Characteristics and management of constitutional indocyanine green excretory defect

Indocyanine green (ICG) test is a popular and widely implied assessment of hepatic functional reserve (HFR) due to its safety and efficiency. However, as the application of ICG expanded, an exceedingly rare disorder, the constitutional ICG excretory defect (CIED), gradually emerged. CIED is considered as a harmless dye excretory defect, which features remarkable ICG plasma retention (plasma ICG 15-min retention rate is higher than 50%) without any severe liver impairments. Previous investigations revealed that it has no particular symptoms and it is not a contraindication of surgical treatments. The deficiency of the organic anion transporting polypeptide 1B3 is affirmed to be the underlying cause of CIED. It is of great significance to identify this disorder from other reasons elevating ICG-R15 and provide such patients with effective and safe treatments. The utility of ^99mTc-GSA liver scintigraphy, Child-Pugh and ALBI scores, and liver biopsy in identification and supplementary HFR assessment in CIED has been affirmed. Moreover, other methods based on radioactive tracers, serum biomarkers and imaging examinations have potential. Based on existing evidence, we proposed a clinical strategy that prioritizes ALBI and Child-Pugh scores, as well as imaging examinations, such as computerized tomography and ultrasound examinations, for the initial identification of CIED. Thereafter, ^99mTc-GSA liver scintigraphy or biopsy is used to verify CIED and assess HFR. In conclusion, we comprehensively reviewed the characteristics, mechanisms and coping strategies of CIED, aiming to provide updated insights of this disorder.