[Computerized tomography, magnetic resonance, and nuclear medicine in the non-invasive diagnosis of focal nodular hyperplasia of the liver].

INTRODUCTION: Focal nodular hyperplasia (FNH) is a benign liver lesion requiring a prompt diagnosis and a conservative management. Aim of our study was to prospectively integrate enhanced CT, MRI, nuclear medicine in the noninvasive diagnosis of FNH. MATERIAL AND METHODS: 20 FNH lesions (diameter ranging 1.5-13 cm) in 18 asymptomatic patients were investigated with MRI and nuclear medicine. MRI examinations were performed with a 1.5 T superconducting system (Philiphs NT) by acquiring T1-weighted, T2-weighted, T2-weighted fat-suppressed Turbo Spin-Echo and dynamic MRI sequences, with breath-hold T1-weighted Turbo Field Echo and Gd-DTPA. Nuclear medicine included in all cases 99mTc sulfur colloid or 99mTc iminodiacetic acid studies. Diagnostic sensitivity of MRI was compared with that of nuclear medicine, and the sensitivity of the two modalities combined. The definitive diagnosis was made by percutaneous core-needle biopsy (12 lesions), surgery (2 lesions) and longterm follow-up (6 lesions). RESULTS: In 13 lesions larger than 3.5 cm typical findings, such as the central scar and homogeneous pattern, were observed in 9 cases (75%) with enhanced CT, in 10 cases (83%) with unenhanced MRI and in 11 cases (91%) after gadolinium injection. Hepatobiliary scintigraphy showed increased tracer uptake in delayed scans in 10/12 cases (83%) while sulfur colloid studies were diagnostic in 2/12 cases only (16%), showing the same tracer uptake than the surrounding liver parenchyma. In 7 lesions smaller than 3.5 cm, only 1 case showed typical findings; dynamic MRI showed typical early hypervascularity in 5 of the 6 remaining lesions (71%) which persisted on late images. In lesions smaller than 3.5 cm, sulfur colloid studies were diagnostic in 1/7 lesions (14%) and hepatobiliary scintigraphy in 3/7 lesions (42%). Considering all 20 lesions, MRI-nuclear medicine integration performed better than MRI alone. CONCLUSIONS: Enhanced MRI and biliary scintigraphy are important tools to make the final diagnosis of FNH. In small lesions both examinations should performed, but in large lesions MRI may be sufficient to make an unquestionable diagnosis, limiting hepatobiliary scintigraphy to questionable cases.