Purpose: Evaluate Gadoxetate Disodium enhanced dual-energy CT for visualization of perihilar cholangiocarcinoma by exploiting the hepatobiliary uptake of Gadoxetate Disodium and viewing images at the k-edge of gadolinium on the spectrum of simulated monoenergetic energies available with Dual Energy CT. Material and methods: In this prospective, IRB-approved study in patients with suspected cholangiocarcinoma, subjects who underwent a clinically indicated Gadoxetate Disodium liver MRI were immediately scanned without further IV contrast administration using rapid kVp-switching dual energy CT (rsDECT). Initial Gadoxetate Disodium dose was the FDA approved clinical dose, 0.025 mmol/kg; after additional IRB/FDA approval, 10 subjects were scanned with 0.05 mmol/kg. Both 50 keV and 70 keV simulated monoenergetic images as well as gadolinium(-water) material density images were viewed qualitatively and measured quantitatively for gadolinium uptake in the hepatic parenchyma and any focal lesions identified. Results: Of 18 subjects (mean age 55 years, 10M, 8F, weight 84 kg), eight were scanned with 0.025 mmol/kg (Group 1) and 10 with 0.05 mmol/kg Gadoxetate Disodium (Group 2). Five patients had cholangiocarcinoma (all in Group 1). On synthetic monoenergetic images using standard and double Gadoxetate Disodium dose, the liver parenchyma did not appear enhanced qualitatively. Comparison of mean hepatic parenchymal HU at 50 and 70 keV showed a measurable increase in attenuation at the lower viewing energy, which corresponded to the k-edge of gadolinium. No statistically significant difference was observed on quantitative gadolinium measurement of hepatic parenchyma for single versus double Gadoxetate Disodium dose using rsDECT gadolinium material density images. Of the five cholangiocarcinomas, the tumor to nontumoral hepatic tissue HU differences were 51.1 (32.2) (mean and std dev) and 49.0(26.5) at 50 and 70 keV, respectively. Conclusion: In this small pilot population, evaluation of potential hilar/perihilar cholangiocarcinoma using dual energy CT at both the single FDA-approved dose and double dose of gadolinium demonstrated observed differences in attenuation between the hepatic parenchyma and lesions. However, small sample size and heterogeneity of lesions warrants further investigation.