Presentation on Surgical Neutering Techniques

Here are the notes and slides for a presentation I recently gave comparing various surgical sterilization and neutering techniques.

Among the most common surgical procedures in small animal practice are those for sterilization (preventing reproduction) and neutering (removing the gonads). The goal of these procedures is both to prevent reproduction and to provide a net health benefit for the patient. This benefit 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 which we can use to make rational decisions about our choice of technique. We can also use this research to inform the recommendations we make to clients. Pet owners are increasingly aware that there are multiple alternatives to choose from, and they may come to us with strong opinions or misconceptions about the most appropriate procedure to 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 quite variable. There is much less evidence for a net health benefit in neutering males, though there are other justifications for doing so. Today I will consider the relative advantages and disadvantages of different surgical sterilization methods for males and females.

The most common spay procedure in the United States is ventral midline ovariohysterectomy (OVH). This is an effective technique for sterilization and neutering of both dogs and cats with very low complications rates when performed by experienced surgeons.4-6 There are many minor variations with no research evidence comparing the relative merits of most.

One exception is the flank approach to ovariohysterectomy, 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 the flank approach is faster with fewer complications,7 but other studies find no difference8, and some indicate more discomfort associated with the flank approach.9-10 Access to both ovaries is more difficult with the flank 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, ovariohysterectomy has been preferred in the United States 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 post-operative pain or other complications.10,16

A relatively recent option is the laparoscopic spay. Both laparoscopic ovariectomy and ovariohysterectomy 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 post-operative pain, complications, and recovery time, though the literature is not consistent and there is a lack of high-quality studies.21

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 (sometimes called an “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.

Despite the uncertainties, surgical neutering is the most common approach to sterilization of male cats and dogs. For dogs, frequently used techniques include closed castration (removal of the testes without opening the vaginal tunic) and open castration (which involves opening the vaginal tunic prior to ligating the vessels and ductus deferens). Both procedures can be performed through a scrotal or pre-scrotal incision, and there are a number of variations of each.

There is much debate about the relative merits of open and closed castration in dogs, but it is based mostly on theoretical reasoning and anecdotal evidence. Some argue that closed castrations are safer because there is no direct communication with the abdomen, reducing the risk of ascending infections or herniation of abdominal contents. Others claim that open castrations are less likely to lead to hemorrhage or scrotal hematomas. Typically, closed castration is recommended for small dogs and cats and open castration for larger dogs.

There is little research evidence to inform these debates. One prospective randomized trial did find more overall complications in dogs undergoing open castration.24 However, problems with recruitment of subjects for this study significantly limit the strength of this evidence. Overall, serious complications are few in dogs undergoing castration, and it is unclear if there is a consistent advantage to either technique.

The research evidence comparing scrotal and pre-scrotal approaches in dogs is also quite sparse. A randomized, prospective study comparing the two approaches found similar complication rates.25 The scrotal approach had the advantage of inducing less self-trauma and of being about 30% quicker to perform (though the absolute difference, from about 5 minutes to 3 minutes, is of doubtful clinical significance). Once again, both techniques are effective, and it is not clear that one is superior to the other.

Several techniques have been described for neutering male cats,26 but there is virtually no formal research comparing complication rates. A scrotal approach appears to be the most common, and methods for securing the ductus and vessels include suture ligation and various methods of tying the tissues on themselves. One comparative study of these ligation methods found no significant complications and no difference between methods.27

An uncommon surgical technique used for male dogs in some resource-poor countries is pinhole castration. The spermatic cord is ligated with suture percutaneously to induce necrosis of the testes.28 While this technique is less expensive than standard surgical castration and it does reduce functional testicular tissue volume, it is unclear how effective it is as a means of sterilization, and some reports suggest a higher rate of infection, pain, and other complications compared with standard techniques.29-30

Finally, surgical or laparoscopic vasectomy is sometimes recommended as a means of sterilizing male dogs and cats without neutering.26 Both approaches are effective at achieving this outcome. There have been no direct published comparisons between surgical and laparoscopic vasectomy. One small study comparing laparoscopic vasectomy with surgical castration in dogs found few differences except for a subjectively greater level of post-operative discomfort in the surgical patients.31


  1. 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.
  2. 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:
  3. May S. The flank cat spay: eminence-driven fashions in veterinary surgery. Veterinary Record. 2012;170:460-461.
  4. Howe LM. Surgical methods of contraception and sterilization. Theriogenology. 2006 Aug;66(3):500-9.
  5. 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.
  6. 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
  7. 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
  8. 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
  9. 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.
  10. 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.
  11. Janssens LA. Janssens GH. 1991. Bilateral flank ovariectomy in the dog—surgical technique and sequelae in 72 animals. Journal of Small Animal Practice. 32: 249– 252.
  12. 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.
  13. DeTora M. McCarthy R. J. 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: 110
  14. Okkens AC. Kooistra HS. Nickel RF. Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches. Journla of Reproduction and Fertility Suppl 1997;51:227–31.
  15. 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
  16. 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.
  1. Davidson EB. Moll HD. Payton ME. Comparison of laparoscopic ovariohysterectomy and ovariohysterectomy in dogs. Veterinary Surgery. 2004;33:62–69.
  2. 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.
  3. Gower S. Mayhew P. Canine laparoscopic and laparoscopic assisted ovariohysterectomy and ovariectomy. Compendium of Continuing Education for the Practicing Veterinarian. 2008;30:430–440.
  4. 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.
  5. Phypers C. In Cats and Dogs Does Laparoscopic Ovariectomy Offer Advantages Over Open Ovariectomy for Postoperative Recovery?. Veterinary Evidence. 2017; 2(2). doi:
  6. Grier RL. Tubal ligation-alternative sterilization operation. Iowa State University Veterinarian. 1973;35(2):49-50
  7. Belfield WO. Partial spay (hysterectomy). Veterinary Medicine. 1972;1223-1224.
  8. Hamilton KH. Henderson ER. Toscano M. et al. Comparison of postoperative complications in healthy dogs undergoing open and closed orchidectomy. J Small Anim Pract. 2014 Oct;55(10):521-6.
  9. Woodruff K. Rigdon-Brestle K. Bushby, PA. et al. Scrotal castration versus prescrotal castration in dogs. Vet Med. 2015;110(5):131-135.
  10. Howe LM. Surgical methods of contraception and sterilization. Theriogenology. 2006 Aug;66(3):500-9. Epub 2006 May 23.
  11. Karen Maciel de Oliveira, Leonardo Augusto Lopes Muzzi, Bruno Benetti Junta Torres, et al. A comparative study among three open orchiectomy techniques in cats. Acta Scientiae Veterinariae. 2010;38(2):177-183.
  12. Okwee-Acai J. Omara R. Onyait JS. et al. evaluation of pinhole castration as an alternative technique for dog population control in resource-poor communities. Bulletin of Animal Health and Production in Africa An. 2013;61(3):337-345.
  13. Baba MA, Fazili MR, Athar H, et al. Pinhole castration technique: an alternative to orchiectomy in stray dogs. Anim Reprod Sci. 2013;137(1-2):113-8.
  14. Abd-el-Wahed RE. Korritum AS. Abu-Ahmed al. Evaluation of pinhole castration technique compared with traditional method for castration in dogs. Alexandria Journal of Veterinary Sciences. 2014;42:90-98.
  15. Anburaja Mahalingam; Naveen Kumar; Maiti S.K. et al. Laparoscopic sterilization vs. open method sterilization in dogs: a comparison of two techniques. Turkish Journal of Veterinary & Animal Sciences. 2009;33(5):427-436.


OVE, OVH, OMG: Pragmatic Review of Surgical Neutering Techniques Slides

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5 Responses to Presentation on Surgical Neutering Techniques

  1. nomipalony says:

    thank you it really worked

  2. Fernando says:

    Any benefits to vasectomy over neutering? And do you have any article on when to neuter a dog? Thanks.

  3. skeptvet says:

    Vasectomy is essentially the same as not neutering except that it prevents reproduction, so the pros and cons are almost the same as leaving the dog intact.

    Timing is a complex subject without any simple rules-of-thumb. Here is the full collection of my articles and lit reviews on neutering if you want to look at the sections addressing that subject.

  4. Robin says:

    Is there any benefit to removing the uterus and cervix but leaving the ovaries? I was told by my vet that the ovaries will still release some hormones that my dog needs and will reduce the risk of cancer and other hormonal issues. What are your thoughts?
    Thank you!

  5. skeptvet says:

    Leaving the ovaries is functionally equivalent to not spaying the dog at all. It may prevent pyometra (uterine infections), but it has no effect on any of the other conditions influenced by neutering. As you will see from the many, many articles here on the subject, exactly what those risks and benefits are and what the best choice is for any individual dog is complex, and no one can say with any justifiable certainty what will happen to your specific dogs. In general, not removing the ovaries increases the risk of breast cancer. It may reduce the risk of some cancers in some breeds, mostly large breed dogs with an already elevated risk of those types of cancer, but in many dogs this will not be the case. The latest review found no effect on cancer risk in small breeds (except Shih-tzu’s), and even Labradors and golden retrievers react differently, so no universal, one-size-fits-all rule is going to work.

    On balance, most dogs will likely live longer and have fewer serious health problems if they are neutered, though it may benefit larger breeds to wait until full growth (12-14 months). I would encourage you to spend some more time looking at thee research because your vet’s recommendation is not what the vast majority of vets have concluded is the best approach.

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