Transient hepatic attenuation differences
- CT finding: Transient hepatic attenuation differences (THAD)
- MRI finding: Transient hepatic intensity differneces (THID)
- Areas of parenchymal enhancement visible during the hepatic artery phase that are caused by the dual hepatic blood supply.
- Association with focal liver lesions.
- Four pathogenetic mechanisms:
- Directly by a siphoning effect (lobar multisegmental shape)
- Portal hypoperfusion (sectorial shape) due to portal branch compression or infiltration
- Thrombosis resulting in a portal branch blockade
- Flow diversion caused by an arterioportal shunt.
- Compensatory relationships between two liver sources of blood supply so that arterial flow increases when portal flow decreases as a result of communication among the main vessels, sinusoids, and peribiliary venules that open in response to autonomic nervous system and humoral factors activated by liver demand for oxygen and metabolites.
 Imaging Findings
 See Also
 External Links
Colagrande, Stefano, Centi, Nicoletta, Galdiero, Roberta, Ragozzino, Alfonso. Transient Hepatic Intensity Differences: Part 1, Those Associated with Focal Lesions. Am. J. Roentgenol. 2007 188: 154-159