Macro-regenerative nodules in biliary atresia: CT/MRI findings and their pathological relations

Aim: To describe the radiological findings of a macro-regenerative nodule (MRN) in the liver of pre-transplantation biliary atresia (BA) patients and to correlate it with histological findings. Methods: Between August 1990 and November 2007, 144 BA patients underwent liver transplantation (LT) at our institution. The pre-transplantation computer tomograghy (CT) and magnetic resonance imaging (MRI) findings were reviewed and correlated with the post-transplantation pathological findings. Results: Nine tumor lesions in 7 patients were diagnosed in explanted livers. The post-transplantation pathological findings showed that all the lesions were MRNs without malignant features. No small nodule was detected by either MRI or CT. Of the 8 detectable lesions, 6 (75%) were in the central part of the liver, 5 (63%) were larger than 5 cm, 5 (63%) had intratumor tubular structures, 3 (38%) showed enhancing fibrous septa, 3 (38%) had arterial enhancement in CT, one (13%) showed enhancement in MRI, and one (13%) had internal calcifications. Conclusion: Although varied in radiological appearance, MRN can be differentiated from hepatocellular carcinoma (HCC) in most of BA patients awaiting LT. The presence of an arterial-enhancing nodule does not imply that LT is withheld solely on the basis of presumed malignancy by imaging studies. Liver biopsy may be required in aid of diagnostic imaging to exclude malignancy.