Utility of IV Iodinated Contrast for Diagnosis and Surgical Planning of Gonadal Neoplasms in Koi (Cyprinus carpio)
1Department of Veterinary Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA; 2Department of Veterinary Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA; 3California Animal Health and Food Safety Laboratory (CAHFS), San Bernardino Branch, University of California-Davis, Davis, CA, USA; 4Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
Computed tomography (CT) offers a rapid, repeatable, and comprehensive advanced imaging by minimizing anatomic superimposition and operator variability. In many species, CT is utilized for numerous purposes, such as lesion characterization and treatment planning. Intravenous (IV) iodinated contrast is commonly administered to improve vasculature conspicuity and further assess parenchymal organs. Typical distribution and pharmacokinetics of IV contrast have recently been investigated and established in healthy adult koi (Cyprinus carpio) via caudal vein injection.1,2 Clinical applications of IV contrast in diseased koi have since begun.
Gonadal neoplasms have been reported as the most common coelomic neoplasm in koi.3 The goal of this study was to apply the use of IV contrast in CT to a common koi disease state to evaluate its clinical utility relative to other imaging diagnostics. Four adult koi of various ages were diagnosed with coelomic masses on ultrasound examinations. In three cases, the coelomic masses were very large, hindering complete ultrasound evaluation of margins. In one case, the gonadal masses were smaller and surrounded by normal gonadal tissue on ultrasound. Further evaluation of coelomic masses was pursued with IV contrast-enhanced CT examinations. Intravenous contrast was successfully administered to all fish, and the margins of the masses could be delineated in all. CT imaging provided improved delineation compared to ultrasound in the three larger gonadal mass cases; however, it was inferior to ultrasound for the fourth fish with smaller masses surrounded by normal gonadal tissue. Surgical debulking or removal of the gonadal masses was performed in all four fish. All gonadal tissues were evaluated histologically. Recheck CT was performed in two fish approximately 5 months later, documenting residual neoplastic tissue or regrowth of sex cord stromal tumor in both fish. Nonetheless, the owner reported improved quality of life related to swimming ability and positioning in the water column.
This study documents successful application of IV contrast in koi with gonadal neoplasms, resulting in improved demarcation of margination of large tumors compared to ultrasound. Additional investigations of IV contrast-enhanced CT in different coelomic disease states and mass types in koi are needed to further explore its clinical utility.
*Presenting author
Literature Cited
1. Brust K, Phillips K, Kaufman M, et al. Intravenous contrast-enhanced computed tomography in adult koi (Cyprinus carpio). J Zoo Wildl Med. 2021;52.
2. Kaufman M, Knych H, Brust K, et al. Intravenous iopamidol pharmacokinetics in common carp (Cyprinus carpio). J Zoo Wildl Med. 2021;51.
3. Ott Knüsel F, Knüsel R, Doherr M, et al. Frequency and histologic characterization of coelomatic neoplasms in koi Cyprinus carpio koi. Dis Aquat Org. 2016;119:219–229.