Hepatopulmonary syndrome and extrahepatic vascular abnormalities

Abstract

This report describes the unique development of pulmonary vascular dilatation and hypoxemia associated with portosystemic shunt in a pediatric liver transplant recipient. Ligation of the shunt resulted in resolution of hypoxemia. The outcome suggests that hepatic venous return to the pulmonary circulation is important in maintaining normal pulmonary vascular caliber.(2) Hepatopulmonary syndrome in inferior vena cava obstruction responding to cavoplasty. De BK, Sen S, Biswas PK, Sanyal R, Majumdar D, Biswas J. Gastroenterology 2000;118:192-196. (Reprinted with permission.) AbstractReports show that hepatopulmonary syndrome mostly occurs in the setting of advanced hepatic dysfunction, with the associated vasoactive substance imbalance believed to be responsible for its pathogenesis. However, hepatopulmonary syndrome has also been reported in cases of mild hepatic dysfunction or noncirrhotic portal hypertension, indicating that portal hypertension also plays a part in the pathogenesis. Liver transplantation remains the only therapeutic option of proven benefit. We describe 2 cases of hepatopulmonary syndrome in the setting of inferior vena cava (suprahepatic) obstruction, but with minimal hepatic dysfunction. After balloon cavoplasty, 1 patient showed, in addition to improvement of the features of hepatic outflow obstruction, significant reduction of dyspnea, cyanosis, and hypoxemia with arterial blood gas normalization within 2 weeks and intrapulmonary shunt reversal within 8 weeks. This implies that hemodynamic alterations (such as portal hypertension) independently contribute to the pathogenesis of hepatopulmonary syndrome in at least some of the cases. Therapies aimed at correcting these abnormal hemodynamics may be important in the treatment of this condition, especially when the hepatic functional status by itself does not warrant a liver transplant.

Evidence for an Association Between Intrahepatic Vascular Changes and the Development of Hepatopulmonary Syndrome

“…This hypothesis is supported by the activation of the VEGF pathway in the lungs of rats with HPS 37 . The observation of more frequent HPS in patients with liver hypoxia induced by Budd Chiari syndrome (28%) or hypoxic hepatitis (46%) than in patients with extrahepatic portal vein thrombosis without cirrhosis (4%) is consistent with this view [38][39][40][41] .…”

Pediatric hepatopulmonary syndrome is seen with polysplenia/interrupted inferior vena cava and without cirrhosis

“…Krowka2 had previously noted that in noncirrhotic HPS cases, a degree of liver injury could not be excluded. We postulate that intrahepatic blood flow is altered in cases of noncirrhotic HPS, and that this can be identified through histologic changes that are characteristic of decreased and regionally variable portal venous inflow.…”

“…The pathophysiology of HPS is not understood. A hepatically mediated imbalance between the pulmonary vasodilators and vasoconstrictors has been hypothesized to promote the development of IPVD in HPS 2. Putative humoral mediators may include nitric oxide and endothelin‐1 3…”

Hepatopulmonary syndrome

“…HPS is relatively common, occurring in up to 30% of patients with cirrhosis [1,2]. The syndrome may occur in patients with comorbid primary lung diseases [4,5], and having cirrhosis is not imperative as HPS has been described in acute and chronic hepatitis without cirrhosis or portal hypertension [6,7] as well as in noncirrhotic portal hypertension without chronic liver disease [8][9][10][11]. The diagnostic criteria for HPS include documentation of impaired oxygenation and intrapulmonary vasodilatation (IPVD) in the setting of chronic liver disease or portal hypertension [3] (see list below).…”