Unilateral ductus deferens aplasia with terminal cystic dilation in a Bernese mountain dog

Abstract An incidental caudal abdominal mass was discovered in a 5‐year‐old, male, entire Bernese mountain dog. Investigations showed a terminal cystic dilation of the left ductus deferens. Castration, along with surgical resection of the mass, was performed, and histopathology of the mass and ductus deferens was consistent with segmental aplasia of the ductus deferens and a cystic remnant of the mesonephric duct. The patient returned to normal activity following surgery, but was euthanased 6 months after surgery due to an unrelated histiocytic sarcoma.