Clara S.S. Goh, BVSc, MS, DACVS (Small Animal), ACVS Founding Fellow (Surgical Oncology), Colorado State University
Clara S.S. Goh, BVSc, MS, DACVS (Small Animal), ACVS Founding Fellow (Surgical Oncology), is a faculty orthopedic surgeon at Colorado State University. Her research interests include stem-cell therapy and sports medicine and rehabilitation. She completed an internship, surgery residency, and surgical oncology training at Colorado State University. Dr. Goh presents and instructs numerous seminars and laboratories throughout the United States on soft-tissue, oncologic, and orthopedic surgery.
Following is a discussion of the benefits and potential adverse events of gonadectomy in large- and giant-breed dogs (Table 1). Of note, much of the literature on this topic is retrospective and based on smaller select populations, so relative risk is difficult to determine for individual animals.
|Condition||Effect of OHE on Relative Risk||Effect of Castration on Relative Risk|
|Overall longevity||Mild increase in longevity||Mild increase in longevity|
|Obesity||Moderate increase||Moderate increase|
|Cranial cruciate ligament disease||Moderate increase*||Moderate increase*|
|Hip dysplasia||Mild increase*||Mild increase*|
|Mammary tumors||Marked decrease*||N/A|
|Uterine, ovarian, vaginal tumors||Prevents||N/A|
|Perianal gland tumors||N/A||Marked decrease|
|Prostatic carcinoma||N/A||Mild increase|
|Lymphoma||Mild increase||Mild increase*|
|Mast cell tumors||Mild increase||N/A|
|Hemangiosarcoma||Mild increase*||Mild increase|
|Osteosarcoma||Mild increase*||Mild increase*|
|Transitional cell carcinoma||Mild increase||Mild increase|
|Urinary sphincter mechanism incompetence||Moderate increase*||N/A|
|Benign prostatic hyperplasia||N/A||Marked decrease|
|Perineal hernia||N/A||Moderate decrease|
*Age at time of surgery may be important.
Ovariohysterectomy (OHE) prevents pyometra but may increase risk for urinary sphincter mechanism incompetence (USMI). In general, large dogs (>15 kg) have a significantly greater risk for developing USMI than smaller dogs.4,5
Although dogs that have OHE before 3 months of age show an increased risk for USMI as compared with dogs that have OHE between 3 and 12 months of age,6 other data and analyses have not supported a causal link between age at time of OHE and risk for USMI.4,5,7,8
Prepubescent OHE can result in a recessed or hypoplastic vulva in some dogs and may predispose these animals to perivulvar dermatitis and cystitis, particularly if they are overweight and have USMI. These findings may explain the greater reported incidence of cystitis in dogs undergoing OHE before 5.5 months of age.6
Benign prostatic hyperplasia is seen in 50% of intact males by 5 years of age.9 Castration prevents benign prostatic hyperplasia as well as other associated diseases (eg, prostatitis, prostatic cysts, perineal herniation).10-12
Removing hormonal influence on the developing skeleton via gonadectomy can result in delayed physeal closure13,14 and longer-limbed conformation (Figure 1). The latter may play a role in the development of orthopedic disease, as shown in Labrador and golden retrievers neutered <6 months of age. These dogs had a 2× to 5× increased incidence of ≥1 joint disorders as compared with intact dogs.15,16
FIGURE 1 Body conformation. Both golden retrievers are adult males of similar age. The dog on the left is intact, and the dog on the right was neutered at 5 months of age. Resultant delayed physeal closure can lead to a longer-limbed conformation.
Large-breed dogs that underwent gonadectomy at <6 months of age have shown a 3× increased risk for excessive tibial plateau angle and predisposition for earlier canine cranial cruciate ligament (CCL) injury.17 Dogs that underwent gonadectomy at a nonspecified age had a 2× to 3× incidence of CCL disease as compared with intact dogs.18,19 In a study of 750 golden retrievers, none of the intact dogs had CCL disease, compared with an incidence of 5% in castrated dogs and 7.7% in spayed dogs that underwent gonadectomy at <12 months of age.16 BCS was the same for dogs with and without CCL disease. This suggests that change in conformation—not just increased body weight associated with gonadectomy—was responsible.16
Hip dysplasia may be influenced by patient sex and breed and timing of gonadectomy. In the golden retriever study,16 incidence of hip dysplasia in males neutered at <12 months of age was double that of intact males, with an earlier onset of disease. The BCS of the males with and without hip dysplasia and neutered at <12 months of age was not far greater. No significant difference in hip dysplasia incidence was seen in the females.16 Spayed or neutered boxers with a mean age of 3 years at the time of gonadectomy had a 1.5× increased risk for developing hip dysplasia.20 Data collected from the Veterinary Medical Database between 1964 and 2003 showed that gonadectomy (at a nonspecified age) increased the likelihood of hip dysplasia by 17%.18 Incidence of hip dysplasia was 6.7% in dogs that underwent gonadectomy before 5.5 months of age and 4.7% in dogs that underwent gonadectomy between 5.5 months and 1 year of age.6
Obesity plays a significant role in the development and progression of many orthopedic diseases and osteoarthritis.21 Although gonadectomy is a significant risk factor for obesity,6,22,23 gonadectomy alone is most likely less important than other environmental factors (eg, diet, exercise regimen).24
Many veterinarians are aware of the effect and timing of spaying on incidence of mammary tumors (Table 2) based on Schneider, Dorn, and Taylor’s 1969 study.25
|Reproductive Status at Time of OHE||Mammary Tumor Risk|
|Never in estrus||0.5%|
|In estrus 1 time only||8%|
In estrus ≥2 times , regardless of age
and ≤2.5 years of age
and >2.5 years of age
Spaying after the third estrous cycle and after 2.5 years of age appears to provide minimal protection against mammary tumor development.25,26 A 2010 systematic review of this and other studies on the protective effect of OHE concluded that the evidence is weak because of confounding factors and bias.27 Incidence of mammary tumors in intact females, however, increases with age and exposure to sex hormones, with increasing tumor risk between 7 and 13 years of age.28-30
Gonadectomy eliminates the potential for developing uterine, ovarian, and testicular tumors through removal of the primary organ.31 Perianal gland tumors in male dogs are treated successfully via castration.32 OHE is protective against vaginal leiomyomas and can decrease recurrence, even with incomplete surgical resection.33,34 Neutered male dogs had 2× to 8× the incidence of prostatic carcinoma as compared with intact male dogs34,35; however, the overall prevalence of prostatic cancer is <1%.35-37
A large population study showed that intact female dogs had a significantly lower risk for developing lymphoma as compared with dogs that underwent gonadectomy (at a nonspecific age) or intact male dogs.38 This finding was consistent in studies of golden retrievers and vizslas, although castration at <12 months of age was also found to be a risk factor.16,39
Gonadectomy has been associated with 2× to 4× the risk for mast cell tumors, particularly in female dogs that underwent OHE after 1 year of age.16,39,40 However, estrogen receptors have not been identified in mast cell tumors, so a direct hormonal link has not been established.41
Golden retrievers that underwent OHE after 1 year of age had 4× the incidence of hemangiosarcoma as compared with intact females or females that underwent OHE before 1 year of age.16 No significant differences in incidence of hemangiosarcoma were found in male golden retrievers.16 Similar findings were noted in a study of vizslas, although dogs that underwent OHE before 1 year of age or castration after 1 year of age also had increased risk.39 Other nonbreed-specific studies have shown similar findings for splenic and cardiac hemangiosarcoma.42,43
An increased risk for osteosarcoma was seen in rottweilers that underwent OHE or castration before 1 year of age, although the overall 13% incidence of bone sarcoma in this study group seems disproportionately high.44 Historic studies have reported a 1.3× to 1.9× increased risk for osteosarcoma in animals that underwent gonadectomy at a nonspecified age.45,46
Female dogs are more predisposed to bladder transitional cell carcinoma than are male dogs, and gonadectomy (at a nonspecified age) increases the risk up to 3× in both male and female dogs.47,48 An 8× increase in prostatic transitional cell carcinoma has also been reported in male dogs that underwent castration at a nonspecified age.36
Existing studies on the benefits and detriments of performing gonadectomy in large- and giant-breed dogs <12 months of age provide conflicting data, and most literature is retrospective. In addition, because pet longevity is increased with gonadectomy,31,49 the risk for developing cancer may be higher. On their completion, comprehensive prospective studies such as the Lifetime Golden Retriever study50 could provide clearer guidelines on when to perform OHE and castration.
For large- and giant-breed dogs, this author generally recommends OHE between the first and second estrous cycles in female dogs and castration after musculoskeletal maturity in male dogs. Although timing of gonadectomy may play a role in the development of certain diseases, patient genetics and environmental factors are likely to be equally, if not more, important.
BCS = body condition score, CCL = cranial cruciate ligament, OHE = ovariohysterectomy, USMI = urinary sphincter mechanism incompetence
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Forsee KM, Davis GJ, Mouat EE, Salmeri KR, Bastian RP. Evaluation of the prevalence of urinary incontinence in spayed female dogs: 566 cases (2003-2008). JAVMA. 2013;242(7):959-962.
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Berry SJ, Strandberg JD, Saunders WJ, Coffey DS. Development of canine benign prostatic hyperplasia with age. Prostate. 1986;9(4):363-373.
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Mann FA, Nonneman DJ, Pope ER, Boothe HW, Welshons WV, Ganjam VK. Androgen receptors in the pelvic diaphragm muscles of dogs with and without perineal hernia. Am J Vet Res. 1995;56(1):134-139.
Snell WL, Orsher RJ, Larenza-Menzies MP, Popovitch CA. Comparison of caudal and pre-scrotal castration for management of perineal hernia in dogs between 2004 and 2014. N Z Vet J. 2015;63(5):272-275.
Root MV, Johnston SD, Olson PN. The effect of prepuberal and postpuberal gonadectomy on radial physeal closure in male and female domestic cats. Veterinary Radiology & Ultrasound. 1997;38(1):42-47.
Salmeri KR, Bloomberg MS, Scruggs SL, Shille V. Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. JAVMA. 1991;198(7):1193-1203.
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Torres de la Riva G, Hart BL, Farver TB, et al. Neutering dogs: effects on joint disorders and cancers in golden retrievers. PLoS One. 2013;8(2):e55937.
Duerr FM, Duncan CG, Savicky RS, Park RD, Egger EL, Palmer RH. Risk factors for excessive tibial plateau angle in large-breed dogs with cranial cruciate ligament disease. JAVMA. 2007;231(11):1688-1691.
Witsberger TH, Villamil JA, Schultz LG, Hahn AW, Cook JL. Prevalence of and risk factors for hip dysplasia and cranial cruciate ligament deficiency in dogs. JAVMA. 2008;232(12):1818-1824.
Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM. Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clin Orthop Relat Res. 2004;(429):301-305.
van Hagen MA, Ducro BJ, van den Broek J, Know BW. Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of boxers. Am J Vet Res. 2005;66(2):307-312.
Frye CW, Shmalberg JW, Wakshlag JJ. Obesity, exercise and orthopedic disease. Vet Clin North Am Small Anim Pract. 2016; doi: 10.1016/j.cvsm.2016.04.006.
Lefebvre SL, Yang M, Wang M, Elliott DA, Buff PR, Lund EM. Effect of age at gonadectomy on the probability of dogs becoming overweight. JAVMA. 2013;243(2):236-243.
McGreevy PD, Thomson PC, Pride C, Fawcett A, Grassi T, Jones B. Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Vet Rec. 2005;156(22):695-702.
Courcier EA, Thomson RM, Mellor DJ, Yam PS. An epidemiological study of environmental factors associated with canine obesity. J Small Anim Pract. 2010;51(7):362-367.
Schneider R, Dorn CR, Taylor DO. Factors influencing canine mammary cancer development and postsurgical survival. J Natl Cancer Inst. 1969;43(6):1249-1261.
Sonnenschein EG, Glickman LT, Goldschmidt MH, McKee LJ. Body conformation, diet, and risk of breast cancer in pet dogs:a case-control study. Am J Epidemiol. 1991;133(7):694-703.
Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs: a systematic review. J Small Anim Pract. 2012;53(6):314-322.
Egenvall A, Bonnett BN, Ohagen P, Olson P, Hedhammar A, von Euler H. Incidence of and survival after mammary tumors in a population of over 80 000 insured female dogs in Sweden from 1995 to 2002. Prev Vet Med. 2005;69(1-2):109-127.
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Benjamin SA, Lee AC, Saunders WJ. Classification and behavior of canine mammary epithelial neoplasms based on life-span observations in beagles. Vet Pathol. 1999;36(5):423-436.
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Zink MC, Farhoody P, Elser SE, et al. Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. JAVMA. 2014;244(3):309-319.
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