Can A Spayed Dog Go Into Heat?

Can A Spayed Dog Go Into Heat?

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When a bitch is spayed, her ovaries and womb are completely removed from her body. It is not a reversible procedure. 

The removal of the womb and ovaries also stops the production of estrogen which is the hormone that triggers the dog’s heat cycle. 

Logically, a dog who has been spayed shouldn’t be able to go into heat. However, in some cases they do. 

Let’s take a closer look. 

The Estrus Cycle

Dog’s don’t technically menstruate. It is different from the cycle human women go through in a number of ways. 

Firstly, the bloody discharge that is secreted by a bitch in heat doesn’t come from the womb.

In humans, menstrual blood is the shed lining of the womb. However, in dogs, it is actually a vaginal discharge that’s a result of the increased blood flow to the area. 

Secondly, dogs don’t have monthly heat. Their estrus cycle takes about six months which means they only go into heat about twice a year. Smaller dogs may have 3 or possibly 4 cycles a year. Giant breeds may only have one. 

Finally, with dogs, the bloody discharge signals fertility. In humans, menstrual blood is the end of the cycle when they are less fertile.

The first sign of a bitch coming into heat is a swollen vulva. However, this isn’t always easy to spot. For many people, the first thing they notice is the bloody discharge on the floor or dog bed. 

This typically lasts for 10-14 days and the discharge becomes lighter in color and more watery as the cycle progresses. 

Spayed and in Heat

Dogs who have been spayed should no longer come into heat. They don’t have a uterus or ovaries to trigger the cycle. 

However, there are some reasons why your dog might appear to be in heat. 

Ovarian Remnant Syndrome

This condition affects dogs who have been spayed and it is fairly self explanatory. 

This condition occurs when functioning ovarian tissue is left in the dog. This tissue is still able to trigger hormone changes that start the heat cycle.

It doesn’t matter that the dog no longer has a womb because, if you remember, the bloody discharge comes from the vagina, not the womb. 

The main symptom of ovarian remnant syndrome is that your dog will still go into heat. If your fixed dog starts displaying heat behavior you should take them to the vet for a diagnosis. 

The vet will perform some of the following tests to check whether it is ovarian remnant syndrome. 

  • Vaginal Cytology – The vet will swab your dog’s vagina while they appear to be in heat. This swab will be put under a microscope to check for the presence of cornified cells. Cornified cells indicate that estrogen is present in the dog’s system. This test can’t outright diagnose ovarian remnant syndrome but it is used as a form of preliminary screening.
  • Baseline Hormone Levels – This test allows your vet to check whether your dog’s hormones are at a normal level. Increased estrogen can indicate ovarian remnant syndrome but it is not conclusive. This test is used less frequently because it is an unreliable indicator. Dog’s with ovarian remnant syndrome may have normal hormone levels.
  • Ultrasound – Ultrasounds are sometimes used to enable vets to see the remnant. However, the remnant might be too small to be seen on the ultrasound. The accuracy of this test is dependent on the size of the remnant, the stage of heat the dog is in, and the ultrasound technician’s skill.
  • Hormone Stimulation Test – This is the most reliable test for diagnosing ovarian remnant syndrome. An artificial hormone is given to your dog while they are in heat. Then their blood is tested a week later. If the test shows increased progesterone levels then there is indeed a remnant. 


If your dog is diagnosed with ovarian remnant syndrome they will need to have the remaining tissue removed to prevent further heat cycles. 

Some argue that you should just leave it in place. After all, the dog can’t get pregnant without a womb. 

While that is true, spaying is beneficial to your dog’s health outside of pregnancy. 

A properly spayed dog has no risk of ovarian or uterine cancer, reduced risk of mammary cancer, reduced risk of pyometra, and is less prone to trying to escape the house during its heat. (Bitches go crazy for boy dogs when they come into heat!) 

Any ovarian tissue that still remains in your dog is at risk of becoming cancerous or getting infected. Then, of course, there’s the fact that the tissue triggers estrogen production which causes her to come into heat. 

A dog in heat can often be more scared or unpredictable. It’s also a bit of a messy situation that requires a lot of cleaning up! 

No, overall, it’s best to get the remaining ovarian tissue removed. 

You might be hesitant to put your dog through another operation but it is better for her in the long run. 

The vet will reopen the previous operation site and remove the ovarian tissue. The success of the operation does depend on how big the tissue is and how easy it is to access. 

Your vet might choose to do the operation when your dog is in heat. This is because that particular bit of tissue will be swollen and therefore easier to see. 


The recovery time will be similar to the first operation. They will need to take it easy for about two weeks and may need to wear a cone to stop them from licking the wounds. 

Once the tissue is removed, they will stop going into heat. They will also have all the benefits of spaying including the elimination of the risk of uterine and ovarian cancer. 

Final Thoughts

When we get our dog’s spayed we do so with the understanding that all of the uterus and ovaries are removed.

However, sometimes it can be very difficult to spot ovarian tissue. It is small and often indistinguishable. 

Luckily the condition is not life-threatening or serious and it can be corrected easily enough. 

If you ever notice a bloody discharge from a spayed dog, you should seek veterinary treatment immediately. 

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