INTRAVENOUS CONTRAST-ENHANCED COMPUTED TOMOGRAPHY IN ADULT KOI (CYPRINUS CARPIO)

IV iodinated contrast is undocumented in koi (Cyprinus carpio). IV contrast-enhanced computed tomography (CT) provides detailed imaging of the vascular structures and parenchymal organs. The goals of this study were to (1) document feasibility of IV contrast into the caudal vein, (2) determine distribution of contrast media and conspicuity of organs, (3) evaluate for differences in contrast uptake with two different doses of IV contrast, and (4) evaluate for contraindications of IV iodinated contrast in a small cohort of fish. Thirty adult koi were split into three groups (n = 10) in a prospective interrupted time series design with nonequivalent groups, receiving 480 mg iodine per kg (mg I/kg), 800 mg I/kg, and saline. Contrast doses were selected based on the range of doses used in other species. Half of the fish given IV contrast (n = 10) were imaged with CT. Physical exams, blood smears, and biochemistries were performed on all fish. Half of the fish in each group were euthanized 24 h after injection and the other half two weeks later. Necropsies and histopathology were performed to evaluate pathology associated with contrast. For the CT examinations, precontrast, immediate postcontrast, and 5-m delayed postcontrast CT scans were obtained. Contrast in coelomic organs and circulatory system was measured using Hounsfield units. The caudal kidney was the most contrast-enhancing organ. Both doses produced good vascular enhancement and similar distribution. The delayed postcontrast scans showed repeatable parenchymal enhancement of organs. No mortality was encountered. No abnormalities were detected on blood smears, necropsies, or histopathology. Results suggest IV contrast administration is feasible, both contrast doses provided valuable anatomical information in the study with CT of coelomic organs, and no contraindications of contrast administration were detected.