CT and MRI features of FNH
What is FNH, and what are its CT and MR imaging features?
FNH is the most commonly encountered benign hepatic lesion of hepatocellular origin, and is more frequently seen in women. FNH, usually identified as an incidental lesion on CT and MRI, is a focal regenerative response of hepatocytes to an underlying hepatic vascular malformation, which also contains Kupffer cells.
On MRI, FNH is typically isointense on T1-weighted images and T2-weighted images relative to liver parenchyma. On dynamic contrast-enhanced images, FNH shows intense homogeneous arterial phase enhancement, which becomes isointense to liver parenchyma on venous and delayed phase images. A central scar is often present, which has low T1-weighted and high T2-weighted signal intensity relative to liver parenchyma and does not enhance on arterial phase images, although delayed phase enhancement is typically seen. On hepatobiliary phase T1-weighted images, FNH retains hepatobiliary contrast material such that portions of the lesion will appear isointense or hyperintense to liver parenchyma.
FNH is usually not identifiable on unenhanced CT images, and it has no associated calcifications. The enhancement pattern of FNH on CT is similar to that on MRI.