Contrast Enhanced Computed Tomography (CT) Of The Hepatobiliary Systems In Dogs And Cats: Protocols For Imaging Studies

Abstract

Introduction: Contrast enhanced computed tomography (CECT) of the abdomen in dogs and cats is a common diagnostic imaging study in clinical practice. CT is a rapid acquisition advanced imaging modality that provides cross sectional anatomy in high resolution. After the injection of an intravenous contrast agent, multiple phases of enhancement can be captured during CECT for vascular and parenchymal imaging.1,2,3,4 It is commonly indicated for detection of congenital portosystemic shunt in dogs and cats and for focal liver disease (e.g. primary or metastatic liver cancer).5 Abnormalities of the biliary system that may require advanced diagnostic imaging include biliary obstruction or rupture secondary to trauma or recent liver surgery.6,7

Aims: 1. Evaluate the influence of contrast injection technique on timing of enhancement of the liver in normal dogs and cats. 2. Develop a standardised protocol for multiphase CECT in dogs. 3. Identify the Ideal Dose of Iohexol in cats. 4. Develop a protocol for CECT of the biliary tract using a novel gadolinium-based contrast agent.

Method: Multiphase CECT will be performed in dogs and cats at the University Veterinary Teaching Hospital Sydney as a prospective clinical study. A multicentre collaborative study will be performed to compare different protocols for multiphase CECT in dogs. CT cholangiography will be performed experimentally in healthy research dogs.

Results and Conclusion: Patient body weight, contrast injection technique and contrast dose in dogs and cats are significant factors in multiphase CECT. A standardised protocol for multiphase CECT was developed using a regression formula to predict optimal timing of the arterial and liver parenchymal phase. A lowered dose rate for iohexol is recommended in cats based on our research. Biliary CT imaging using a gadolinium-based contrast agent was feasible in dogs but was cost prohibitive.