Atypical enhancement pattern of hepatocellular carcinoma with portal vein thrombosis on multiphasic CT

ABSTRACT

<p><b>INTRODUCTION</b>The 2005 American Association for Study of Liver Diseases (AASLD) diagnostic criteria allow non-invasive diagnosis of hepatocellular carcinoma (HCC) based on their enhancement pattern but we have observed a high incidence of atypical enhancement characteristics in HCC associated with portal vein thrombosis. This study seeks to examine the radiological features of this particular subgroup.</p><p><b>MATERIALS AND METHODS</b>Patients with HCC and portal vein thrombosis who underwent pre-treatment multiphasic CT imaging were drawn from a surgical database. The arterial, portal venous and delayed phase images were assessed qualitatively and quantitatively (with region of interest [ROI] analysis) for lesion hypervascularity and washout. The background enhancement of the left and right lobes of the liver was also quantifi ed by ROI analysis.</p><p><b>RESULTS</b>Twenty-fi ve lesions in 25 patients were selected for analysis. Qualitative analysis showed that 10/25 (40%) lesions demonstrated arterial hypervascularity while 16/25 (64%) lesions showed washout. Ten out of 25 (40%) lesions demonstrated both arterial hypervascularity and washout. Quantitative analysis showed that the average absolute lesion enhancement from precontrast to arterial phases was 49.1 (± 17.1) HU for hypervascular lesions compared to 23.8 (± 16.6) HU for non-hypervascular lesions (P <0.01). The mean absolute enhancement of the background liver parenchyma in the arterial phase was 13.79 (± 7.9) HU for hypervascular lesions compared to 36.6 (± 30.6) HU for non-hypervascular lesions (P = 0.03).</p><p><b>CONCLUSION</b>A large proportion of HCC with portal vein thrombosis lack characteristic arterial hypervascularity, which may be secondary to compensatory increased arterial supply to the background liver. This is a potential pitfall when applying imaging criteria for diagnosis of HCC.</p>