A Better Option for Diagnosing Ovarian Remnant Syndrome

Veterinarians want solid evidence of an ovarian remnant before performing exploratory surgery on a previously spayed bitch exhibiting signs of estrus. They also desire a reliable and non-invasive test to determine the spay status of a bitch with unknown medical history. There are limitations to each of the currently available diagnostic methods for ovarian remnant syndrome, but thanks to funding from AKC Canine Health Foundation (CHF) Grant 02188-A, a better testing option has been described.

Ovarian remnant syndrome occurs when signs of functional ovarian tissue occur in a previously spayed (via ovariohysterectomy (OHE) or ovariectomy (OE)) bitch.

Limitations of current testing methods:
1)      Vaginal cytology - the bitch must be in late proestrus or estrus to identify cornified epithelial cells on cytology.
2)      Sex hormone serology – serum levels of estrogen, progesterone, and luteinizing hormone vary throughout the estrus cycle.
3)      Responsive serology testing – measuring serum progesterone or luteinizing hormone after stimulation with an injection of gonadotropin releasing hormone (GnRH) is costly and requires two blood samples.
4)      Ultrasound – visualization of ovarian tissue with ultrasound depends on the size of the remnant, the stage of estrus at examination, and the skill of the examiner.
5)      Anti-Müllerian Hormone – a qualitative ELISA test is available to measure serum Anti-Müllerian Hormone (Spaychek®, manufactured by Preventia Diagnostics, Inc.), but not all canine ovarian tissue secretes this hormone.

Physiology
The gonads are the only source of Anti-Müllerian Hormone (AMH) in mammals. AMH is secreted by Sertoli cells in the fetal testes and prevents the Müllerian ducts from developing into the oviducts, uterus, and upper vagina in males. In females, granulosa cells in the ovaries begin to secrete AMH after duct development is complete. AMH secretion wanes as ovarian follicles mature and following ovulation, the corpus lutea does not secrete AMH but does secrete progesterone.

A better option
Knowing that serum AMH will be negative if an ovarian remnant contains only luteal tissue, CHF-funded researchers found that measuring the combination of serum AMH and progesterone is superior to measuring either hormone individually and recently published their findings in the Journal of the American Veterinary Medical Association.¹ They tested serum AMH and progesterone in 602 dogs being evaluated for ovarian remnant syndrome and invited submitting veterinarians to also submit any tissue excised during surgery for histopathology. Out of forty-eight dogs with ovarian remnant syndrome confirmed by histopathology, 52% were positive for both hormones, 35% were positive for at least one of the hormones, and the remainder had at least one inconclusive result. Of note is the fact that no dogs with an ovarian remnant were confirmed negative for both hormones.

Thanks to the AKC Canine Health Foundation and its donors, veterinarians now have a better tool to diagnose ovarian remnant syndrome and to determine the sex status of bitches with unknown medical history. Because the functional structures that produce AMH and progesterone differ and are affected by the stage of estrus cycle, measuring these hormones in combination is an effective test for ovarian remnant syndrome.

Learn more about CHF-funded research at akcchf.org/research.

References:
1. Place, N. J., Cheraskin, J.-L., & Hansen, B. S. (2019). Evaluation of combined assessments of serum anti-Müllerian hormone and progesterone concentrations for the diagnosis of ovarian remnant syndrome in dogs. Journal of the American Veterinary Medical Association, 254(9), 1067–1072.
https://doi.org/10.2460/javma.254.9.1067