Monorchidism with ipsilateral renal agenesis in a cat

A 1-year-old intact male ragdoll weighing 5.9 kg was presented for general wellness examination and castration. Upon physical examination, neither testes could be palpated in the scrotum. Blood test results (complete blood cell count, serum biochemistry and electrolyte analysis) showed no remarkable findings. Radiographic and ultrasound examination did not detect the right kidney and testis in the abdominal cavity. However, we were unable to visualize the right kidney and testis in the abdominal cavity. An exploratory laparotomy for cryptorchidism revealed that although the left testis was intact, there was no right kidney, ureter and ipsilateral testis in the abdominal cavity. There were no remarkable findings upon histopathology of the left testis. Moreover, despite the presence of a unilateral kidney, blood analysis results were normal and the kidney was not enlarged due to compensatory hypertrophy. In females, there have been several case reports of urogenital agenesis or aplasia with compensatory hypertrophy of the contralateral kidney. This is the first case report of ipsilateral urogenital agenesis in a male cat without renal enlargement.