Nine cases with marked retention of indocyanine green test and normal sulfobromophthalein test without abnormal liver histology: constitutional indocyanine green excretory defect.

Nine patients revealed marked retention in the indocyanine green (ICG) test and the normal sulfobromophthalein (BSP) test. The results of liver function tests in these cases were within normal limits with the exception of the ICG test. The ICG plasma disappearance rate ranged from 0.017 to 0.025, whereas that of BSP ranged from 0.058 to 0.126. The transfer rate of ICG from plasma to liver markedly decreased on two-compartmental analysis of the ICG decay curve. A transient delay of the ICG plasma disappearance (step formation) on the decay curve was observed over 20 to 25 minutes after an injection in all cases after repeated observation. Binding of ICG to plasma proteins in these cases failed to demonstrate a significant difference from normal subjects. The fasting serum bile acid levels in two cases and postprandial serum bile acid level in one case were normal. Light microscopic findings of the liver revealed normal histology. Electron microscopic findings showed increase of lipofuscin-like lysosomes, modification and paracrystalline-like array of mitochondria, and an increase of reticulum fiber in Disse's space. It is suggested that these cases represent a new type of dye excretory disorder of the liver with impaired hepatic uptake of ICG.