arterial blood gas measurement and imaging (eg, contrast echocardiography).
Treat with supplemental oxygen.