Defining a species-specific K constant in American Bullfrogs (Lithobates catesbeianus) through use of computed tomography.

Objective: To use CT measurements to define the body surface area (BSA) formula in American bullfrogs (Lithobates catesbeianus) and calculate the species-specific shape constant (K) to suggest chemotherapeutic doses.
Animals: 12 American bullfrogs owned by the North Carolina State College of Veterinary Medicine Department of Laboratory Animal Resources underwent CT scans without anesthesia or sedation in November 2022.
Methods: As part of this prospective study, each American bullfrog underwent a complete physical exam and CT scan. 3-D surface models were created using CT data, and the resulting measurements were used for BSA calculations. Animals were grouped by sex. Nonlinear regression analysis of BSA versus body weight was performed, and a species-specific formula was derived for calculating BSA in American bullfrogs.
Results: The mean body weight of the bullfrogs was 354 grams. The mean CT-derived BSA was 414.92 cm2. The calculated K constant was 8.28 for the 12 American bullfrogs, and the CT-derived BSA formula was BSA in cm2 = 8.28 X (body weight in g)2/3. The K constant was 8.07 for females and 8.44 for males and was not significantly different between sexes (P = .5).
Clinical Relevance: Results indicated that the species-specific K constant for American bullfrogs is 8.28. This is the first calculated K constant that exists for amphibians to our knowledge.