HIDA KINETICS IN CHILDREN

Quantitative analyses were performed on paediatric HIDA scans (EHIDA a nd DLSIDA) 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, impl ying '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 inf low rate into the liver was 0.003072 s(-1), which is similar to publis hed colloid uptake rates in normal livers. This implies that although the two radiopharmaceuticals are taken up by different mechanisms, bot h mechanisms have a very similar extraction fraction. Patients with ci rrhosis had a considerably reduced HIDA uptake rate (0.001072 s(-1)), and once again this was similar to colloid uptake from the blood in ci rrhosis. Patients investigated for neonatal jaundice all showed reduce d KTDA inflow, and this reduction was greatest (mean 0.000477 s(-1)) i n those neonates whose jaundice was due to hepatocellular impairment. In biliary atresia, the HIDA rate was reduced to approximately 0.00104 0 s(-1), which was still considerably higher than the rate from patien ts with neonatal jaundice due to sufficient hepatocellular impairment to cause complete cholestasis.