Gadoxetic acid-enhanced MRI of transient hepatic enhancement differences: Another cause of hypointense observation on hepatobiliary phase

Purpose: To retrospectively determine the frequency, natural history and factors associated with the presence of transient hepatic enhancement difference showing hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced MRI. Materials and methods: Gadoxetic acid-enhanced MRI of 125 patients (91 men; 34 women) with transient hepatic enhancement difference were retrospectively reviewed. Three readers qualitatively and quantitatively evaluated MR imaging features and evolution at follow up. The Chi-square test, Fisher's exact test and Kruskall-Wallis rank test were used for statistical analysis. Results: Transient hepatic enhancement difference were hypointense on hepatobiliary phase images in 20 of 125 cases (16%). At univariate analysis there was association with wedge-shape morphology (p < 0.001), size ≥21 mm (p < 0.001), hyperintensity on T2-weighted imaging (p < 0.001), restricted diffusion (p < 0.001) and previous treatment (p < 0.005). At multivariate analysis, the following factors were associated: previous treatment (p < 0.05), hyperintensity on T2-weighted imaging (p < 0.001) and size ≥21 mm (p < 0.001). Of 12 patients with hypointense transient hepatic enhancement difference on hepatobiliary phase images who had follow-up MRI, nine showed reduction in size. Conclusion: Transient hepatic enhancement difference observations showing hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced MRI are not infrequent and may shrink at follow-up. They are more likely associated with size ≥21 mm, hyperintensity on T2-weighted images and previous treatment of adjacent tumor.