Pseudotumoral presentation of nodular regenerative hyperplasia of the liver: imaging in five patients including MR imaging.

Nodular regenerative hyperplasia (NRH) of the liver is a condition characterized by multiple monoacinar regenerative nodules in the absence of fibrous septa. When these nodules become confluent they may be seen with sonography or CT. The appearance of these pseudotumoral pattern of NRH has been scarcely described with MRI. We present the imaging findings of five patients with NRH and a pseudotumoral form at sonography. Sonography depicted hyperechoic lesions in four patients and hypoechoic lesions in another. Computed tomography showed hypodense lesions with little contrast enhancement in two patients. Three patients showed subtle focal liver lesions on MRI: isointense in one, mildly hypointense in another, and minimally hyperintense in a patient with siderosis. The dynamic behavior at MRI was similar to the normal liver parenchyma. Hyperechoic lesions on sonography or hypodense lesions on CT, barely or not seen on MRI, can be indicative of NRH in an appropriate clinical setting.