Differentiation of small arterial enhancing hepatocellular carcinoma from non-tumorous arterioportal shunt with an emphasis on the precontrast CT scan

To evaluate the value of precontrast phase (PP) of quadriphasic CT for differentiation of small arterial enhancing hepatocellular carcinoma (HCC) from non-tumorous arterioportal (AP) shunt in patients with chronic liver disease. Forty-eight patients with 28 HCCs and 28 AP shunts were enrolled. All lesions (5-20 mm) showed arterial hyperenhancement with isoattenuation on portal venous phase or delayed phase without typical features of AP shunt. We evaluated and analyzed the attenuation of the lesions with qualitative and quantitative methods in each phase. The size, location, shape, margin, and coexistent HCC were evaluated. Diagnostic performances were also compared with triphasic CT and quadriphasic CT including PP in prediction of AP shunts from HCCs. The round or oval shape and visually low attenuation on PP were independent predictors for differentiating HCCs from AP shunts in multivariate analysis. Our study also revealed significantly increased diagnostic performances for both observers when PP was added to the triphasic CT. PP can be helpful in differentiation of small arterial enhancing HCCs from AP shunts. Careful evaluation of PP may lower need for follow-up CT or MRI, and can possibly achieve earlier diagnosis of small HCCs.