HIDA kinetics in children

Quantitative analyses were performed on paediatric HIDA scans (EHIDA and DISIDA) to measure the flow rates of HIDA into and out of the liver. Analysis of the tracer outflow rate indicated that HIDA appeared to leave the liver even when there was complete biliary obstruction, implying 'leakage' from hepatocytes back into the blood. This potentially explains why a 'hepatogram' does not provide useful information about hepatic obstruction, whereas a renogram does yield useful information about renal outflow obstruction. In a small group of patients with no evidence of either hepatocellular disease or obstruction, the HIDA inflow rate into the liver was 0.003072 s(-1), which is similar to published colloid uptake rates in normal livers. This implies that although the two radiopharmaceuticals are taken up by different mechanisms, both mechanisms have a very similar extraction fraction. Patients with cirrhosis had a considerably reduced HIDA uptake rate (0.001072 s[-1]), and once again this was similar to colloid uptake from the blood in cirrhosis. Patients investigated for neonatal jaundice all showed reduced HIDA inflow, and this reduction was greatest (mean 0.000477 s[-1]) in those neonates whose jaundice was due to hepatocellular impairment. In biliary atresia, the HIDA rate was reduced to approximately 0.001040 s(-1), which was still considerably higher than the rate from patients with neonatal jaundice due to sufficient hepatocellular impairment to cause complete cholestasis.