To elucidate the detectability of small hepatocellular carcinoma by various imaging modalities, we performed digital subtraction angiography, computed tomographic arterioportography and carbon dioxideenhanced ultrasonography. Of 76 patients with a small hepatocellular carcinoma of 2 cm or less in maximum diameter, 61 underwent digital subtraction angiog- raphy, computed tomographic arterioportography and enhanced ultrasonography at the same time. Concerning the 61 patients undergoing all the procedures, the characteristics of hepatocellular carcinoma were found in 57.4% (35 of 61) by digital subtraction angiography, 75.4% (46 of 61) by computed tomographic arterioportography and 72.1% (44 of 61) by enhanced ultrasonography. Among them, four hepatocellular carcinomas were detected only by enhanced ultrasonography, three were diagnosed only by computed tomographic arterioportography and two were diagnosed by both of them. Except for six hemangioma nodules that were easily diagnosed only with angiography, four of 55 benign hepatic nodules (7.3%) showed false-positive findings suggestive of hepatocellular carcinoma with either computed tomographic arterioportography or enhanced ultrasonography. In conclusion, computed tomographic arterioportography and enhanced ultrasonography could complementarily detect a small hepatocellular carcinoma more sensitively than digital subtraction angiography. (HEPATOLOGY 1994;20:82-87.) Hepatocellular carcinoma (HCC) is one of the most common neoplasms in Japan (1). Lately, as a result of the technological advances of ultrasonography (US) and computed tomography (CT), small HCCs have been often found during the follow-up period of liver cirrhosis (1-4). Although US is a more sensitive technique for detection of a small hepatic mass than CT or angiography, US images do not generally lead to the qualitative diagnosis of HCC.
Until recently, every HCC has been considered hypervascular (dense staining by contrast medium) through