CT and MRI diagnosis of hepatic focal nodular hyperplasia

Objective:To explore the characteristic findings of CT and MRI examinations in patients with focal nodular hyperplasia(FNH) of liver.Methods:All the CT and MRI findings of 19 cases with FNH confirmed by histopathology or clinicaldata were discussed retrospectively.16 patients examined with CT,10 cases with MRI scan,and 7 patients underwent both.All the imaging features were analyzed in combination with pathological findings.Results:All cases showed a solitary nodules or lobulated mass in the liver.The lesions were approximately 2 to 10 cm in diameter with an average diameter about 3.5cm.On plain CT scan,homogeneous area in 9 cases and slightly hypoattenuating zone were noted compared with the normal liver.The lesions showed heterogeneous or homogeneous hypodensity.On dynamic enhanced CT following intravenous contrast medium administration,all the lesions showed an early intensity and homogeneous enhancement except the central scars during arterial phase.7 cases displayed hyperattenuating and 9 cases demonstrated isoattenuation during the portal vein phase,5 cases showed hyperattenuating and 11 cases isoattenuattion during the equilibrium and delay phase.The central scars within 6 lesions showed delayed enhancement.On unenhanced MRI,10 cases showed hypointensity on T1WI and hyperintensity on T2WI.Dynamic contrast enhanced MRI with gadolinium DTPA showed enhancement pattern similar to that observed on contrast enhanced dynamic CT.All the lesions showed an early intensity and homogeneous enhancement during arterial phase,hyperintensity or hypointensity noted during the portal vein and equilibrium phase.Central scars within 4 lesions showed delayed enhancement.Conclusion:Typical cases with FNH show intense and homogeneous enhancement during arterial phase on dynamic enhanced CT and MRI following intravenous contrast medium administration.Hyperdensity or isodensity is displayed during portal vein phase and equilibrium phase.Crannied central scars with delayed enhancement are helpful to make differential diagnosis from hepatocellular carcinoma,hepatocelluar adenoma and hemangiomas.