Use of human chorionic gonadotropin stimulation test to detect a retained testis in a cat.

A 4-year-old male cat was referred because of aggressive behavior and spraying urine. When the cat was 6 months old, only 1 testis was found in the scrotum. When the cat was 1 year old, the scrotal right testis was surgically removed and the left testis was not found, either within the scrotum or within the abdomen. The cat developed male behavior and another laparotomy was performed 1 year later, at which time the left testis could not be located. The cat continued to show male behavior. On referral, the penis was well developed and had spines. Human chorionic gonadotropin (HCG), 500 IU, was administered IV. At baseline, 30, and 120 minutes after HCG administration, serum testosterone activity (ng/ml) was 0.68, 5.0, and 10.5, respectively. Laparotomy was performed with the cat under general anesthesia. The left testis was found in the facial plane lateral to the symphysis pubis. Six weeks after the surgery, the HCG stimulation test was repeated and testosterone was not detected in any serum sample. The most practical solution to locate the undescended testis would have been to follow the intact ductus deferens to the testis adjacent to the pubic symphysis.