99mTechnetium-macroaggregated albumin perfusion lung scan versus contrast enhanced echocardiography in the diagnosis of the hepatopulmonary syndrome in children with chronic liver disease

Abstract

The hepatopulmonary syndrome (HPS) is a triad of advanced chronic liver disease (CLD), arterial hypoxemia and intrapulmonary arteriovenous shunting in the absence of a primary cardiopulmonary disease. HPS has been more frequently reported in adults than in children with no data on its prevalence in children with CLD. The aim of this study was to detect the prevalence of the HPS in a cohort of children with CLD because of chronic hepatitis B and/or C virus infection, schistosomiasis as well as inborn metabolic errors. We also aimed to evaluate the role of Technetium labeled macroaggregated albumin (Tc--MAA) perfusion lung scan versus contrast enhanced echocardiography (CEE) with intravenous injection of agitated saline in the diagnosis and quantification of intrapulmonary shunts and their relationship to important clinical and laboratory findings. Forty Egyptian children (22 males) were investigated. Their ages ranged from 5 to 12 years (with a mean of 9.5 years). Twenty individuals proved to have cirrhosis. Blood gas determination revealed more significant arterial hypoxemia in cirrhotics than noncirrhotics both under room air and after breathing 100% oxygen for 15 mins. CEE showed comparable cardiac measurements in cirrhotic and noncirrhotic patients, and diagnosed intrapulmonary shunts in three hypoxemic cirrhotic patients; whereas Tc--MAAperfusion lung scan diagnosed shunts in seven patients (five of them cirrhotic). The presence of shunts was significantly correlated with the duration of CLD, clinical findings, presence of cirrhosis and porto-systemic collaterals. We calculated for each patient a shunt index (SI) by the formula: (activity outside thorax/activity outside plus inside thorax) 100; and an SI value of 0.278 was found to be a cutoff value for shunt detection. All patients with SI above this value had shunting associated with hypoxemia and all patients with SI below this value had no hypoxemia (specificity 100%). Arterial hypoxemia and intrapulmonary shunts were diagnosed in 17.5% of this cohort of children with cirrhotic or noncirrhotic CLD representing the classic HPS. Tc--MAA perfusion lung scan was more sensitive than CEE in detection of intrapulmonary shunts. SI cutoff value of 0.278 was found to be highly specific for shunt detection and we recommend its validation in further studies.