Canine and feline ovarian remnant syndrome (ORS) is a condition in which a portion of ovarian tissue remains in the body after an ovariohysterectomy (spaying). This remnant tissue can continue to produce hormones, leading to symptoms of estrus (heat) in animals that should otherwise no longer be cycling.

 

Causes:

ORS in dogs and cats usually occurs due to:

* Incomplete removal of the ovaries during spaying surgery.
* Fragmentation of the ovarian tissue during the surgical procedure.
* Sometimes, there can be ectopic ovarian tissue, where small pieces of the ovary exist outside their normal location, which can be inadvertently left behind.

 

Symptoms:

The most common sign of ovarian remnant syndrome in both dogs and cats is the recurrence of heat cycles even after they’ve been spayed. Other symptoms may include:

* Swelling of the vulva.
* Vaginal discharge.
* Behavioral changes associated with being in heat, such as restlessness, increased affection, or aggression.
* Attraction of male animals due to pheromones released during heat.
* Mammary gland enlargement.

 

Diagnosis:

Diagnosis typically involves:

* Vaginal cytology: Examining cells from the vaginal wall under a microscope can show if the animal is in estrus.
* Hormonal assays: Measuring Anti-Müllerian hormone (AMH) and Progesterone. Since AMH is produced by ovarian tissue, detecting this hormone can confirm the presence of functional ovarian remnants. It is possible for a true ORS case to have a negative AMH test but a positive progesterone test since Pg is expressed in luteal tissue.
* Ultrasound: May help detect residual ovarian tissue.

 

Treatment:

The primary treatment for ORS in dogs and cats is surgical removal of the remaining ovarian tissue. This can be more complicated than a standard spay surgery because the tissue may be small or embedded in scar tissue.

 

Complications:

If not treated, ORS can lead to complications like:

* Recurrent heat cycles, which can cause frustration for owners.
* Increased risk of pyometra, a life-threatening infection of the uterus stump left after the initial spay.
* Hormonal-related cancers, though these are rare.

Proper surgical technique during the initial spay is key to preventing ORS, but even in the hands of experienced surgeons, it can occasionally occur.

 

About the Ansh Labs’ Canine Feline AMH ELSIA (AL-116) immunoassay:

Our kit uses specific and well-characterized antibodies with canine/feline AMH antigen as calibrators. The kit is also specifically optimized to minimize the false-positive results that may be generated due to canine anti-mouse antibodies present in serum. This generates accurate results as compared to other commercial kits that are modified human AMH kits.

 

The microplate has breakable wells on strips which allow for multiple runs until the number of samples is sufficient for a full plate. Both feline and canine samples can be run on a single plate. One kit can run 86 samples in singlets.

 

The kit comes with 2 lyophilized controls and 4 lyophilized calibrators, which are stable for up to 4 freeze thaws.

 

Other features:

* Sample Size: 25 µL
* Sensitivity: 0.015ng/mL
* Incubations: 2.5 hours
* Shelf Life: 24 months from date of manufacture

 

Reference Ranges:

Ansh Labs’ Canine AMH Reference Ranges:

 

Ansh Labs’ Feline AMH Reference Ranges:

 

Relevant Resources:

Feline reproductive function tests. Anti-Müllerian Hormone (AMH) Test for Ovarian Remnant Syndrome, Cryptorchidism and Determination of Spayed/Castrated vs. Intact. Cornell University College of Veterinary Medicine. (2022, July 18). Retrieved March 14, 2023, from https://www.vet.cornell.edu/animal-health-diagnostic-center/testing/protocols/feline-reproductive

 

Anti-Mullerian Hormone Testing: Feline and Canine. UC Davis Veterinary Medicine. (2023, Jan 24). Retrieved March 14, 2023, from https://www.vetmed.ucdavis.edu/labs/endo-lab/anti-mullerian-hormone-testing

 

Relevant Citations:

Hollinshead FK, Walker C, Hanlon DW. Determination of the normal reference interval for anti-Müllerian hormone (AMH) in bitches and use of AMH as a potential predictor of litter size. Reprod Domest Anim. 2017 Apr;52 Suppl 2:35-40.

 

Themmen APN, Kalra B, Visser JA, Kumar A, Savjani G, Gier J, Jaques S. The use of anti-Müllerian hormone as diagnostic for gonadectomy status in dogs. Theriogenology 86 (2016) 1467–1474.

 

Yilmaz O, Toydemir T, Kirsan I, Ucmak Z, Karacam E. Anti-Mullerian hormone as a diagnostic tool for ovarian remnant syndrome in bitches. Vet Res Commun. First published online June 24, 2015. (Full-Text available upon request)