Modernizing spay practice for females

A comparison of ovariohysterectomy and ovariectomy

In North America, having your dog or cat spayed means having its ovaries and uterus removed (called an ovariohysterectomy or OVH). However, in some European countries only the ovaries are removed (an ovariectomy or OVE). Why has OVE replaced OVH as the standard spay procedure for female pets in Europe but not the US and Canada?

By removing the uterus as well as the ovaries, a complete ovariohysterectomy is thought to remove any chance of future uterine pathology. North American veterinarians are likely responding to this concern as well as relying on their experience – OVH is the only method taught in most US veterinary schools. But studies conducted over 15 years ago found no evidence of increased health risks with OVH as compared to OVE (Okkens et al., 1997).

According to a 2006 review article, comparisons of the two procedures require considering immediate (post-surgical) issues as well as long-term health. Removal of only the ovaries is a quicker, less involved surgery that has fewer post-surgical problems and is not associated with long-term health problems (Van Goethem et al., 2006). The authors indicate that OVH may be associated with post-surgical hemorrhage, vaginal bleeding, obstruction of the ureter, ovarian remnant syndrome (which may occur less frequently with OVE) and uterine stump granulomas. However, a more recent publication found no difference between the two procedures in terms of surgical time, pain scores or wound healing scores (Peeters & Kirpensteijn, 2011).


Long-term health issues have traditionally been a concern when leaving the uterus intact with the OVE method, but data do not indicate that there are many differences between methods. Intact female dogs have approximately a 15-24% risk of developing pyometra, a disease of the uterus believed to be caused by progesterone and bacterial infection. If all of the ovarian tissue is removed and no piece is missed, pyometra does not occur and there is no more risk for it after OVE than after OVH. Uterine tumors are quite rare, occurring in only about 0.03% of dogs while only 0.003% are malignant. Since uterine tumors are strongly linked to hormonal influence, no higher incidence in dogs with OVE has been reported compared to OVH. No conclusive difference has been measured for the development of incontinence or weight gain following OVE or OVH.

A 2011 review by Del Toro and McArthy of OVH and OVE procedures concluded that there is no benefit to performing OVH over OVE, and advantages of OVE include the potential for less post-surgical issues. They note that when post-surgical problems do occur, they are likely related to inexperienced surgeons and/or larger dog size, not the particular procedure used. Importantly, the authors point out that minimally invasive techniques – like laparoscopy – are also becoming more widespread for spaying dogs and cats. Laparoscopic methods are easier with OVE and results in in less post-operative pain than open surgery, although laparoscopy is more expensive due to the specialized equipment required (see additional info below).

While OVH and OVE may have similar outcomes under controlled conditions, a simpler procedure like OVE will likely be the better choice for less experienced veterinarians or those who do not perform many spay operations. Access to the female reproductive tract can be made via the side of the body (flank) instead of the abdomen. These “flank spays” may be most useful for feral populations because the incision is easier to monitor from a distance and is less likely to become infected since it is not in contact with the ground (see additional info below). Parsemus Foundation encourages additional conversation and critical evaluation of spay procedures and collection of more comparable data to determine the best option. Be sure to review our page on ovary-sparing spay for more information on that alternative sterilization procedure.

OVH and OVE references

Erhardt E. 2012. Performing ovariectomy in dogs and cats. Veterinary medicine. (a how-to guide for veterinarians with excellent references)

Kirpensteijn, J. 2008. Ovariectomy versus ovariohysterectomy. Is the eternal argument ended? Proceedings of the International SCIVAC Conference 2008. (full article)

Okkens AC, Kooistra HS, Nickel RF. 1997. Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches. J Reprod Fertil Suppl. 51:227-31. (abstract)

Netherton, S. 2013. Ovariectomy or ovariohysterectomy: Which way to spay? (general information)

The SkeptVet Blog. 2013. What is a spay? Ovariectomy vs. ovariohysterectomy for the female dog. (general information)

Laproscopic spay references

Culp WT, Mayhew PD, Brown DC. 2009. The effect of laparoscopic versus open ovariectomy on postsurgical activity in small dogs. Vet Surg. 38(7):811-7. (abstract)

Gower S, Mayhew P. 2008. Canine laparoscopic and laparoscopic-assisted ovariohysterectomy and overiectomy. Compend Contin Educ Vet 30(8):430-2, 434, 436, 438, 440. (abstract)

Lee JY, Kim MC. 2013. Comparison of oxidative stress status in dogs undergoing laparoscopic and open overiectomy. J Vet Med Sci (full article)

Flank spay references

Austin Humane Society Feral Cat Clinic. (general information)

Burrow R, Wawra E, Pinchbeck G, Senior M, Dugdale A. 2006. Pospective evaluation of postoperative pain in cats undergoing ovariohysterectomy by midline or flank approach. Vet Rec. 158:657-660. (abstract indicating flank approach may result in more postsurgical pain)

Coe RJ, Grint NJ, Tivers MS, Hotston Moore A, Holt PE. 2006. Comparison of flank and midline approaches to the ovariohysterectomy of cats. Vet Rec. 159:309-313. (abstract indicating little difference between approaches)