Intra-abdominal vas deferens cyst in a laboratory rhesus macaque (Macaca mulatta).

A 21-year-old male rhesus macaque presented with abdominal enlargement. The clinical, magnetic resonance imaging, and computerized tomography findings confirmed a large mass occupying the entire abdomen. The mass was surgically removed, and histopathology confirmed a vas deferens cyst. The macaque recovered uneventfully. The veterinarians should be aware of the possibility of an intra-abdominal vas deferens cyst and that, as our case shows, could be treated with surgical removal.