27 November 2020

Benefits and risks of neutering pets – what is the evidence – Effect of neutering on disease risk

spotlight topic: Benefits and risks of neutering pets – what is the evidence? Effect of neutering on disease risk Published 27 November 2020 | Updated 22 November 2024 While the effect of neutering on the risk of certain disease conditions has been known for a long time, particularly in terms of reducing disease directly associated with the reproductive tract, recent published evidence has provided more detailed evidence regarding the size of the effect and shown that the removal of reproductive hormones can have wide ranging effects on the body. While research papers normally report on the risks (positive and negative) of neutering in relation to a particular disease, it is important to consider the overall effect on the animal in terms of overall lifespan, which combine the risks from multiple causes. It is also important to be aware of confounding factors, such as age. Longevity

Michell, A.R. (1999) Longevity of British breeds of dog and its relationships with-sex, size, cardiovascular variables and disease. Veterinary Record, 145 (22), pp. 625-629 hhttps://dx.doi.org/10.1136/vr.145.22.625
Hoffman, J.M., Creevy, K.E. and Promislow, D.E. (2013) Reproductive capability is associated with lifespan and cause of death in companion dogs. PLoS ONE 8 (4), e61082 https://doi.org/10.1371/journal.pone.0061082
O’Neill, D.G. et al (2013) Longevity and mortality of owned dogs in England. The Veterinary Journal, 198 (3), pp. 638-643 https://doi.org/10.1016/j.tvjl.2013.09.020
O’Neill, D.G. (2015) Longevity and mortality of cats attending primary care veterinary practices in England. Journal of Feline Medicine and Surgery, 17 (2), pp. 125-133 https://doi.org/10.1177%2F1098612X14536176

Mammary tumours The beneficial effect of timing of spaying on the incidence of mammary tumours has been widely taught and accepted. However, for a long time this advice appears to have been based on evidence from a single paper published in 1969. A systematic review published in 2012 concluded that “Due to the limited evidence available and the risk of bias in the published results, the evidence that neutering reduces the risk of mammary neoplasia, and the evidence that age at neutering has an effect, are judged to be weak and are not a sound basis for firm recommendations.”

Schneider, R., Dorn, C.R. and Taylor, D.O.N. (1969) Factors influencing canine mammary cancer development and postsurgical survival. Journal of the National Cancer Institute, 43 (6), pp. 1249-126 https://doi.org/10.1093/jnci/43.6.1249
Beauvais, W., Cardwell, J.M. and Brodbelt, D.C. (2012) The effect of neutering on the risk of mammary tumours in dogs—a systematic review. Journal of Small Animal Practice, 53 (6), pp. 314-322 https://doi.org/10.1111/j.1748-5827.2011.01220.x
Stavisky, J. and Wareham, K. (2018) Age at neutering and mammary tumours in bitches
Egenvall, A. et al. (2005) Incidence of and survival after mammary tumors in a population of over 80,000 insured female dogs in Sweden from 1995 to 2002. Preventive Veterinary Medicine, 69 (1-2), pp. 109-127 https://doi.org/10.1016/j.prevetmed.2005.01.014
Gedon, J., Wehrend, A. and Kessler, M. (2021) Ovariectomy reduces the risk of tumour development and influences the histologic continuum in canine mammary tumours. Veterinary and Comparative Oncology. https://doi.org/10.1111/vco.12793

As well as questions about the benefit of neutering on preventing mammary tumours, questions also arise about whether ovariohysterectomy at the time of mammary tumour removal is beneficial.

Kristiansen, V.M. et al. (2013) Effect of ovariohysterectomy at the time of tumor removal in dogs with benign mammary tumors and hyperplastic lesions: a randomized controlled clinical trial. Journal of Veterinary Internal Medicine, 27 (4), pp. 935-942 https://doi.org/10.1111/jvim.12110
Kristiansen, V.M. et al. (2016) Effect of ovariohysterectomy at the time of tumor removal in dogs with mammary carcinomas: a randomized controlled trial. Journal of Veterinary Internal Medicine, 30 (1), pp. 230-241 https://doi.org/10.1111/jvim.13812
Overley, B. et al. (2005) Association between ovarihysterectomy and feline mammary carcinoma. Journal of Veterinary Internal Medicine, 19 (4), pp. 560-563 https://doi.org/10.1111/j.1939-1676.2005.tb02727.x

Pyometra Surgical ovariohysterectomy is considered the safest and most effective treatment, as the source of infection is removed, and recurrence prevented. Medical treatment can be an alternative in young and otherwise healthy breeding animals with open cervix and without other uterine or ovarian pathologies.

Turkki, O.M. et al. (2023) Postoperative complications and antibiotic use in dogs with pyometra: a retrospective review of 140 cases (2019). Acta Veterinaria Scandinavica, 65, no. 11. https://doi.org/10.1186/s13028-023-00670-5
Hagman, R. (2022) Pyometra in small animals 2.0. Veterinary Clinics of North America: Small Animal Practice, 52 (3), pp. 631-657. https://doi.org/10.1016/j.cvsm.2022.01.004
Hagman, R. (2011) A breed-matched case-control study of potential risk-factors for canine pyometra. Theriogenology, 75 (7), pp. 1251-1257 https://doi.org/10.1016/j.theriogenology.2010.11.038
Gibson, A. (2013) A retrospective study of pyometra at five RSPCA hospitals in the UK: 1728 cases from 2006 to 2011. Veterinary Record, 173 (16), p. 396 https://doi.org/10.1136/vr.101514
Hagman, R. (2018) Pyometra in small animals. Veterinary Clinics of North America: Small Animal Practice, 48 (4), pp. 639-661 https://doi.org/10.1016/j.cvsm.2018.03.001

Medical treatment of pyometra

Fieni, F., Topie, E. and Gogny, A. (2014) Medical treatment for pyometra in dogs. Reproduction in Domestic Animals, 49 (s2), pp. 28-32 https://doi.org/10.1111/rda.12302
Ros, L., Holst, B.S. and Hagman, R. (2014) A retrospective study of bitches with pyometra, medically treated with aglepristone. Theriogenology, 82 (9), pp. 1281-1286 https://doi.org/10.1016/j.theriogenology.2014.08.011

Urinary incontinence In the case of urinary incontinence there is published evidence looking, not only at the risk of urinary incontinence associated with neutering, but also at the effect of age of neutering on the risk.

Beauvais, W., Cardwell, J.M. and Brodbelt, D.C. (2012) The effect of neutering on the risk of urinary incontinence in bitches–a systematic review. Journal of Small Animal Practice, 53 (4), pp. 198-204 https://doi.org/10.1111/j.1748-5827.2011.01176.x
O’Neill, D.G. et al. (2017) Urinary incontinence in bitches under primary veterinary care in England: prevalence and risk factors. Journal of Small Animal Practice, 58 (12), pp. 685-693 https://doi.org/10.1111/jsap.12731
Pegram, C. et al. (2019) Associations between neutering and early‐onset urinary incontinence in UK bitches under primary veterinary care. Journal of Small Animal Practice, 60 (12), pp. 723-733 https://doi.org/10.1111/jsap.13072
Pegram, C. et al. (2019) Spaying and urinary incontinence in bitches under UK primary veterinary care: a case–control study. Journal of Small Animal Practice, 60 (7), pp. 395-403. https://doi.org/10.1111/jsap.13014 The December 2019 edition of inFOCUS contains a summary of this paper. https://infocus.rcvsknowledge.org/spaying-and-urinary-incontinence-in-bitches-under-uk-primary-veterinary-care-a-case-control-study/

Prostatic disease While experimental studies have demonstrated the effect of testosterone (and therefore the protective effect of castration) on the development of benign prostatic hyperplasia more recent epidemiological studies have demonstrated an increased incidence of prostatic carcinoma in castrated dogs. It may therefore be necessary to weigh the relative risks of different prostatic diseases in making recommendations for an individual dog.

Berry, S.J. (1986) Effect of age, castration, and testosterone replacement on the development and restoration of canine benign prostatic hyperplasia. The Prostate, 9 (3), pp. 295-302 https://doi.org/10.1002/pros.2990090308
Christensen, B.W. (2018) Canine prostate disease. Veterinary Clinics of North America: Small Animal Practice, 48 (4), pp. 701-719 https://doi.org/10.1016/j.cvsm.2018.02.012
Polisca, A. (2016) A retrospective study of canine prostatic diseases from 2002 to 2009 at the Alfort Veterinary College in France. Theriogenology, 85 (5), pp. 835-840 https://doi.org/10.1016/j.theriogenology.2015.10.030
Lévy, X. (2014) Diagnosis of common prostatic conditions in dogs: an update. Reproduction in Domestic Animals, 49 (s2), pp. 50-57 https://doi.org/10.1111/rda.12296
Schrank, M. and Romagnoli, S., 2020. Prostatic neoplasia in the intact and castrated dog: How dangerous is castration? Animals, 10 (1), p. 85 https://doi.org/10.3390/ani10010085
Bryan, J.N. (2007) A population study of neutering status as a risk factor for canine prostate cancer. The Prostate, 67 (11), pp. 1174 https://doi.org/10.1002/pros.20590
Sorenmo, K.U. (2003) Immunohistochemical characterization of canine prostatic carcinoma and correlation with castration status and castration time. Veterinary and Comparative Oncology, 1 (1), pp. 48-56 https://doi.org/10.1046/j.1476-5829.2003.00007.x

Other Updated 9 May 2025

Hatch, A.L. et al. (2025) Dogs neutered prior to perineal herniorrhaphy or that develop postoperative fecal incontinence are at an increased risk for perineal hernia recurrence. Journal of the American Veterinary Medical Association, 263 (4), pp. 1–6. https://doi.org/10.2460/javma.24.07.0487
Johnson, K.A. et al. (2024) Cystine urolithiasis–free duration after first occurrence and treatment is longer for castrated dogs than for sexually intact male dogs. Journal of the American Veterinary Medical Association, 262 (12). https://doi.org/10.2460/javma.24.05.0299
Low, D. (2024). Does early neutering increase the risk of cranial cruciate ligament rupture? Veterinary Evidence, 9 (2). https://doi.org/10.18849/ve.v9i2.678
Graves, J.L. et al. (2023) Body weight, gonadectomy, and other risk factors for diagnosis of osteoarthritis in companion dogs. Frontiers in Veterinary Science, 10, no. 1275964 https://doi.org/10.3389/fvets.2023.1275964
Sundburg, C.R, (2016) Gonadectomy effects on the risk of immune disorders in the dog: a retrospective study. BMC Veterinary Research, 12, 278 https://doi.org/10.1186/s12917-016-0911-5
Florey, J., Ewen, V. and Syme, H. (2017) Association between cystine urolithiasis and neuter status of dogs within the UK. Journal of Small Animal Practice, 58 (9), pp. 531-535. https://doi.org/10.1111/jsap.12707
Smith, A.N. (2014) The role of neutering in cancer development. Veterinary Clinics of North America: Small Animal Practice, 44 (5), pp. 965-975 https://doi.org/10.1016/j.cvsm.2014.06.003
Polton, G.A. (2006) Breed, gender and neutering status of British dogs with anal sac gland carcinoma. Veterinary and Comparative Oncology, 4 (3), pp. 125-131 https://doi.org/10.1111/j.1476-5829.2006.00100.x
Oberbauer, A.M., Belanger, J. and Famula, T.R. (2019) A review of the impact of neuter status on expression of inherited conditions in dogs. Frontiers in veterinary science, 6, p.397 https://doi.org/10.3389/fvets.2019.00397
Adams, P. (2011) Influence of signalment on developing cranial cruciate rupture in dogs in the UK. Journal of Small Animal Practice, 52 (7), pp. 347-352 https://doi.org/10.1111/j.1748-5827.2011.01073.x
Robinson, K.L. (2020) Neutering is associated with developing hemangiosarcoma in dogs in the Veterinary Medical Database: an age and time-period matched case-control study (1964-2003). The Canadian veterinary journal, 61 (5), pp.499-504. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7155881/
Perry, K.L., Fordham, A. and Arthurs, G.I. (2014) Effect of neutering and breed on femoral and tibial physeal closure times in male and female domestic cats. Journal of Feline Medicine and Surgery, 16 (2), pp. 149-156. https://doi.org/10.1177%2F1098612X13502977