Contrast ultrasound zeroes in on focal liver lesions

Sonographic examination with microbubble contrast agents can reliably characterize focal liver lesions, confirm or exclude hepatocellular carcinomas, and remove the need for more invasive, costly imaging, according to studies presented Monday.

Canadian researchers used contrast-enhanced ultrasound to evaluate 80 patients who presented during a nine-month period with 106 hepatic nodules that had a high likelihood of becoming malignant. The researchers characterized lesions during dynamic and portal vein phase scanning based on the lesions' enhancement patterns. They found that contrast sonography could characterize lesions early and obviate further scanning with CT or MR.

Contrast ultrasound confirmed 46 lesions as HCC, 31 as dysplastic/regenerative nodules, 16 as hemangiomas, eight as pseudomasses, and five as indeterminate nodules. Twenty-one out of 37 nodules detected at initial scanning were benign and were subjected to close surveillance with ultrasound only. None of these lesions evolved into HCC after the nine-month follow-up. Fifteen nodules were diagnosed as HCCs and one as a pseudomass.

Of 69 lesions with an indeterminate diagnosis at initial CT/MR scanning, contrast ultrasound identified 30 HCCs, 19 dysplastic/regenerative nodules, seven hemangiomas, and eight pseudomasses.

In a similar study, Italian researchers enrolled 191 consecutive patients with chronic diffuse liver disease due to chronic hepatitis B or C and cirrhosis. Using microbubble contrast sonography, the researchers accurately differentiated HCCs from other focal liver lesions.

As in the previous study, the investigators used the lesions' enhancement patterns at different phases to calculate positive predictive values. Two independent observers reviewed the studies. HCCs showed 40 diffuse homogeneous, 56 heterogeneous, 10 dotted, and five absent enhancement patterns at arterial phase. HCC also appeared as 71 hypoechoic lesions and 40 isoechoic lesions at late phase.

The investigators obtained the highest positive predictive value for HCCs by combining diffuse heterogeneous enhancement at arterial phase with hypoechoic appearance at late phase, with a PPV of 94% and overall accuracy in HCC characterization of 92%.