PURPOSE: The purpose of this study was to evaluate the enhancement patterns and morphologic features ofhepatic abscesses, as seen on three-phase helical CT images. MATERIALS AND METHODS: Three-phase helical CT imagesof 22 clinically and pathologically proven hepatic abscesses more than 3 cm in diameter in 21 patients wereretrospectively reviewed. Three-phase helical CT scans were obtained at 30 sec(hepatic arterial phase, AP), 70sec(portal venous phase, PP) and 3 min(equilibrium phase, EP) after the start of intravenous infusion of contrastmaterial. We analyzed the number of abscess layers and their enhancement patterns during each phase, and evaluatedthe size and shape of abscess, the CT attenuation and presence of septae in the abscess cavity, and the thicknessand maturation of the granulation layer and collagenous wall. RESULTS: AP images showed that 13 abscesses(59%)had four layers; on PP images, half the abscesses were seen to have three layers, while EP images showed thattwo-thirds had two layers. Among the 13 abscesses with four layers seen on AP images, all abscess cavities andgranulation layers were hypo- and hyperattenuating, respectively, during all three phases. Most hypoattenuatingcollagenous walls seen on AP images became iso- or hyperattenuating on EP images, while hyperattenuatinghyperperfusion zones seen on AP images became isoattenuating during later phases. The degree of maturation of thecollagenous wall correlated with the number of abscess layers. CONCLUSION: As seen on AP, PP and EP three-phasehelical CT images, hepatic abscess frequently had four, three, or two layers respectively. More mature collagenouswalls tended to have more abscess layers.