Spaying has become such a standard practice that many of us don’t give it a second thought. We know it’s absolutely necessity to help stem pet overpopulation. In fact, spaying has been the key factor in reducing the number of euthanized dogs and cats from 23.4 million in 1970 to just under 3 million now. But what if you could offer your clients a way to maintain that progress, while honoring your commitment to do what is best for each patient’s health?

Thought leaders are beginning to accept that spay and neuter have both positive and negative health consequences that vary by age, gender and breed. In 2007, veterinarian Dr. Margaret Root Kustritz published a review of the pros and cons of spaying and neutering at different ages (“Determining the optimal age for gonadectomy of dogs and cats”, JAVMA). That same year, a review paper entitled “Long-Term Health Risks and Benefits Associated with Spay/Neuter in Dogs” (Sanborn LJ, available online) gathered the data and summarized it in a comprehensible form.

Implications for large breeds

The conclusion? Mounting evidence indicates that in large dogs at least, the health benefits of keeping the ovaries may outweigh the health risks, which include mammary tumors and infection of the uterus. For example, removing the ovaries of a Rottweiler quadruples her risk of bone cancer — spayed Rottweilers have a frighteningly high one in four risk of osteosarcoma. Spaying also raises her risk of hemangiosarcoma to 10% to 20%. In addition, traditional spay impacts quality of life issues. The loss of ovarian hormones increases the risk of CCL tears, incontinence, and an obsession with food that can lead to weight gain.

As a result, informed pet owners are beginning to question or resist spay surgery. Those adopting breeds known to have greater risk of certain problems after spay may be in this category (for example, boxers nearly always get incontinence, and giant breeds are prone to bone cancers). This is a distressing development for shelters, which fear a renewed increased in the overpopulation and euthanasia rates formerly curtailed by spay/neuter operations.

The Parsemus Foundation, a non-profit that promotes evidence-based medicine and choice for animal health, is proposing that we all think more creatively about individualizing spay operations. In the situations mentioned above, veterinarians should be prepared to remove the dog’s uterus and leave the ovaries in a procedure that’s sometimes called “partial spay.”

Remove the uterus, leave the ovaries

Removing the uterus eliminates the nuisance of bleeding during heats, along with the risk of infection of the uterus (pyometra), as long as all the uterus is removed. However, precise technique is essential. In traditional spay, there is no need to remove every bit of the uterus, since it will no longer be under stimulation by the ovaries. But in partial spay, also known as ovary-sparing spay, the veterinarian must make a large enough incision to pull the uterus up to the surface, see what he/she is doing, and be able to tie off and cut precisely at the cervix rather than just anywhere on the uterus. Otherwise, it is still possible to have an infection develop in the remaining uterine stump (“stump pyometra”). With this technique, the risk of stump pyometra is eliminated.

If the whole uterus is removed, mammary tumors are the only significant health risk remaining from a partial spay. Ovarian cancer is rare enough that the ovaries should not be removed just to try to prevent it. Clients who feel their dogs are likely to live longer or stay healthier by retaining their ovaries can then be informed of the pros and cons, and advised to stay alert to the possibility of mammary tumors as their dogs age.

A video demonstration

The Parsemus Foundation has funded a demonstration of ovary-sparing spay by Dr. Michelle Kutzler, a professor of veterinary medicine at Oregon State University and an acknowledged expert and speaker on dog and cat contraceptive advances and reproduction. In the video on the foundation’s website (, Dr. Kutzler demonstrates ovary-sparing spay in a six-year-old mastiff who was finished breeding but whose owner was concerned about her increased risk of bone cancer and cruciate ligament rupture from traditional ovariohysterectomy spay.

As Dr. Kutzler demonstrates in the video, the cervix must be ligated precisely — one cannot ligate just anywhere on the uterus as is normally done — to prevent the risk of stump pyometra. This fine point is what has kept ovary-sparing spay from being considered a widespread option. Dr. Kutzler points out that the solution lies in taking extra care with ligation placement. Her slightly larger incision allows her to visualize the area and take this extra care.

Benefits for veterinary practice

  • Owners with the economic means may even wish to have a mammary-gland ultrasound as part of their dogs’ annual exams once the animals reach middle age; veterinarians who are skilled with ultrasound should be pleased at the opportunity to offer this new service using existing equipment. Meanwhile, population goals are also achieved, because a dog will not be fertile without a uterus.
  • The procedure takes slightly longer than high-volume spay, because the cervix must be cut and tied off precisely and a larger incision must be made to see what one is doing. More suture time is involved. In compensation, veterinarians offering this option will be able to both meet the needs of a highly-informed group of clients, and distinguish their value-added services from high-volume discount spay.
  • Currently, only three veterinarians in the United States are offering ovary-sparing spay. This means that those who learn the procedure will likely be able to command a substantial premium, with new clients willing to travel a significant distance to obtain the procedure for their dogs.
  • The Parsemus Foundation has begun a list on its website of veterinarians performing hysterectomy (ovary-sparing spay) as an alternative to ovariohysterectomy. Veterinarians who learn the technique from the demonstration video (see additional sidebar for more info) and decide to add it to their services can contact the foundation to be included on this list [callout] …removing the ovaries of a Rottweiler quadruples her risk of bone cancer — spayed Rottweilers have a frighteningly high one in four risk of osteosarcoma. Elaine Lissner is director of the San Francisco-based Parsemus Foundation, which works to advance innovative and neglected medical research. The foundation’s focus is on supporting small proof-of-concept studies and then pursuing press coverage of the results, so that advances change treatment practice rather than disappearing into the scientific literature. In addition to providing a training video for ovary-sparing spay, the foundation is also working to raise the level of evidence on calcium chloride nonsurgical male dog and cat sterilization, so veterinarians can make an informed decision on best practices and potential risks. The foundation’s work has been featured in WIRED, BBC News, Scientific American, and The Wall Street Journal.

For individuals seeking a veterinarian to perform procedures beyond surgical spay or neuter, view a list of providers here.

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