Ah, United States’ medicine vs. European medicine, the war rages on. The battleground I’ll discuss today: elective sterilization of the female reproductive tract.

This discussion came up in JAVMA recently, and I felt it warranted a look from a future vet. Granted I don’t have all the information and education here, but given that I’ve only ever seen ovariohysterectomy performed in practice, I’m interested in why we actually choose to remove the uterus as well.

Much of the article discusses the benefits gained from the simplicity of the ovariectomy procedure. With the potential to use laproscopic techniques, smaller incisions, and less manhandling of the abdominal cavity, post surgical pain and complications can be markedly reduced in both cat and dog patients. More specifically, better exposure of the ovarian pedicle due to the incision location allows for complete excision of the ovary, suggesting that the surgeon will be less likely to leave any remaining endocrine tissue.

Outside of the surgery itself, the authors discussed the often cited benefits of spaying companion animals, and how the two techniques alter the statistics. Unfortunately, there were little to no studies directly examining the incidence of these benefits when comparing groups with or without a uterus, and some of the numbers they did find were inconclusive or conflicting. I found it interesting to see some of the actual odds concerning the prevented conditions we advertize when discussing spays, the most common being mammary and uterine tumors.

The potential for mammary tumors seems to be the most significant of the spay benefits. Their overall incidence is 3.4%, with 41-53% being malignant (DeTora, 2011). If spayed before first estrus, that risk drops to 0.5%, which is huge! Almost all of the benefits from spaying come from the removal of sex hormone cycling, which seems to be largely necessary for many of these tumors to form (not surprising, as I had previously discussed how estrogen appears to have an immune boosting effect, which would promote chronic inflammation that we know to be an important risk factor for many cancers). The authors point out that as hormone cycling is prevented solely by removal of the ovaries, that all of the future medical benefits of sterilization are gained without removal of the uterus.

The only medical benefit correlated with sterilization that is obviously tied to removal of the uterus seems to be uterine neoplasia.  However, most uterine tumors are benign, with only 0.003% being malignant as well as easily treated with hysterectomy (DeTora, 2011). The authors also found no case of uterine neoplasia ever reported in a dog that had had its ovaries removed before 2 years of age, making this benefit of ovariohysterectomy moot.

While I do think that the authors wrote this commentary with an obvious preference for ovariectomy, the assumptions they made seem rational; and even though there wasn’t enough data to declare one technique superior to the other, I agree with the conclusion that the United States’ preference for ovariohysterectomy cannot be supported by the currently available evidence. However, there is no obvious disadvantage to the procedure, and whichever technique that specific surgeon is most proficient with will probably be the best choice in any situation.

DeTora M, & McCarthy RJ (2011). Ovariohysterectomy versus ovariectomy for elective sterilization of female dogs and cats: is removal of the uterus necessary? Journal of the American Veterinary Medical Association, 239 (11), 1409-12 PMID: 22087712