At first glance, the terms "ovariohysterectomy" and "ovariectomy" look similar enough that you might think they refer to the same procedure, but that is not the case.
An ovariohysterectomy (OHE) is what we think of as a traditional spay where both ovaries and the uterus down to about the level of the cervix is removed. An ovariectomy (OE) is simply the removal of both ovaries while leaving the uterus in place.
In the United States, the OHE has long been and still is the surgery of choice when it comes to eliminating a female dog or cat’s ability to reproduce and preventing some common diseases of the reproductive tract (e.g., uterine infections and breast cancer). This might be changing, however. In other parts of the world, the OE is the more common surgery as long as a pet’s uterus is healthy. More veterinarians in the US are starting to move in this direction too, which can lead to questions from owners who are not familiar with OE surgeries.
The main benefit of an OE versus an OHE is the ability to perform the surgery through a smaller incision. This incision can also be locate a little farther forward on the pet’s abdomen, which improves the surgeon’s ability to locate, manipulate, and surgically remove the ovaries. This could potentially reduce surgery times, surgical complications, and the amount of discomfort a pet feels postoperatively, although the few studies that have looked into these factors have not shown a significant difference between OEs and OHEs. This could change, however, as a greater number of surgeons become more familiar and practiced in OE techniques.
Owners are often concerned that leaving the uterus in place increases the chance that their pets could develop uterine disease in the future. The two biggest issues are pyometra and uterine cancer.
Pyometras can only develop in a dog that is under the influence of progesterone. Progesterone is made by the ovaries, so as long as both ovaries are completely removed and a dog is not treated with a medication containing progesterone (something which is almost never done), a pyometra will not occur. Relying on OHEs is not completely protective either. We can and do see something called a “stump” pyometra (i.e., infection involving the small part of uterus that remains after an OHE) when a piece of ovarian tissue is mistakenly left behind during surgery or progesterone is supplied exogenously.
Uterine tumors are very rare in dogs and cats, and they also seem to be under hormonal influence. Therefore, removing a pet’s ovaries at a relatively early age should even further reduce the chances of their forming if the uterus is left in place. The most common type of uterine tumor is a leiomyoma, which is benign, so in the unlikely event that one should form, removing the uterus at that time should be curative.
What this all boils down to is that both OHEs and OEs can be an effective form of surgical sterilization, but the OE may have some potential benefits, particularly when performed by an experienced surgeon. Dr. Jennifer Coates