A standard spay is not a hysterectomy. The most common spay procedure in dogs and cats removes both the ovaries and the uterus, making it an ovariohysterectomy. A hysterectomy, by contrast, removes only the uterus while leaving the ovaries in place. That distinction matters because the ovaries produce the hormones that drive heat cycles, behavior changes, and certain disease risks.
What a Standard Spay Actually Removes
When most veterinarians in the United States perform a spay, they remove both the ovaries and the uterus in a single surgery called an ovariohysterectomy. This eliminates the organs that produce reproductive hormones (estrogen, progesterone, and testosterone) along with the uterus itself. The result is permanent sterilization, the end of heat cycles, and the removal of any risk of uterine infection.
In many European countries, the standard approach is an ovariectomy, which removes only the ovaries and leaves the uterus behind. Without ovarian hormones stimulating it, the remaining uterus shrinks and becomes inactive. Studies comparing the two approaches have found no increased risk of uterine infection (pyometra) after ovariectomy alone, which is why European veterinarians consider it equally safe with a slightly smaller surgical footprint.
How a Hysterectomy Differs
A true hysterectomy in a dog removes the uterus but leaves the ovaries intact. In veterinary medicine, this is sometimes called an ovary-sparing spay. It prevents pregnancy and eliminates the risk of pyometra, a life-threatening uterine infection. But because the ovaries stay, the dog continues producing sex hormones. That means she will still go through heat cycles, with the associated behavioral signs and vulvar swelling, even though she cannot become pregnant.
Some owners specifically choose this option. In a survey published in the Journal of the American Veterinary Medical Association, 65% of owners who opted for an ovary-sparing spay or vasectomy believed the procedure resulted in a healthier dog. Their primary motivations were preventing breeding (39%) and eliminating the risk of pyometra (47% of female dog owners). The logic is straightforward: keep the hormones that may benefit joints, metabolism, and behavior while still preventing reproduction and uterine disease.
Why Hormones Are the Key Difference
The ovaries are the main source of estrogen, progesterone, and testosterone in female dogs. A standard spay dramatically reduces all three. Research measuring hormone levels after ovariohysterectomy found that urinary testosterone dropped sharply and progesterone fell from about 4.16 to under 1.74 pmol/mmol creatinine, staying low indefinitely. This hormonal shift is what stops heat cycles and contributes to the disease-prevention benefits of spaying.
It is also what causes some of the recognized side effects. Without estrogen, about 5% of spayed female dogs develop urinary incontinence. The risk is heavily skewed toward larger dogs: those over 33 pounds (15 kg) are roughly seven times more likely to become incontinent than smaller dogs. This side effect doesn’t occur with an ovary-sparing hysterectomy because estrogen levels remain normal.
Cancer Prevention Depends on Ovary Removal
One of the biggest health arguments for a traditional spay is mammary cancer prevention, and that benefit comes entirely from removing the ovaries, not the uterus. The timing matters enormously. Dogs spayed before their first heat cycle retain only about 0.5% of the mammary cancer risk compared to intact dogs. After one heat cycle, that figure rises to 8%. After two or more cycles, it jumps to 26%.
An ovary-sparing hysterectomy does not provide this protection. Because the ovaries continue producing estrogen, mammary tissue remains exposed to the same hormonal stimulation as in an intact dog. Owners choosing this route should be aware that regular mammary checks become just as important as they would be for an unspayed dog.
Recovery Is Similar for Both
Whether a dog undergoes a standard spay or an ovary-sparing hysterectomy, the recovery timeline looks much the same. Expect your dog to be groggy, possibly nauseous, and a bit wobbly for the first 24 hours. Appetite typically returns within 48 hours. The critical window is the first 10 to 14 days, during which your dog needs strict exercise restriction: no running, jumping, or rough play. Strenuous activity can cause swelling around the incision, premature dissolving of sutures, or the incision opening entirely.
During this period, keep the incision dry (no baths or swimming) and check it twice a day for redness, swelling, or discharge. An Elizabethan collar, the classic cone, is the most reliable way to stop your dog from licking or chewing at the site and should stay on for the full 10 to 14 days.
Which Procedure Is Right for Your Dog
For most pet owners, a standard spay (ovariohysterectomy) remains the most practical choice. It eliminates heat cycles, prevents pregnancy, removes the risk of uterine infection, and provides significant mammary cancer protection when done early. It is the default procedure at virtually every veterinary clinic in the United States.
An ovary-sparing hysterectomy makes sense for owners who want to preserve their dog’s hormonal balance, particularly in breeds prone to joint disorders or other conditions that may be influenced by early hormone loss. The trade-off is ongoing heat cycles and no reduction in mammary cancer risk. This procedure is less widely available and typically performed by veterinarians who specialize in minimally invasive surgery.
An ovariectomy, removing only the ovaries, offers the same hormonal and cancer-prevention benefits as a full spay with a somewhat smaller incision. It is standard in Europe and gaining popularity in the U.S., though many American veterinarians still default to removing both organs.