In veterinary medicine, one very common surgical procedure is the ovariohysterectomy, more commonly known as a spay. This procedure involves removing the ovaries and uterus down to the cervix to prevent a female pet from reproducing.
According to Dr. Heidi Phillips, a surgeon at the University of Illinois Veterinary Teaching Hospital in Urbana who specializes in urogenital and microsurgery, the traditional ovariohysterectomy is not the only way to safely sterilize a female pet.
"Another effective sterilization procedure for pets is the ovariectomy, in which the veterinarian surgically removes the ovaries and part of the uterine horn that is in close association with the ovary, but leaves most of the uterus," Phillips said.
So which is better?
Phillips said studies show these surgical techniques are equal in terms of achieving sterilization of the pet. The choice of procedure likely depends on what the surgeon has been trained to do.
Ovariohysterectomies are more commonly performed in the United States; it is the technique that is taught in veterinary colleges here, while ovariectomies are much more common in Europe.
Some advocate the ovariohysterectomy because of concern for a condition called stump pyometra, which occurs when fluid collects in what remains of the uterus after the surgery and causes severe infection. It has been suggested that removing the entire uterus to the cervix may help prevent this condition. However, stump pyometra results from hormone production from residual ovarian tissue, so removing the whole uterus is not necessary.
This was confirmed in a review of the literature published in Veterinary Surgery in 2006 by Dr. Bart van Goethem and co-authors, who concluded that ovariectomy will not increase the chance of developing a pyometra compared with ovariohysterectomy.
Removal of the entire uterus has also been advocated as a way to prevent uterine diseases, such as uterine cancer. However, according to Phillips, the incidence of uterine tumors in dogs and cats is very low. The review carried out by van Goethem and colleagues reports the incidence of uterine cancer in dogs makes up only 0.4 percent of all cancers in canines. Among the few animals that do develop uterine tumors, the majority of these tumors are benign.
Phillips also advocates the ovariectomy over the ovariohysterectomy because of the risk of complications associated with the latter procedure. She said that when the uterus is surgically removed along with the ovaries, the ureters — the tubes that convey urine from the kidneys to the bladder — can easily be damaged, either by becoming entangled in suture material or by being caught in a surgical clamp. Damage to a ureter could cause lifelong medical issues or even death for the animal.
"The greater risk and concern, in my opinion, is damaging the ureter during the more invasive surgical procedure," she said.
A third procedure, a laparoscopic spay, uses a minimally invasive approach to remove only the ovaries. For this surgery, a veterinarian uses a bipolar electrothermal vessel sealing device that can be used on the blood vessels of the ovaries and uterus and on the uterine horn. According to Phillips, performing a spay using devices that seal the tissue minimizes concern that bleeding could occur. The incision made is small, which may lead to a faster recovery, too.
In a study published in Veterinary Surgery in 2009 by Dr. William Culp and other veterinarians, dogs spayed laparoscopically showed more activity postoperatively than dogs spayed via the routine ovariectomy. But because it requires specialized training and instruments, few vets offer the laparoscopic spay.
For more information about ovariectomies, speak with your local veterinarian.
An archive of pet columns from the UI College of Veterinary Medicine is available at http://vetmed.illinois.edu/petcolumns/. Requests for reprints of this article may be directed to Chris Beuoy, email@example.com.