Among the most common surgical procedures in small animal practice are those for sterilization and neutering. The goal of these procedures is both to prevent reproduction and to provide a net health benefit for the patient that may include avoiding the risks of reproduction, reducing the incidence of those disease that are more common in intact animals, and reducing behaviors associated with intact status that can lead to relinquishment.1-2 There are many variations on these procedures, and the specific techniques used by individual veterinarians seem to depend more on tradition, personal habit, and cultural preference than on explicit evaluation of the pros and cons from a scientific perspective.3 There is, however, research evidence concerning some of these procedures that we can use to make rational decisions about our choice of technique. We also can use this research to inform the recommendations we make to clients. Pet owners increasingly are aware that multiple alternatives exist, and they may come to us with strong opinions or misconceptions about the most appropriate procedure for their pets. Most procedures are intended to prevent reproduction. Some also involve gonadectomy, which has a complex array of both beneficial and harmful effects that depend on breed, sex, age, timing of surgery, and many other factors. The long-term pros and cons of gonadectomy are controversial, and I have reviewed them in detail elsewhere.2 In brief, there appears to be a net health benefit for most female dogs and cats from neutering, though the details of the risks and benefits and the effect of the timing of neutering are variable. There is much less evidence for a net health benefit in neutering males, though there are other justifications for doing so. Here I will consider the relative advantages and disadvantages of different surgical sterilization and neutering options for females. The most common U.S. spay procedure Ventral midline ovariohysterectomy (OVH) is considered an effective technique for sterilization and neutering of both dogs and cats with very low complication rates when performed by surgeons that are experienced with this procedure.4-6 There are many minor variations with no research evidence comparing the relative merits of most. One exception is the flank approach to OVH, which is preferred in some countries for cats and small dogs. There are theoretical advantages and disadvantages to this approach, and research evidence comparing flank and midline approaches is mixed. Some comparisons suggest it’s faster with fewer complications,7 but other studies find no difference,8 and some indicate more discomfort associated with it.9-10 Access to both ovaries is more difficult with this approach unless bilateral flank incisions are made, which significantly complicates the procedure, and hysterectomy can be difficult by this method.11 The flank and midline methods both achieve the goal of gonadectomy and sterilization. Traditionally, OVH has been preferred in the U.S., while ovariectomy (OVE) is the more common choice in some other countries.12 Both techniques are equally effective at achieving gonadectomy and preventing mammary carcinoma and pyometra.12-14 Some studies have suggested that OVE is less painful than OVH15; however, other studies have not identified any difference in postoperative pain or other complications.10,16 A relatively recent option Laparoscopic OVE and OVH have been reported using a variety of equipment and techniques. Comparisons are difficult given the many different approaches, equipment, and assessments used in published studies. In general, the disadvantages of laparoscopic OVE and OVH include the cost of equipment, the need for extensive training and practice to achieve proficiency, and the longer surgical time.17-20 Laparoscopic spay may have the advantage of decreasing postoperative pain, complications, and recovery time, but the literature is inconsistent, and high-quality studies are lacking.21 Tubal ligation and hysterectomy With a growing awareness of the potential negative effects of neutering, there has been some increased interest among breeders and pet owners in sterilization procedures that do not involve gonadectomy. For females, two such procedures are hysterectomy (or ovary-sparing spay) and ligation of the fallopian tubes or uterine horns. Both procedures have been described in the literature,22-23 but neither have been widely adopted. There are no controlled research studies comparing tubal ligation or hysterectomy to OVE or OVH. While ligation of the fallopian tubes or uterine horns can prevent reproduction, it is highly likely that any risks and benefits associated with the presence of ovaries2 are the same for females having a tubal ligation as for those not spayed at all. A complete hysterectomy, including removal of the cervix, likely eliminates the concern for pyometra, while the other risks and benefits of intact status remain unchanged. The bottom line OVH and OVE are equally effective methods of neutering. OVE may be slightly quicker and cause less postoperative discomfort. A flank approach can be used for OVE and OVH in cats and small dogs, though there is some evidence that it’s more painful than a ventral midline approach and may be more technically challenging for OVH or for larger patients. Laparoscopic spay techniques also are effective, and these may cause less discomfort that open techniques. However, laparoscopy requires expensive equipment and specialized training and typically takes longer than an open spay. Tubal ligation and hysterectomy are uncommon techniques that can prevent reproduction without neutering. However, these procedures are equivalent to not spaying at all with regard to most health effects and do not accomplish most of the goals of spaying female dogs and cats. The most appropriate spay procedure for a specific dog or cat must be determined by individual circumstances and in consultation with the owner. The existing evidence suggests that the most common procedures, ventral midline OVH and OVE, are safe and effective in achieving the goals of spay for most pets. Other procedures can be considered in select cases and with an awareness of their relative advantages and disadvantages. A thorough understanding of the options and the risks and benefits of each can help us to effectively counsel and educate our clients. Dr. McKenzie discovered evidence-based veterinary medicine after attending the University of Pennsylvania School of Veterinary Medicine and working as a small animal general practice veterinarian. He has served as president of the Evidence-Based Veterinary Medicine Association and reaches out to the public through his SkeptVet blog, the Science-Based Medicine blog, and more. He is certified in medical acupuncture for veterinarians. References New JC. “Characteristics of shelter-relinquished animals and their owners compared with animals and their owners in U.S. pet-owning households.” Journal of Applied Animal Welfare Science 2000; 3(3):179–201. McKenzie B. “Evaluating the benefits and risks of neutering dogs and cats.” CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources. 2010; 5(45):1-18. Updated version available at https://goo.gl/pWCKYl. May S. “The flank cat spay: eminence-driven fashions in veterinary surgery.” Veterinary Record. 2012;170:460-461. Howe LM. “Surgical methods of contraception and sterilization.” Theriogenology. 2006 Aug; 66(3):500-9. Berzon JL. “Complications of elective ovariohysterectomies in the dog and the cat at a teaching institution: clinical review of 853 cases.” Veterinary Surgery. 1967;8:89–91. Burrow R, Batchelor D, Cripps P. “Complications observed during and after ovariohysterectomy of 142 bitches at a veterinary teaching hospital.” Veterinary Record 2005;157:829–833. Kiani FA, Kachiwal AB, Shah MG, et al. “Comparative Study on Midline and Flank Approaches for Ovariohystrectomy in Cats.” Journal of Agriculture and Food Technology. 2014;4(2):21-31. Coe RJ, Grint NJ, Tivers MS, et al. “Comparison of flank and midline approaches to the ovariohysterectomy of cats.” Veterinary Record. 2006;159(10):309-313. Oliveira JP, Mencalha R, dos Santos Sousa CA, et al. “Pain assessment in cats undergoing ovariohysterectomy by midline or lateral celiotomy through use of a previously validated multidimensional composite pain scale.” Acta Cirúrgica Brasileira. 2014;29(10):633-38. Burrow R, Wawra E, Pinchbeck G, et al. “Prospective evaluation of postoperative pain in cats undergoing ovariohysterectomy by a midline or flank approach.” Veterinary Record. 2006;158(19):657-60. Janssens LA, Janssens GH. “Bilateral flank ovariectomy in the dog—surgical technique and sequelae in 72 animals.” Journal of Small Animal Practice. 1991;32:249– 252. Van Goethem B, Schaefers-Okkens A, Kirpensteijn J. “Making a rational choice between ovariectomy and ovariohysterectomy in the dog: a discussion of the benefits of either technique.” Veterinary Surgery. 2006;35(2)136-143. DeTora M, McCarthy RJ. “Ovariohysterectomy versus ovariectomy for elective sterilization of female dogs and cats: is removal of the uterus necessary?” Journal of the American Veterinary Medical Association. 2011;239:110. Okkens AC, Kooistra HS, Nickel RF. “Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches.” Journal of Reproduction and Fertility Supply. 1997;51:227–31. Lee SS, Lee SY, Park S, et al. “Comparison of ovariectomy and ovariohysterectomy in terms of postoperative pain behavior and surgical stress in dogs.” Journal of Veterinary Clinics. 2013;30(3)166-171. Peeters ME, Kirpensteijn J. “Comparison of surgical variables and short-term postoperative complications in healthy dogs undergoing ovariohysterectomy or ovariectomy.” Journal of the American Veterinary Medical Association. 2011:238;189-194. Davidson EB, Moll HD, Payton ME. “Comparison of laparoscopic ovariohysterectomy and ovariohysterectomy in dogs.” Veterinary Surgery. 2004;33:62–69. Ataide MW, de Brun MV, Barcellos LJ, et al. “Laparoscopic-assisted or open ovariohysterectomy using Ligasure AtlasTMin dogs.” Ciência Rural. 2010; 40(9):1974-1979. Gower S, Mayhew P. “Canine laparoscopic and laparoscopic assisted ovariohysterectomy and ovariectomy.” Compendium of Continuing Education for the Practicing Veterinarian. 2008;30:430–440. Case JB, Boscan PL, Monnet EL, et al. “Comparison of surgical variables and pain in cats undergoing ovariohysterectomy, laparoscopic-assisted ovariohysterectomy, and laparoscopic ovariectomy.” Journal of the American Animal Hospital Association. 2015;51(1):1-7. Phypers C. “In Cats and Dogs Does Laparoscopic Ovariectomy Offer Advantages Over Open Ovariectomy for Postoperative Recovery?” Veterinary Evidence. 2017; 2(2). doi: http://dx.doi.org/10.18849/ve.v2i2.59. Grier RL. “Tubal ligation-alternative sterilization operation.” Iowa State University Veterinarian. 1973;35(2):49-50. Belfield WO. “Partial spay (hysterectomy).” Veterinary Medicine. 1972;1223-1224.
