Are you treating spay/neuter cases like any other medical choice?

By Bruce W. Christensen, DVM, MS, DACT

As veterinarians, we are trained to develop appropriate medical recommendations using an individualized, methodical approach. We consider the signalment, history, physical exam, diagnostic findings, and logistical concerns. We deduce the most likely diagnosis and present the best options to the client's family, considering first and foremost the animal's needs and the owner's circumstances.

There is not just one plan for vomiting or one treatment for paralysis. Yet why has the recommendation for dogs and cats, for the most part, been "spay/neuter as soon as possible"? Remove major endocrine organs. As soon as possible. Full stop. Signalment, history, and family circumstances … disregarded.

For decades, this recommendation has been accepted as part of responsible pet ownership and accepted in a way that is more religious than scientific, sparked by the tragic euthanasia of thousands of healthy stray dogs and cats. Veterinarians are animal welfare advocates. Euthanizing healthy animals feels antithetical to the spirit of our profession. Preventing the production of unwanted puppies and kittens through gonadectomy fit the paradigm, so it was accepted without much argument or challenge for a long time. We touted health benefits, such as eliminating the risks of testicular cancer, prostatic hyperplasia, and pyometra. Additionally, we associated the procedure with reduced mammary cancer risk, and promoted claims, such as a reduction in prostate cancer risk, or reduction in aggression.

However, published studies challenge the dogma of universal gonadectomy^1-12 and have caused some to ask if our blind, blanket spay, and neuter recommendations violate our oath to "first do no harm."

Looking at the effects

In hindsight, the warning signs were there. We have long recognized gonadectomized animals struggle with lower metabolism, less energy, and obesity, with some experiencing incontinence.¹² Pediatric gonadectomized animals show differing growth patterns compared to those allowed to go through puberty.¹³ Coat quality deteriorates.¹⁴ These adverse effects were disregarded as necessary inconveniences attached to the greater good of decreasing the surplus population.

Now, recent studies show strong correlations between removing gonads and increased risks of neoplastic, orthopedic,^1-11 immune-mediated.¹⁵ and cognitive disorders¹⁶ in some types of dogs. Studies have shown evidence that aggression and other behaviors after gonadectomy are unpredictable and could even become worse, not better.¹⁷

Acknowledging we all care about the overpopulation of stray dogs and cats, that none of us are okay with the tragic lives they live. All are disturbed by euthanizing otherwise healthy animals. Can we step back and take an unbiased look at the solution we have been promoting for decades: pediatric gonadectomy of all dogs and cats*?

Have we solved the problem with this solution? Why has this program not made a bigger dent in the surplus stray population? Despite veterinarians faithfully sterilizing stable family pets, why are shelters still full?¹² Might the problem with stray dogs not lie primarily in the homes of families taking good care of their pets?

Have we done no harm in the process? Is a reduction in treatable conditions, such as pyometra, mammary cancer, and testicular cancer by gonadectomy worth an increase in noncurable conditions (e.g. joint disorders or internal cancers)? Have we done our patients a disservice by making them obese and saying the solution to the problem we created is to give less calories and more exercise, which the now-lethargic dogs are not as eager to perform?^12,17 Is incontinence unimportant because we can just treat it with a medication for lifetime? Is a degenerated coat negligible because it is just cosmetic? Is it no big deal to turn a bouncing, fluffy, energetic, fit keeshond into a fat, nappy couch potato? Which animal did the family envision when they adopted the puppy? Which animal has the better quality of life? Which animal has the stronger, more active bond with their humans?

Finally, are intact male dogs truly more aggressive than neutered males? Or does aggression relate instead to breeding and training (or the lack thereof)? Would we have better served our clients in strengthening the human-animal bond by focusing on early training and socialization?¹⁷ What about the mammary cancer statistic that has been misinterpreted and repeated to every veterinary student and included on many current clinical websites?¹⁸ Is anyone really seeing 26 percent of intact females coming in with mammary cancer? What is the true incidence and severity of testicular and prostate disease in intact males?

Arguments are posed from both sides of the issue. Those favoring pediatric gonadectomy will argue studies demonstrating associated health risks to gonadectomy:

1. Are retrospective analyses of medical records and can therefore only report correlation, not causation; they also do not control for variables, such as diet, preventive care, genetics, and overall environment that might also affect disease status.
2. Ignore other studies that report increased longevity in gonadectomized pets.
3. Are biased because dogs with poor orthopedic conformation (and therefore predisposed to joint disorders) are more likely to be spayed/neutered instead of bred.
4. Come from referral institutions and that is why they include serious cancers and orthopedic conditions, but neglect to report diseases that general practice vets would treat, including testicular cancer, mammary cancer, and pyometra.

Those promoting delaying or eliminating gonadectomy argue that:

1. Even though retrospective studies do not control for outside variables, those variables are present for both affected and unaffected populations equally in the study; the large sample size and associated statistical predictive power validate the correlation.
2. Studies reporting increased longevity in gonadectomized pets use the desexed status as a proxy for better overall health care, since homes that "responsibly" spay and neuter are more likely to also provide preventative care and early veterinary care for any other disorders that may manifest in a pet's life.
3. Most pet dogs are adopted to families as puppies, long before any known predilection for poor conformation would be established. Choices to spay or neuter a dog because of poor orthopedic conformation are by far in the minority of cases.
4. Even ignoring the true incidence of each disorder, it would be much better for a dog to have diseases that are increased with being intact, such as testicular and mammary cancer and pyometra, because these are all more easily cured at the time of diagnosis than diseases increased with being gonadectomized, such as internal cancers and joint dysplasia, which are fatal or permanently life-altering.

Let's consider what we know based on peer-reviewed scientific literature:

• The shelter dog population consists of about 95 percent mixed-breed population.¹⁹ Spaying/neutering dogs from "responsible" households (especially purebred dogs, if you believe the statistics) is not helping decrease the surplus population of stray animals since they make up a tiny fraction of the shelter population. These dogs are not the ones filling shelters and not the ones at high risk of indiscriminate, accidental breeding. Plus, in this author's experience, if there is an accidental breeding, these clients are more likely to seek termination of the pregnancy rather than allow the puppies to be born.
• The incidence of testicular cancer in intact males may be 27 percent.²⁰ Of those, most are benign, and surgical removal of the affected testis at the time of diagnosis is curative.
• The incidence of benign prostatic hyperplasia (BPH) in intact males approaches 100 percent by eight years old, but the incidence of clinical BPH is much lower, consists of blood noted in the urine or ejaculate, and is easily and inexpensively cured by finasteride treatment.
• The incidence of prostatitis in intact males is unknown but is relatively low and is easily cured with appropriate antibiotic treatment in conjunction with finasteride.
• The incidence of prostatic neoplasia in dogs is quite low and is higher in neutered males than intact males, indicating a protective effect of staying intact with regard to this aggressive cancer.²¹
• Behavioral studies looking at aggression are difficult as they rely on subjective assessments, often by dog owners not trained in behavior. However, published studies do not show predictable improvement in aggression between neutered males compared to intact males except for dog-related aggression.¹⁷ Much more effective are neonatal socialization and early puppy training protocols.
• Cognitive degeneration accelerates faster in neutered males than intact males.¹⁶
• The 1969 paper¹⁸ regarding increasing risk for mammary cancer the longer you delay spaying has been misinterpreted as claiming 0.5 percent, eight percent, and 26 percent chance of getting mammary cancer if you spay before the first heat, before the second heat, and after the second heat, respectively. However, when one reads the original paper, those percentages were not reported as lifetime risks, but as percentages of the lifetime risk.¹⁸
  Other studies have reported actual lifetime risks to range from 0-15 percent for intact female dogs.² Using a recent 13 percent statistic,²² the actual risk of mammary cancer in a bitch spayed after its second heat is 26 percent of 13 percent, or roughly 3.3 percent. That is lower than what veterinarians have been taught and are telling clients, but it is actually much closer to the reality we actually observe in practice.
• The risk of pyometra, which varies with breed but averages 19 percent,²² is eliminated with any type of spay (hysterectomy, ovariectomy, or ovariohysterectomy).
• In some breeds, which have a higher incidence of lymphosarcoma, mast cell tumors, hemangiosarcoma, and osteosarcoma, early gonadectomy is correlated with a higher incidence of these aggressive tumors than found in intact individuals.^1-12
• In large breed dogs (>47 lbs), incidence of hip and elbow dysplasia and cruciate disease are higher in individuals spayed or neutered before full maturity.^1-12
• Male behaviors that seem to be reduced by neutering include libido, mounting, marking, roaming, and male dog-directed aggression.²³ Other types of aggression or behavioral disorders (separation anxiety, shyness, fear aggression, resource guarding, etc.) are either unaffected or may be increased by neutering.²⁴ In the end, hopefully, we can agree the decision to remove the gonads, major endocrine organs, is not benign and has some physiological consequences, which are not the same for every dog.

What's next?

So, what should we do as veterinarians? We should treat the decision whether (and when) to gonadectomize just like we do every other medical recommendation: it should be individualized for the pet and the family.

If you have a family who owns only one male dog and no intact female dogs, one could argue against ever neutering the dog unless it happened to develop testicular cancer. This may be especially true if the family enjoys an active lifestyle with the dog and does not want him to slow down and gain weight.

If a family owns a female dog of a breed predisposed to internal cancers and does not have an intact male dog around, then a discussion around ovary-sparing spays may be appropriate, especially if they also do not want her to slow down and gain weight.

The bottom line is we recognize the answer is not the same for every dog, for every family. We owe it to our patients and our clients to recognize this reality and treat it with the expertise and respect that we treat all other medical situations.

*Little to no work has been done in cats, and currently, we do not have evidence to warrant changing recommendations to spay or neuter early. Cats are also more likely to roam than dogs. Undoubtedly, there are also consequences of gonadectomy in cats, but information is lacking.

Bruce W. Christensen, DVM, MS, DACT, graduated from the Cornell University College of Veterinary Medicine in 2002. He completed a theriogenology residency and a master degree in reproductive physiology at the University of Florida in 2007. Dr. Christensen has worked in a private practice in Australia and has been a university professor in the theriogenology departments at both the Iowa State University and the University of California (UC), Davis. Christensen currently runs his own private practice in California, Kokopelli Veterinary Center, where he provides theriogenology services for dogs and horses. He serves on the Association of Zoos and Aquariums' Reproduction Management Center board and as a reproduction advisor to the Mexican Gray Wolf Species Survival Plan. He is a diplomate of the American College of Theriogenologists, the author of numerous journal articles and book chapters.

References

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