Imaging of focal nodular hyperplasia of the liver - Current status

Ranging behind hemangiomas, focal nodular hyperplasias (FNH) are the second most common benign solid liver lesions. Women between the age of 20 and 50 years are predominantly affected. In rare cases FNH may occur in children. Etiologically, an arteriovenous Vascular malformation of the liver is disc ussed, which causes pseudotumorous growth of the surrounding liver parenchy ma. Morphological features such as the presence of a radial vascular archit ecture and feeding arteries within a central scar are characteristic for th e presence of FNH. Imaging techniques which enable the depiction of the art erial blood supply with a characteristic centrifugal filling pattern, the c ontrast enhancement in the early arterial phase, the absence of calcificati ons and of a tumour capsule and the typical enhancement of the central scar , are of particular importance. Knowledge of these features is important in order to differentiate FNH from other hypervascular focal liver lesions wi th tendency of scar formation, such as hepatic adenomas, giant hemangiomas, hepatocellular and fibrolamellar carcinomas, and metastases. Diagnosis and differential diagnosis of FNH will be enabled by a combined modality appro ach consisting of (Doppler) sonography and triphasic CT. To confirm the dia gnosis of FNH, dynamic MRI is advisable. Because of the invasiveness of ang iography as well as the limited sensitivity and spatial resolution of the v arious scintigraphic methods, these modalities no longer play a role in the diagnostic workup of FNH. Lesions lacking typical features diagnostic for FNH remain subjects for biopsy and histological examination.