To describe and review the imaging findings of transient hepatic attenuation difference (THAD) in patients submitted to dual-phase liver CT, in everyday clinical imaging.

THAD is defined as increased attenuation difference during the arterial phase, becoming isodense to parenchyma during the portal-venous phase. Morphologically THAD is classified into lobar multisegmental, sectorial, polymorphous, and diffuse. Many focal liver lesions, benign, malignant and inflammatory may accompany THAD. THAD may be the result of vascular abnormalities(arterioportral shunts, vascular compressions/variations), inflammatory changes and parenchymal compression.

We retrospectively evaluated 14 patients, submitted to dual-liver CT. Patients’ mean age was~ 62 (range 52-75years) and M:F ratio 2:1. Scanning was performed with 16x lightspeed MDCT, GE. NECT and dynamic CECT images (thickness 1.25mm) after IVCM100-120ml(infusion rate 3.5ml/sec), in arterial and portal-venous phase were acquired. Axial and MPR images were reviewed. Geographical areas of increased enhancement, during the arterial-phase (nearby the underlying pathology), becoming isodense in the portal-venous phase were depicted in all cases. Underlying causes were: cholangitis(5 patients), portal vein thrombosis±HCC(3 patients), cholecystitis(1...

THAD in dual-CT imaging of the liver is very frequent and it is a notorious culprit for the creation of liver pseudolesions. Radiologists must be familiar with this usual pitfall, in order to avoid misdiagnosis. When THAD is detected it is imperative to look carefully for the real underlying cause.

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