Hepatic focal lesions: role of color Doppler ultrasonography with contrast media

Background: The differential diagnosis of focal hepatic lesions is still studied by diagnostic imaging operators. A big step forward in the field of ultrasound (US) has come from the color Doppler mode permitting accurate studies of the vascularization of focal hepatic lesions. Echocontrast agents have further improved color Doppler sensitivity to slow flows and have permitted to visualize intralesional vascular signals which were missed at B-mode US. New data have thus been acquired which can be integrated with flowmetric findings to help make the correct differential diagnosis with a fair safety margin. We studied the pathognomonic US pattern for each type of lesion.

Methods: We examined 55 patients with single hepatic lesions which had already been typified: they were 10 hepatic angiomas, 3 focal nodular hyperplasias (FNH), 2 hepatic adenomas, 20 hepatocarcinomas and 20 hepatic metastases. Color Doppler investigations were performed on each patient before and after the intravenous (i.v.) administration of an echocontrast agent (Levovist, Schering AG, Berlin, Germany). For each lesion we studied the morphological characteristics, the resistance index (RI) of intralesional arterial vessels, the hepatic perfusion index and the maximum speed in intralesional vessels.

Results: Contrast-enhanced US showed no intralesional signals or afferent branches in 8 hepatic angiomas, which however exhibited some peripheral vascularization; weak intralesional vascular signals were demonstrated in 2 cavernous angiomas. Intralesional signals, as well as peripheral vascularization, were detected in the 3 FNH cases, which also exhibited a centripetal afferent branch; the hepatic perfusion index in these lesions never exceeded .25. The two hepatic adenomas had similar color flowmetry to FNH also after i.v. contrast agent administration, except for the contripetal afferent vessel which was not seen. In the 20 hepatocarcinomas, contrast-enhanced images showed numerous intralesional signals and afferent branches which, with the peripheral vascularization, resulted in a basket-like pattern. Flowmetry of intralesional arterial vessels showed an irregular systodiastolic range, with RI = .32 +/- .5 in 12 lesions and high in the remaining 8 lesions (RI = .82 +/- 10). The hepatic perfusion index was .65 +/- 10 in all patients. In 14 of the 20 hepatic metastases, B-mode US showed no intralesional signals except for 6 metastases from colorectal carcinoma, and contrast-enhanced findings were about the same. The hepatic perfusion index at flowmetry ranged .30 to .45 in all patients.