Pitfalls in Differentiation between Solitary Hepatic IVletastasis and Hepatic Abscess on CT

ABSTRACT

OBJECTIVE: During the follow-up period of extrahepatic malignancy, one may encounter a solitary hepatic metastasis on CT scan which may be difficult to differentiate from hepatic abscess in an ambiguous clinical setting. It was our intention to copmare the radiological similarities and differences between two disease entities from which differentiation can be attempted. MATERIALS AND METHODS: Thirty-six cases of solitary heaptic meastesis and 23 cases of liver abscess were included in this study. Two radiologists interpreted the CT without knowledge of the clinical informations. CT pattern was categorized and the frequency of various findings were compared between the two groups. CT findings of the mass were analysed in misinterpreted cases. RESULTS: Without the clinical informations, the diagnostic accuracy of the mass was 72-76% without pattern analysis. Homogeneous masses were seen in both groups, but all masses larger than 4cm were metastases. In heterogeneous masses, metatases more frequently accompanied high attenuation in central or peripheral portion of the mass and showed thick intermediate zone, Irregular trabecular pattern or septations were more frequently observed in abscesses. Biliary dilatation or stone, pleural effusion, air in mass or biliary tree were more frequently seen in abscesses. The false diagnosis was encountered most frequently when the mass possessed any of the followings; homogeneous attenuation, mosaic pattern in the mass with inhomogeneous attenuation and thin intermediate attenuation area. CONCLUSION: Pattern analysis of the various CT character will be helpful to differentiate hepatic abscess and solitary hepatic metastasis in the equivocal clinical settings. However, similar pattern can be seen in both entities ;in this cases, corrdination of CT pattern and secondary findings is needed for better differentiation.