Abstract

Background:
Recently, the usefulness of triple-phase contrast-enhanced computed tomography (CT) scans for liver tumors in canines has been reported. However, detailed information on the CT findings of cholangiocarcinoma (CCA) and combined hepatocellular-cholangiocarcinoma (cHCC-CCA) remains limited.

Aim:
This study aimed to retrospectively evaluate triple-phase contrast-enhanced CT findings in canine CCA and cHCC-CCA using objective parameters, such as CT values and morphological characteristics.

Methods:
This study included eight dogs that underwent triple-phase contrast-enhanced CT scans and surgical removal and were pathologically diagnosed. Three CCA cases and five cHCC-CCA cases were analyzed. Parameters included CT values and mass sizes, CT values and lymph node sizes, and rim enhancement. “Rim enhancement” was defined as the contrast enhancement effect at the liver parenchyma–mass boundary.

Results:
CT values for CCA were as follows: pre-contrast: 43.9 ± 3.6 Hounsfield units (HU); arterial phase: 76.9 ± 22.5 HU; portal phase: 98.8 ± 37.7 HU; equilibrium phase: 90.9 ± 27.1 HU. For cHCC-CCA, the mean CT values were as follows: pre-contrast: 50.7 ± 6.1 HU; arterial phase: 80.2 ± 19.2 HU; portal phase: 95.0 ± 21.3 HU; equilibrium phase: 86.1 ± 13.4 HU. The peak contrast enhancement for both CCA and cHCC-CCA was in the portal phase. Rim enhancement appeared in the arterial phase in all CCA cases, whereas it appeared in the portal phase in 80% of cHCC-CCA cases, indicating a significant difference.

Conclusion:
Rim enhancement may help distinguish between CCA and cHCC-CCA. However, this study has a limited number of cases, and future large-scale, multicenter studies are warranted.

Key words: Canine; Cholangiocarcinoma; Combined hepatocellular-cholangiocarcinoma; Computed tomography; Dog.