Diagnostic Features of Real-Time Contrast-Enhanced Ultrasound in Focal Nodular Hyperplasia of the Liver

Purpose: The typical appearance of focal nodular hyperplasia (FNH) in radiological contrast techniques (helical CT or MRI) includes homogeneous enhancement in the arterial phase, but the exact timing for the best visualization of this pattern is unknown. The aim of the present study was to assess the ultrasound pattern of FNH with special attention to real- time contrast- enhanced ultrasonography (CEUS) appearance and specifically to the timing of perfusion patterns. Materials and Methods: 72 patients (60 females, 12 males) with a total of 90 FNH nodules with a diameter ranging from 8 to 100mm (mean +/- SD, 40.6 +/- 21.5mm) were examined continuously for at least 4 minutes using CnTI (R) and CPS (R) methods (ESAOTE (TM), Genoa, Italy and Acuson- Siemens T) after bolus injection of SonoVue (R) (BRACCO (TM), Milan, Italy). Results: 87 of 90 nodules showed the typical coinlike hyperechogenicity in the arterial phase. The remaining three nodules were all in the same patient and were diagnosed as FNH after resection. Contrast started to appear within the lesions after a mean of 15.7 +/- 4.6 seconds (range 7 - 27 s) and reached peak signal intensity, with the greatest differentiation between the lesion and the surrounding parenchyma, at around 22.6 +/- 7.0 seconds (range 14 - 72 s). In the late phase, 65 lesions (72.2%) became isoechoic (after a mean of 80.8 +/- 85.7 s, range 20 - 300 s), 22 (24.4%) slightly hyperechoic and 3 (3.3%) faintly hypoechoic. Conclusion: FNH shows a typical homogeneous hyperechoic pattern during the arterial phase in real- time CEUS which disappears slowly on average but occasionally even as soon as 20 seconds after contrast injection. If the first scans are taken later than 20 seconds after injection (which is still considered to be a full arterial phase), the ultrasound hyperechogenicity may be missed in some cases. Real-time study of these lesions is therefore strongly recommended to avoid possible false-negative results.