Having your cat spayed is the solution to avoiding the signs of heat, but imagine you had your cat spayed and she continues to show signs of heat. That scenario is not fun for anyone, including the cat.
When cats are in heat (estrus) they act a bit, well, kooky (see sidebar). Often, there’s not much peace or restful nights in the household. Additionally, cats go into heat every two to three weeks for one to two weeks at a time, for most of the year. This boils down to breaks from this frantic feline behavior becoming few and far between.
But She Was Spayed
“Persistent heat cycles in a spayed pet can be a frustrating and worrying concern for pet owners and veterinarians,” says Dr. Jan MacDonald, Cornell University graduate and board-certified veterinary surgeon, who practices in Syracuse, N.Y. “When confronted with recurrent signs of heat, even years after a pet was spayed, a veterinarian needs to investigate for the reason why.”
The most common cause for this problem, called “feline ovarian remnant syndrome,” is that the surgeon inadvertently left part of an ovary behind during spay. The diagnosis of retained ovarian tissue can be made through blood tests, ultrasound, or exploration of the cat’s abdomen.
“It’s important that abdominal exploratory surgery be scheduled when the cat is actively showing signs of estrus, as this may make finding ovarian tissue easier,” says Dr. MacDonald.
Ectopic Tissue
“There have been cases of cats with microscopic ectopic (meaning in the wrong place) ovarian tissue in the ovarian pedicles, which became enlarged and functional once the normal ovaries were removed,” says Dr. MacDonald. “There is also a rare anatomical anomaly in cats and dogs, with failure of a kidney and uterine horn on one side to develop. These patients almost always have an ovary present on that side, but it may be located farther forward than expected,” potentially making this ovary more difficult for the surgeon to find and remove.
Ectopic ovarian tissue can occur in other random places in the abdomen, again making it difficult to find. A 2020 study published in the Journal of American Veterinary Medical Association described a case in which a cat required three abdominal exploratory surgeries before her condition was resolved.
Bloodwork First
The anti-müllerian hormone (AMH) test, which tests for AMH produced by ovarian tissue, is the most reliable blood test for diagnosing ovarian remnant syndrome. Your veterinarian will likely recommend this test first, as opposed to immediately recommending exploratory surgery. If the blood test is positive, ovarian tissue is in there somewhere, warranting the abdominal exploratory. If the test is negative, it is unlikely any ovarian tissue was left in the body.
Occasionally, there will be a false negative or inconclusive AMH test result. When this happens in spayed cats that are showing signs of heat cycles suggesting that active ovarian tissue is likely present, running a progesterone (P4) test in conjunction with the AMH may confirm the diagnosis, warranting abdominal exploratory.
Abdominal ultrasound may be recommended as part of the pre-surgical workup. Sometimes the ovarian remnant can be identified this way, especially when it was part of normal anatomy inadvertently left behind during the original spay procedure. This is useful information for the surgeon looking for the remnant. It is not uncommon, however, to have a negative or inconclusive ultrasound, as this tissue can be difficult to identify, and highly dependent on the experience and skills of the ultrasonographer.
The Surgery
Exploratory laparotomy—opening the abdomen and examining its contents—is the next step in the process of identifying and correcting feline ovarian remnant syndrome.
“The initial midline incision should be made to expose both kidneys,” says Dr. MacDonald, as the ovaries sit anatomically very close to the kidneys. “Careful palpation of each ovarian pedicle is done to check for ovarian tissue. The ureters (tubes going from the kidneys to the bladder) must be identified and protected during any tissue removal. If no ovarian tissue is found in either pedicle, the incision is enlarged to allow for full exploration of the abdomen.”
A biopsy on all removed tissue is needed to confirm ovarian remnant removal. “Successful removal of all retained ovarian tissue will resolve the persistent estrus signs,” says Dr. MacDonald.
Bottom Line
The takeaway from all this is that if your spayed female cat is showing signs of heat, you are probably not crazy. Contact your veterinarian. At the end of the day, your flirty feline friend will feel better and your home can return to a peaceful place for all.
