Probability of hepatocellular carcinoma of small hepatocellular nodules undetectable by computed tomography during arterial portography

Recent advances in imaging modalities enable the identification of small he patocellular nodules. Among the imaging techniques currently used for detec ting hepatocellular carcinomas (HCC), computed tomography (CT) during arter ial portography (CTAP) is one of the most sensitive techniques available fo r detecting hemodynamic change. Even so, well-differentiated HCCs that disp lay only limited hemodynamic change, a feature shared with nonmalignant hep atocellular nodules, are not always detectable by CTAP. To improve our abil ity to distinguish well-differentiated HCCs from nonmalignant hepatocellula r nodules, we have attempted to clarify how the characteristics of the nodu les are shown by each imaging technique. We studied the imaging and patholo gical characteristics of 31 nodules (in 22 patients) detected by ultrasonog raphy (US), but not by CTAP. Histological diagnoses were as follows: HCC, 1 7 of 31 nodules (55%); high-grade dysplastic nodules, 1 of 31 (3%); and non malignant nodules, 13 of 31 (42%), Neither digital substraction angiography (DSA) nor CT arteriography (CTA) were able to detect any of the nodules. D etection rates for plain CT were: 5 of 17 (29%) HCC, 1 of 1 (100%) high-gra de dysplastic nodules, and 1 of 13 (8%) nonmalignant nodules. Detection rat es for T1/T2-weighted magnetic resonance imaging (MRI) were: 4 of 17 (24%) HCC, 1 of 1 (100%) high-grade dysplastic nodules, and 3 of 13 (23%) nonmali gnant nodules. Dynamic CT and dynamic MRI provided no additional informatio n. In conclusion, there is some probability that hepatocellular nodules det ected by US, but not by CTAP, are HCC, presently it is difficult to disting uish between benign nodules and malignant ones with these imaging technique s, and our findings indicate that biopsy may be advisable for nodules detec ted under these conditions.