Because fights between territorial male lizards are violent and often fatal, reptile breeders frequently request sex determination before adding a new lizard to their group, especially for species that do not show evidence of sexual dimorphism.
This study aimed to evaluate diagnostic sensitivities of ultrasound, contrast radiography, and plain and contrast computed tomography (CT) for sex determination by identifying hemipenes in 4 popular lizard species: bearded dragons (Pogona vitticeps), Egyptian spiny-tailed lizards (Uromastyx aegyptia), blue-tongued skinks (Tiliqua scincoides), and Sudan plated lizards (Gerrhosaurus major).
Lizards of known sex (n = 19; 10 female, 9 male) were each subjected to all 4 imaging modalities, with blinded evaluators. In a few subjects, thick tail scales prevented ultrasound. Otherwise, all imaging was easily accomplished on nonsedated patients within 5 to 10 minutes; contrast agents were gently instilled through the cloaca. Contrast radiography and contrast CT were highly sensitive for detection of hemipenes (8/9 = 88.9% and 9/9 = 100%, respectively). With ultrasound and noncontrast CT, hemipenes were often difficult to distinguish from surrounding tissues. Although these results cannot be assumed to apply to other lizard species or juveniles, the methods and results from this study can serve as a reference for future research.