Definition:

• Intensity in the hepatobiliary phase that is identical or nearly identical to that of liver.

Usage:

• An observation that is visible on non-hepatobiliary phase sequence(s) but not observed on the hepatobiliary phase
• Ancillary feature that favors benignity.

If unsure whether an observation in the hepatobiliary phase is hypointense vs. isointense:     

• Characterize as hepatobiliary phase isointense                               

Synonyms:

• Synonyms: hepatobiliary phase isoenhancement
• Preferred terms: hepatobiliary phase isointensity
• Rationale for preferred terms:  Feature is descriptive of intensity relative to background liver parenchyma and may not truly represent the ability of the lesion to uptake or retain hepatobiliary contrast agents.

Background:

• Hepatobiliary phase iso-intensity is an ancillary feature that favors benignity and may be used to downgrade an observation by one or more categories.
• A hepatobiliary phase hypointense rim surrounding an iso- or hyperintense observation, thought to represent a tumor capsule, can be seen with HCC and is an ancillary feature that favors malignancy.  This feature may be used to upgrade an observation (up to but not beyond LR-4). 
• Currently, OPTN does not provide guidance regarding hepatobiliary phase imaging.