Ovarian Sparing Spay (OSS)

Ovarian Sparing Spay (OSS)
February 1, 2021

For decades, we in the veterinary community have performed ovariohysterectomies (spay) in female dogs for both population control and because we believed it was a preventative measure against potential medical conditions. Spayed dogs do seem to have fewer mammary tumors and pyometras, as well as no ovarian cysts or ovarian cancers. These health benefits, combined with population control, gave veterinarians confidence in performing spays.

Over time, we have begun to see that removing the ovarian hormones does come with some potential negative effects. Currently, there are studies showing that removing the ovaries, especially at a young age, increases the risks of:

  • mast cell tumors
  • hemangiosarcoma
  • osteosarcoma
  • transitional cell carcinoma
  • lymphoma
  • hip dysplasia
  • cranial cruciate ligament tears
  • urinary incontinence and bladder infection
  • hypothyroidism
  • diabetes
  • some fear and anxiety disorders
  • obesity

This is a long list of serious and often fatal disorders. While no one is suggesting that all of these conditions are always caused by spaying, and it is true that some dogs who have not been spayed end up contracting these diseases anyway, it is clear that we are increasing the risk of these conditions by our standard spay procedure, especially when it is performed on young puppies.

So, what can or should we be doing differently? The answer is complicated.  First, I want to be crystal clear that I am not being critical of people who perform standard spays in puppies. I still do them for some of the reasons that will be outlined below. Humane societies have been some of the biggest proponents of early spaying because of the huge problem that some areas have with puppy overpopulation. These societies have made great strides in reducing unwanted puppies, and at least in my region, the days when dogs were euthanized in large numbers simply because they had no home are mostly behind us. That is a good thing and those people working in those organizations are good people who have reduced a lot of animal suffering.  I only intend to give each owner all of the pertinent information surrounding this procedure so that each owner can make the best personal decision for their pet.

Some the problems listed can be reduced by leaving an ovary in place during the spay procedure. By removing the entire uterus, we eliminate unwanted pregnancies and the risk of pyometra, but by leaving one ovary, the patient still retains her hormones and continues to receive the positive benefits. These patients will statistically have better muscle tone, more healthy body fat percentages and maintain their mobility and enjoy increased life spans. They should also experience lower cancer rates for the deadly cancers listed above.

So why don’t we just adopt this as the “norm” for all patients? There are a few issues that may be a problem for many homes:

  • These patients will continue to experience estrus (a “heat” cycle). They should not have the bloody discharge, but they will be attractive to males and they may attempt to breed.
  • There will be an increased number of mammary tumors. Not all of these are malignant, but they can be and even the benign ones can grow large and cause problems.  Mammary tumors may require surgery when or if they occur.
  • Rare problems that could occur also include ovarian tumors or cysts and vaginal hyperplasia and vaginal prolapse.
  • An ovarian sparing spay requires a larger incision and takes a little more time and materials, meaning it costs a little more to perform.

Many people are not comfortable with a dog who will cycle or possibly experience these other medical issues later in life. For these owners, a traditional spay is still comfortable, familiar, and is certainly an acceptable choice.

For owners who have become educated about the potential benefits of ovarian sparing surgery and feel that it is the best option for their pet in their home and environment, this is a great option and we are happy to be able to share this information and offer it as a choice for our patients.

This article is an overview and not intended to be a thorough review of the literature. For further reading, we suggest: