Ovarian remnant syndrome in a 2-year-old cat with inconclusive diagnostics.

Case summary: A 2.5-year-old, spayed female domestic shorthair cat was evaluated for estrus-like behavior (lordosis, vocalization and rolling) occurring on a cyclical basis every 3 weeks. Clinical signs began 6 months after ovariohysterectomy and exploratory abdominal surgery was performed; no ovarian tissue was found. On evaluation at a referral hospital, serum anti-Müllerian hormone (AMH) concentration was 0.14 ng/ml, consistent with a spayed female, and serum progesterone concentration was 1.3 ng/ml, which is not consistent with the presence of active luteal tissue. The cat returned while exhibiting estrus behavior and 90% of the vaginal epithelial cells seen on vaginal cytology were superficial. Serum AMH concentration at that time was again within the interval consistent with a spayed female (0.10 ng/ml). Gonadorelin was administered to induce ovulation; 3 weeks later, serum progesterone concentration was measured at 1.6 ng/ml, not consistent with the presence of active luteal tissue. Exploratory abdominal surgery was performed and a small 2 mm piece of ovarian tissue was removed from near the location of the right ovarian pedicle. No estrus-like behavior was observed in the weeks after the surgery. Relevance and novel information: This case study demonstrates that a very small amount of ovarian tissue can produce enough estradiol to stimulate estrus behavior in the cat and induce cornification of the vaginal epithelium, yet produce too little AMH to confirm its presence. Similarly, despite the formation and presence of luteal tissue, there was apparently too little progesterone secretion to confirm what is generally seen in an intact queen.