Doing the least harm

Sara Fox Chapman MS, DVM, MRCVS, VetMFHom

Published 22 May, 2018

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This edition by USA Sara Fox Chapman considers the option of gonad sparing sterilisation and the evidence for not routinely castrating and spaying.

Gonads aren’t an afterthought

A holistic approach to population control

Routine de-sexing of dogs has been challenged following publication of studies indicating that neutering has unintended negative consequences.

The statement by the RCVS Council in November 2017 stated that all veterinary medicine must be evidence based, or be based on sound scientific principles, otherwise prosecution under the animal welfare act is threatened. The current evidence for routine neutering for health is very poor, and to perform a major operation leaving permanent disruption of the intricate hormonal interplay is unsound.

This article looks at the alternative surgical approaches to the standard ovariohysterectomy and castration employed by most vets in the UK.

It also considers studies on the effects of gonadectomy from the late 80s through the present. These studies, with breed specific studies of the Golden Retriever, Vizsla, Labrador Retriever, and German Shepherd, indicate that neutering increases the incidence of obesity, incontinence, joint problems, and neoplasia.

Recent studies extend this information, indicating that gonadectomised dogs are less adept in learning and recalling mazes, more likely to show increased aggression toward human strangers, and have an increased incidence of immune-mediated disease and intervertebral disc disease.

However sterilization is deemed important as a means of animal population control, and hysterectomy is valuable as a means of pyometra prevention. Potentially 'doing the least harm' is detailed below.

Gonad Sparing Sterilization

There are other options to gonadectomy for both male and female dogs. They are as safe and effective as the more traditional spay and neuter. Males can be vasectomised, and females can have a complete hysterectomy (including the cervix), leaving the ovaries – also called an ovary sparing spay. The AVMA now includes these among the sterilization options described to owners on the public information section of their website (AVMA).

Why sterilize dogs at all? Why not leave them intact? For males the answer is solely to prevent reproduction. Why not choose vasectomy? This surgery is somewhat delicate, as the vasa deferentia are isolated and a section of each tube is removed to ensure the male is sterile. There seems to be very little post-op discomfort, and vasectomized dogs heal more quickly than castrations.

In addition to the vasectomy option, Ark Sciences markets Zeuterin, a zinc gluconate compound that is injected into the testicles to produce irreversible fibrosis and sterility. The dog’s testosterone production drops to about 50% of normal, which may be sufficient to support normal growth and development and prevent the increased incidence of certain cancers. There are some rare, relatively mild, potential side effects, discussed in detail on the Zeuterin website(Zeuterin). Other options to vasectomy and Zeuterin that are discussed on the Parsemus Foundation website include epididymal injections of scarring agents and some experimental procedures (Parsemus).

The ovary sparing spay was pioneered by Dr. Kutzler of Oregon State. The Parsemus Foundation website has information about the procedure, including a video (Parsemus). The ovary sparing spay is not much more difficult than a traditional spay, and competent surgeons with interest in the procedure could perform it. The ovaries are left in place, and the entire uterus and cervix are removed, creating a slightly longer and lower midline incision than is the norm in the US.

Flank spays are more common in Europe, and some vets in the US perform OSS with several small flank incisions. It is essential to remove the entire cervix in this procedure. The ovaries will still be producing progesterone, which could cause hypertrophy of any bit of uterus that is left, possibly leading to an eventual pyometra. I suggest it for all non-breeding bitches, if the owner needs to have them sterilized, or is concerned about pyometra incidence.

There are some vets that perform tubal ligations. I would not recommend this sterilization option, as the uterus remains in the bitch, and the repeated cycling will result in endometrial hyperplasia and the possibility of pyometra. Tubal ligation is less invasive, but with bitches, pyometra is a serious concern.

In Sweden, most dogs are insured, and 90% of bitches are intact, so insurance data provides excellent statistics on pyometra incidence in this population. Incidence of pyometra in aged bitches (7 and over) varies greatly by breed, from 3% to 66%. The overall incidence, across breeds, by 10 years of age is 19%. Breeds with an incidence of 50% or higher are: Bernese Mountain Dog, Great Dane, Leonberger, Rottweiler, Staffordshire Bull Terrier, Keeshond, Newfoundland, Bouvier (Jitpean, et al).

It can be hard to find veterinarians who are willing to perform gonad sparing sterilisations. It may be ideal, for the animal’s health, to not sterilise animals at all. We don’t know if stopping the flow of sperm in a dog’s body, or removing the feedback effects of the uterus on the ovaries could have deleterious effects. Based on the research evidence, it appears advantageous overall for animals to retain their gonads, if they must be sterilised.

Caveats to Gonad Sparing Sterilization

There are caveats to performing these surgeries. Ensure that owners understand what they are requesting. A dog that is sterilised and retains its gonads is psychologically intact, and will have normal mating desires. These are not problematic for many individuals, especially as the lack of discharge decreases the spread of estrus pheromones, and seems to make the bitch less attractive to males. Vasectomised males will mount, tie, and ejaculate, and hysterectomised females will flag and stand for breeding.

Some males can develop inter male aggressive tendencies, and this can be severe enough that castration is the only sensible option.

Vasectomised and hysterectomised individuals will still be at risk for developing physical problems that are more common in intact individuals, such as prostatomegaly, perianal hernias, and perianal hyperplasia / tumours (males), mammary tumours (females), and gonadal cancers (both sexes).

The residual vaginal tissue could develop a cyst; a stump of any tissue can become cystic, and vaginal tissue does respond to hormones to some extent.

Vasectomised dogs reabsorb their sperm, and there may be swelling of the testes or vasa until an equilibrium develops. Many vasectomized men (60%) develop anti-sperm antibodies, so it is reasonable to expect that vasectomized dogs would do so also.

Hysterectomised bitches may develop behavioural and physical signs of pseudocyesis, at the same rate as intact bitches. Some dog sport organisations do not allow bitches in heat to compete, and this could theoretically include hysterectomised bitches, as they might be attractive to males.

General practice vets with an interest in surgery will have no difficulty in gaining proficiency in these procedures. People, especially people involved in dog sports or interested in CAM modalities, search for vets to perform these procedures as the problems associated with gonadectomy become more well known.

There is a list of vets performing the ovary sparing spay on the Parsemus site, but it only covers the North America. The Facebook group “Ovary Sparing Spay and Vasectomy” has resources for interested vets and lay people in their files section. This includes a list of vets performing hysterectomies and vasectomies in the UK, Ireland, Australia and North America. If you can perform these procedures, they would like to list your practice, as well. They have requests from all over the world for referrals to vets to perform vasectomy and ovary sparing spay / hysterectomy.

The Rationale for Gonadectomy

My thoughts about routine de-sexing of dogs have changed markedly in over 30 years as a vet. For my first 13 years of practice, I didn’t consider neutering a contentious issue. I believed that responsible people neuter and spay their dogs, and responsible vets encourage this practice.

I honestly believed that non-neutered males would be hormonal maniacs with rampant prostate problems, and intact bitches would be pursued by packs of males and afflicted by mammary tumours and pyometra. This proved not to be the case. The conventional wisdom of the time reinforced this; neutered animals were touted as better pets. Concerns about health issues or weight gain were scoffed at as being imaginary or incidental, or due to the owner’s poor feeding or management practices.

Like all veterinarians, I am concerned about pet overpopulation. According to estimates by the American Society for the Prevention of Cruelty to Animals, approximately 6.5 million dogs and cats are cared for by US animal shelters every year. Of these, 1.5 million animals are euthanased; 670,000 dogs (20% of dogs), and 860,000 cats (26% of cats), representing 1% of the total 140 million dogs and cats in the US. This is an improvement over the situation in the 70s when it was estimated that 12 to 20 million dogs and cats were euthanased annually, or roughly 25% of a population of 65 million (ASPCA).

Most vets routinely recommend sterilization of pet animals by castration or ovariohysterectomy to avoid unplanned litters. Most shelters and rescue organizations require sterilization, often before adoption. Until relatively recently, I also promoted these practices, even suggesting that all animals be gonadectomized (neutered) before puberty.

Questioning Routine Gonadectomy

I started having doubts about the wisdom of routine gonadectomy in the late 90s. So many of my neutered patients were obese, despite careful feeding practices. “Spay incontinence” was common in older spayed bitches. Several neutered canine athlete patients ruptured cruciate ligaments, including my own obedience competitor. I told myself that I was preventing unplanned litters and mammary cancer; yet I (subjectively) saw similar incidence of mammary cancer in intact or spayed bitches.

In 2001 I no longer routinely recommended routine neutering. This is a problem in the US, because all dogs acquired from rescue groups are de-sexed, often before adoption. Many shelters gonadectomise juvenile animals as young as eight to ten weeks to ensure that their new owners can not accidentally or intentionally breed them. Responsible breeders often require de-sexing of pet stock by a year of age or sooner. Many breeders are now familiar with the potential issues associated with early removal of sex hormones, so there is some movement toward later sterilization, or sterilization that does not remove the gonads.

The Evidence Linking Gonadectomy to Increased Incidence of Disease

During the next few years, I read with interest articles about the positive and negative effects of neutering. Evidence had been accumulating since the late 1980s that there were significant health implications of neutering.

I was under the mistaken impression that castrated males would be less likely to develop prostate cancer; however a 1987 study showed that castration does not decrease the incidence of prostatic carcinoma (Obradovich, et al). Gonadectomy was shown, in prospective studies, to affect final bone length (Salmeri, et al), and the collagen to muscle ratio of the urinary tract (Ponglowhapen, et al, as well as causing a deterioration in competency of urethral closure.

I had always though that neutered animals were ‘better’ pets, yet studies showed ovariohysterectomy of GSD bitches resulted in increased reactivity compared to their sexually intact cohort (Kim, et al). Castration as a treatment for behaviour problems was shown to have no effect on aggression toward strangers or fear of inanimate objects, though it did decrease roaming, urine marking, and fighting with other males.

Intact males were also less likely to develop signs of cognitive dysfunction than neutered males (Hart). This information bothered me. Like hopefully all vets, I try to ‘do no harm’ in treating animals, yet it seemed that the common practice of sterilisation may have caused more harm than benefit for some patients.

There is a treasure trove of data in Dr. Root Kustritz’s review articles, the most recent published in 2012 (Root Kustritz). Breed specific studies continue to be published; a Feb 2013 study at the University of California at Davis (UC Davis) examined the effect of neutering on joint disease and cancer incidence on Golden Retrievers.

In Feb 2014, a cohort study of Vizslas evaluated the association between neutered status and the incidence of cancer and behaviour problems (Zink, et al). The authors of the Golden Retriever study at UC Davis published a July 2014 study comparing the Golden results with similar parameters in Labradors (Hart, et al). A 2015 UK study (Parker, et al) and a 2018 US study  revealed increased incidence of IVDD in neutered Dachshunds and Pekingese.

The AVMA (American Veterinary Medical Association) has reevaluated its position on sterilisation, and gonad sparing alternatives to conventional gonadectomy (vasectomy and hysterectomy) were recently added to the AVMA website as rational sterilization options for pets. 

Kustritz’s literature reviews (Root Kustritz) compile evidence across breed lines showing definite effects of removing the gonads, aside from the obvious one of population control. Studies of the effect of gonads have proliferated in recent years, revealing significant effects on the incidence of aggression, (Farhoody, et al) immune disorders, (Sundburg, et al, Kelch) and spatial performance as measured by maze learning and recall. (Mongillo, et al 2017) Actual changes in frequency of various conditions are in the papers cited above. For brevity, let’s look at just the increase or decrease in incidence:
*Behaviour – Castration decreases roaming behaviour. In one study aggression toward strangers increases in animals neutered at a young age. In other studies, owner directed aggression and reactivity increases with gonad removal. Every prospective controlled study of aggression and gonadectomy showed either no effect of gonadectomy or an increase in aggression toward people with gonad removal.

*Cognitive dysfunction - Intact males are significantly less likely to become progressively senile than castrates.

*Spatial Learning – Intact females learned and recalled a maze better than neutered animals or intact males.


Mammary tumours (half of which are malignant cancer) decrease in incidence in spayed bitches in some studies, but not in others.

Prostatic tumours (almost always malignant cancer) increase in neutered dogs. Benign prostatic hypertrophy (enlarged prostate) is very common in intact older dogs (and men) and castration (in dogs) is curative.

Bladder cancer (often malignant) is increased in gonadectomized dogs.

Testicular cancer (which rarely metastasizes) is common in aged male dogs; castration is curative.

Hemangiosarcoma (variably malignant) and osteosarcoma (often malignant) increase in gonadectomized dogs.

*Musculoskeletal problems - Hip dysplasia, anterior cruciate ligament rupture, and intervertebral disc disease increase in gonadectomized dogs.

*Urinary incontinence increases in ovariohysterectomized female dogs.

*Pyometra occurs in roughly 25% of intact bitches over 10 years of age. Surgery is curative, but there is a risk of complications.

*Hypothyroidism increases after gonadectomy in some studies, and is unaffected in others.

*Immune-mediated disease (atopic dermatitis, autoimmune hemolytic anemia, hypoadrenocorticism, hypothyroidism, and immune-medicated thrombocytopenia) increases in incidence in gonadectomized animals, and lupus increases in neutered bitches.

*Obesity occurs in about 3% of the total USA canine population, but up to 50% of gonadectomized dogs are obese.

*Some studies show a longer lifespan for gonadectomized dogs, others for intact dogs.

The UC Davis study (Torres de la Riva, et al) evaluated the overall effects of gonadectomy, as well as how age of spaying/neutering altered the effects of gonadectomy in Golden Retrievers (GR). This study found that gonadectomised animals were more likely to have four cancers: osteosarcoma, hemagiosarcoma, lymphosarcoma, and mast cell tumours. Gonadectomised GR were also at increased risk for development of hip dysplasia and anterior cruciate ligament rupture; this was true even when obesity was taken into account.

The UC Davis study indicated that the age of gonadectomy can affect the incidence of joint problems and cancer in Golden Retrievers:

*Joint problems
Males castrated early (before one year of age) developed hip dysplasia at a younger age and more often.

Dogs of either sex gonadectomized early developed anterior cruciate ligament tears at a younger age and more often.

Intact animals had the lowest incidence of joint problems.

Lymphosarcoma was more common in males gonadectomized after one year of age. Hemangiosarcoma and mast cell tumours were diagnosed more often in females gonadectomized after one year of age, and they developed these cancers at a younger age.

Intact animals had the lowest incidence of these cancers.

The same metrics were applied to a retrospective study by three of the same authors, comparing the effect of neutering on joint disease and cancer incidence between Golden (GR) and Labrador (LR) retrievers (Hart, et al).

*Joint problems
Five percent of intact GR and LR had one or more joint diseases: hip dysplasia, elbow dysplasia, or cranial cruciate ligament tear.

In LR, gonadectomy at <6 months doubles the joint disease incidence.

In GR, gonadectomy at <6months increases joint disease incidence 4 to 5 times

Three percent of intact female GR and LR had one or more neoplasia: lymphosarcoma, hemangiosarcoma, mast cell tumor, mammary cancer.

In female LR, gonadectomy only slightly increases cancer incidence.

In female GR, gonadectomy at any age, through 8 years, increases the rate of cancer incidence by 3 – 4 times.

Gonadectomy had only a mild increase on cancer incidence in male LR and GR.

The Vizsla study evaluated the association between neutered status and the incidence of cancer and behavioural problems (Zink, et al). Dr. Zink and her colleagues found that:

*Neoplasia - Animals desexed at any age had increased incidence of mast cell cancer, lymphoma, and all other cancers.

Animals desexed at any age had increased fear of storms.

Animals desexed at or before six months of age had increased incidence of behavioural disorders including fear of noises, storms, or gunshots, separation anxiety, submissive urination, timidity, fear biting, and aggression.

The authors excluded any animals showing any signs of behavioural problems before gonadectomy from the study.

*Neoplasia and Behaviour – Desexed animals showed an earlier onset of all cancers and behavioural disorders; the younger the age of gonadectomy, the earlier the onset of the problems studied.

The increased risk of cancer may be related to the long-term effects of blood levels of luteinizing hormone (LH) over 30 times normal, following gonad removal. LH increases dramatically after gonadectomy because of the loss of feedback inhibition from the gonadal steroids. This constant stimulation causes an increases the number of LH receptors, in tissues throughout the body, increasing their effect. LH binding to cell receptors stimulates cell division and nitric oxide release. (Zwida and Kutzler)

The veterinary community as a whole has a strong belief that spaying bitches before the first estrus results in a dramatic decrease in the incidence of malignant mammary cancer, with the widely publicized statistics of 0.5% incidence if spayed before the first estrus, 8% if spayed after one cycle, and 26% incidence if de-sexed after two or more cycles. The source for this information is a 1969 retrospective study (Schneider, et al).

...high risk of bias

A 2002 systematic literature review (Beauvais, et al) evaluated the 1969 study and the 12 other English language studies that examined the relationship between gonadectomy and mammary tumour incidence. Nine studies were judged to have a high risk of bias, four others had a moderate risk of bias. Of the four with moderate risk of bias, 3 showed slight evidence of a protective effect of gonadectomy on the development of mammary tumours, 1 showed no evidence.

The systematic review found that none of the studies controlled for all important confounding variables – age, breed, and previous treatment with synthetic ovarian steroids, all significant risk factors in the development of mammary tumours. In addition, the statistical analysis of the data in these studies was not complete.

There is probably a decrease in mammary tumour (MT) incidence associated with gonadectomy, but it is presumptive to assume that an increase in mammary tumour incidence (roughly half of which are malignant) overrides all other health concerns for all bitches. Overall incidence of mammary cancer in US bitches (intact and gonadectomized) is 3.4%. (Root Kustritz)

The 1969 statistics seem to inflate the mammary tumour risk in intact bitches. As half of all mammary tumours are malignant, the 1969 study would predict an overall incidence of 52% MT in intact bitches. In Sweden, where 90% of all dogs are intact, a 2012 study found an overall 13% incidence of mammary tumours, both benign and malignant (MT). (Jitpean, et al)

If we account for the fact that 10% of these bitches are spayed, and use the figure of a 1% incidence of all MT in spayed bitches, we still arrive at a total of 14.3% incidence of all MT in intact bitches.

Those confounding variables may have been quite significant, particularly as synthetic hormones were widely used in dogs during the 1960s.

The Swedish statistics are compiled by insurance companies by breed, and reveal considerable differences in risks between breeds. Some breeds have a relatively low incidence of mammary tumours by 10 years of age, and a high incidence of other malignant cancers (Bernese Mountain Dog, 14% MT, and Golden Retriever 10% MT) and / or a high incidence of joint problems (Labrador 11% MT, Newfoundland 8% MT). (Jitpean, et al) Bear in mind that MT can be diagnosed more readily than internal cancers. The presence of gonads might help protect individuals of these breeds from developing problems of greater significance to them than MT.

Population control is a very strong reason to gonadectomise dogs, so it is unlikely that the humane societies and shelters are going to be changing their policies anytime soon! As veterinarians and dog lovers, we can see that this is not a simple choice for a beloved companion.

We certainly don’t want animals to breed indiscriminately, but we want our own dogs, and our patients, to live long healthy lives. As many breeds are prone to joint problems, cancers, and behavioural problems, it may be optimal that they retain their gonads life long for their beneficial effect on these health conditions. As we can see from the breed oriented surveys, even superficially similar breeds like Labrador and Golden Retrievers can show a large difference in the effect of gonadectomy on health.

The homeopathic perspective

It has long been recognised by homeopathic vets that gonadectomy appears to increase serious disease. Those familiar with the basics of homeopathy will find the following useful. Those who haven't studied, qualified or practiced homeopathy might find it interesting.

Homeopathic medicines can often help rebalance the vital force of the body, but gonad removal can be a significant obstacle to cure.

From 1999 to 2002, I attended courses with the Homeopathic Practitioners Teaching Group in Oxford, culminating in successful qualification as a VetMFHom. During this time we discussed the suppressive effects of removing the gonads. Our domestic animals do not naturally experience menopause, so the removal of gonads in any animals, even older animals, is suppressing a sycotic outlet. John Saxton referred to the reproductive system as the spiritual home of the sycotic miasm, and postulates that such practices as gonadectomy are likely to increase the incidence of sycotic diseases such as cancer (Saxton).

As a vet in the US, I had limited experience with intact animals, as virtually all pet dogs and cats are gonadectomised. My colleagues in countries where more animals are left intact felt that they saw more chronic disease in neutered animals.

As homeopathic vets, we understand the principle of obstacles to cure. In Aphorism 94 of The Organon, Hahnemann enjoins the practitioner to evaluate the patient’s situation to determine what factors in this patient may slow homeopathic healing (O’Reilly). Hahnemann does not specifically mention castration, as an obstacle to cure, but his patients were mostly human. In Aphorism 203, Hahnemann decries surgery that removes local symptoms without curing the internal miasmatic disease as criminal.

Castration is solely focused on preventing natural body function, and that should be problematic to the homeopathic mind.

Consider the broad physiologic functions of the gonads and gonadal hormones, as summarized by Lawless: (Lawless 2010)

  • Development of secondary sex characteristics = prevents vaginal infantilism= decreases some cancers, increases mammary cancer.
  • Estrogen role in bone and cartilage homeostasis = normal joint development, maintains bone and cartilage strength.
  • Gonadal androgens = maintain muscle mass and strength, regulate fat deposition.
    Testosterone and estrogen = neuroprotective function.
  • Sex steroids = modulate immune function by enhancing tissue self-recognition.

An understanding of the physiologic role of steroids will help us in choosing useful rubrics, as the specific castration rubrics are quite small.

Schroyens Synthesis repertory lists:
MIND, Castration, ailments after: staph
FEMALE GENITALIA /SEX, Castration, ailments after: caust, lach, staph, thuj

Obviously, these are just some of the remedies that may be helpful. This tiny rubric is certainly incomplete, though these do include some remedies which I have found useful for weakness (including bladder sphincter weakness), and post-castration behavioural problems.

In choosing rubrics, consider if the animal’s signs are greater than, or occurred earlier than, the signs often seen in de-sexed animals. It is important to understand the constellation of steroid effects, and the susceptibility of various breeds and individuals. Patients will manifest their disease in their weakest or most susceptible system. For a dachshund or corgi, that may lead to IVDD; for a boxer or Golden, cancer; for a Vizsla or Springer, anxiety.

Saxton and Gregory state, in their Textbook, that:

“some veterinary homeopaths consider that neutered animals require more prolonged courses of homeopathic medicine than those who are entire.”

It is impossible to know with certainty if a neutered animal would have responded better to treatment if it had not been neutered. I have found that some spayed females responded better to homeopathic remedies after intercurrent dosing with Ovary sarcode / Oophorinum. I have used this in several spayed females that were not responding well to their constitutional, and it improved response to subsequent doses of the constitutional. Clarke used Oophorinum in low potencies in women, for “suffering following excision of the ovaries.” (Clark)

Yin and Yan

Geoff Johnson explores the use of sarcodes (remedies made from healthy human tissues, including hormones), their characteristics and themes in his unpublished paper. (Johnson) Sarcodes share the themes of function – performing, or failing to perform.

Johnson describes Folliculinum (oestrogen) thus:

“it would seem the 'job' or 'function' is to care. The caring can be for the family, or the whole world. It is a mothering, and is the essence of woman.”

On the other hand, “the role of testosterone is to protect and provide". Here we have yin and yan – oestrogen to mother and nurture, testosterone to protect.”

This characterization of Folliculinum is reminiscent of the caring, ‘disease to please’, nature of Carcinosin, the cancer nosode, and correlates with the increased cancer incidence in some gonadectomized animals. Similarly, the increased incidence of certain aggression and fear problems in gonadectomized animals recalls the protective theme of testosterone.

Multiple considerations

We can see how there could be multiple considerations in homeopathic treatment of neutered animals:

  1. Neutered animals exhibit an increased incidence of certain chronic diseases.
  2. Neutered animals may be less responsive to well chosen homeopathic remedies.
  3. Neutered animals may benefit from treatment with sarcodes, either as a means to mitigate to some extent the effect of removal of the gonads, or as a remedy fitting the picture of the patient.


Copyright 2018, British Association of Homeopathic Veterinary Surgeons