Focal nodular hyperplasia in normal and fatty liver: a qualitative and quantitative evaluation with contrast-enhanced ultrasound

The aim of this study was to describe gray-scale appearance of liver parenchyma and focal nodular hyperplasia (FNH) by pulse inversion (PI) ultrasound (US) at baseline and after contrast agent administration in patients with normal and fatty liver. Sixteen consecutive patients (12 women, 4 men) with 29 previously diagnosed FNHs (15 of 29 located in normal liver and 14 of 29 in fatty liver) underwent PI US before and after SH U 508A (Levovist) injection. Signal intensity values were measured within the FNHs and the adjacent liver parenchyma in selected images. Baseline echogenicity of fatty liver was higher (15.19+/-2.90 dB+/-SD) than normal liver (10.91+/-3.15 dB+/-SD; p<0.001). After Levovist administration, normal livers (7 of 16) showed a statistically significant increase of echogenicity (16.59+/-3.81 dB+/-SD; p<0.001) in comparison with fatty livers (9 of 16; 15.75+/-3.12 dB+/-SD). The FNHs located in normal liver showed baseline echogenicity higher (12.29+/-3.22 dB+/-SD) than that of FNHs arising in fatty liver (7.06+/-2.43 dB+/-SD; p<0.001). After Levovist administration, FNHs located in normal liver showed a statistically significant increase of echogenicity (25.30+/-4.62 dB+/-SD) in comparison with FNHs located in fatty liver (13.58+/-3.54 dB+/-SD; p<0.001); the latter always showed mean values of echogenicity lower than surrounding liver parenchyma. In our series decreased contrast-enhancement pattern of both fatty liver and FNHs located in fatty liver was the most prominent finding when Levovist is administered. Contrast washout was a distinctive feature of FNH arising from the fatty liver.