Hemangiosarcoma Awareness

The Spay-Neuter Impact on Hemangiosarcoma

For most of us, "should I spay or neuter my dog" is a question we get asked once, by a vet, when our dog is a few months old. We say yes the way we say yes to most things our vet recommends. We trust them. We want to be responsible. And then it is done. What we have learned since losing our Lyla to hemangiosarcoma is that this conversation is much fuller than most of us have ever had. The decision to spay or neuter your dog, when, and how, is not a single choice. It is a small set of choices, and each one affects the dog you will share your life with for the next decade and more. This article walks through those choices, gently and honestly, in the spirit of the conversation that started us thinking about them.

This page is educational and does not replace veterinary care. If your dog is showing sudden collapse, pale gums, or acute weakness, please treat it as an emergency and contact a veterinarian right away.

Table of Contents

  1. A Note Before You Begin
  2. What the Words Actually Mean
  3. The Bigger Truth: Hormones Do Far More Than Make Puppies
  4. For Male Dogs: The Four Options
  5. Cryptorchidism: One Specific Situation
  6. For Female Dogs: The Four Options
  7. Why Golden Retrievers Specifically
  8. The Mammary Cancer Study, Carefully
  9. Hormone Replacement Options
  10. Finding a Vet Who Offers These Options
  11. A Few Words to Close
  12. Sources and Further Reading

A Note Before You Begin

This article is not veterinary advice. It is a careful, honest summary of a conversation we encountered between a golden retriever breeder, Nicholberry Goldens, and Dr. Christensen, a board-certified theriogenologist (a veterinarian who specializes in reproductive medicine). Dr. Christensen graduated from Cornell in 2002, specialized in theriogenology at the University of Florida, taught at Iowa State and UC Davis, and now runs Cocopelli Veterinary Center in the Sacramento area. He has spent his career thinking carefully about reproductive surgery options for dogs.

We share this in the spirit Dr. Christensen himself shares it: gently, factually, and with no judgment for whatever choice you have already made for the dog you love. The point is the next conversation, not the last one. If you are reading this after losing a dog, please know that nothing here is meant to suggest that any choice you made was wrong. The conversation about spaying and neutering has changed in recent years, and many of us, including many veterinarians, were taught a version of it that left out a great deal. What follows is what is being learned now, offered with the same care we offer everything on this site.

What the Words Actually Mean

A few definitions, because the terminology matters more than it sounds.

Spay is the general term for making a female dog infertile through surgery. The traditional spay in the United States removes both ovaries and the uterus. But "spay" can also describe other procedures, such as removing only the ovaries, or only the uterus.

Neuter is the general term for the same in a male dog. The traditional neuter, sometimes called castration, removes both testicles. Other procedures exist that achieve infertility without removing the testicles, such as a vasectomy.

The reason this matters: when a vet says "we should spay your dog," what most people hear, and what most vets in the United States do, is the traditional version. But there are other options, and many of them preserve hormones the dog will need for the rest of its life.

The Bigger Truth: Hormones Do Far More Than Make Puppies

This is the piece that often goes unsaid. The testicles and ovaries are not simply gamete factories that exist to produce sperm and eggs. They are endocrine glands that produce hormones, testosterone in males and estrogen and progesterone in females, which support far more than reproduction. They support:

  • Bone and muscle development, especially during growth
  • Cognitive function, including the rate of mental decline as a dog ages
  • Metabolic efficiency, including how the body handles fat and uses energy
  • Behavior, including confidence, drive, and certain kinds of aggression
  • And, increasingly recognized, certain anti-cancer protections

When traditional spay or neuter removes the source of those hormones, the dog loses access to all of those non-reproductive functions, not just the reproductive ones. This is true for both sexes. While many dogs adapt to this loss without obvious problems, research is making clearer that the loss is real, and that for some breeds, including the breed most central to this site, the long-term consequences can be serious. That is the lens through which Dr. Christensen, and a growing number of veterinarians, approach this conversation. Not "should we spay or neuter," but "what is the best way to give this dog a long, healthy life, and what role does its hormonal system play in that."

For Male Dogs: The Four Options

Dr. Christensen frames the choices in four buckets. Let us walk through each.

Leave the Dog Intact

The first option, often skipped past, is to do nothing surgical. For a male dog kept under reasonable control, with no intact females in the household or close social circle, Dr. Christensen does not see a compelling health reason to neuter at all.

The two things people worry about with intact males are an enlarged prostate, which is common in older intact dogs, and aggression. The enlarged prostate is real but usually benign and rarely symptomatic. When it does cause symptoms, often a little blood in the urine in an older dog, it is treatable with finasteride, the same inexpensive medication men take for the same problem. The drug shrinks the prostate without affecting testosterone, has minimal side effects, and works reliably.

Prostate cancer is the other concern people hear about, and on this point, the science actually runs the other way. Studies show prostate cancer is more common in neutered dogs than intact ones, not less. Both rates are low, but the risk is higher after castration. If your vet has told you that neutering protects against prostate cancer, that recommendation is not supported by current evidence.

Vasectomy

A vasectomy removes a section of the vas deferens (the tube that carries sperm from the testicles) so the dog cannot impregnate a female, but it leaves the testicles, and the testosterone, intact. The dog is functionally infertile but still has full access to its own hormonal system.

Because a vasectomy does not touch the testicles, it can be performed at any age, including before full growth. It is genuinely the best of both worlds for many male dog owners: prevention of unwanted breeding without the metabolic, cognitive, behavioral, or oncologic consequences of removing the testicles. The catch is finding a vet who does vasectomies. Most general practice vets do not, and you may need to find a reproductive specialist.

Traditional Neuter (Castration)

The traditional neuter removes both testicles, eliminating the source of testosterone in the dog's body. This is the procedure most people in the United States have done for their male dogs, often before the dog is a year old.

The reproductive effect is straightforward: the dog cannot produce sperm and is permanently infertile. The non-reproductive effects, as Dr. Christensen lays them out:

  • On growth. Testosterone helps regulate when bones stop growing. Without it, the bones grow longer than they otherwise would, which is associated with a higher risk of orthopedic problems later in life such as hip dysplasia, elbow dysplasia, and cruciate ligament rupture. This is especially significant for large breeds.
  • On muscle and metabolism. Testosterone supports muscle building and the efficient metabolism of nutrients. Without it, dogs tend to gain weight more easily and have less energy and drive. Many working-dog handlers have known this for years and choose not to neuter their working dogs.
  • On cognition. Studies suggest neutered dogs experience faster cognitive decline as they age than intact dogs.
  • On behavior. Testosterone influences drive, confidence, libido, and intramale aggression. Intramale aggression does tend to decrease after neutering. Other behavioral changes are more variable.
  • On cancer risk. This is where the picture gets more complex, and we return to it later in this article.

If you do decide to neuter, the timing matters. Dr. Christensen recommends waiting until the dog has reached full growth. For large breeds like golden retrievers, that means a minimum of 18 months, sometimes longer. Before that, you are interrupting growth processes that you cannot recover.

The Suprelorin Implant

Suprelorin, sometimes spelled Superlorin (generic name deslorelin), is a small hormonal implant placed under the skin that suppresses the entire reproductive cascade. In simplified terms, it tells the brain to stop telling the testicles to produce testosterone. Within a few weeks the dog is functionally infertile, with testosterone levels near zero, while still anatomically intact.

The major advantage is that it is reversible. After 6 to 12 months, depending on the formulation, the implant wears off and the dog returns to normal hormone production. For situations where a temporary infertility is what is wanted, this is a useful tool. In the United States, Suprelorin's official label is for ferrets, but vets can use it in dogs through an import process. In Canada and other countries, it is officially labeled for dogs. There is also a small set of options involving chemical castration via injection. Dr. Christensen mentions these but notes they have fallen out of favor because of complication rates.

Cryptorchidism: One Specific Situation

Cryptorchidism is when one or both testicles never descend into the scrotum and stay in the abdomen. It is a specific situation worth addressing because it changes the calculus.

A retained testicle does carry an elevated risk of testicular cancer. But two important points temper this. First, testicular cancer in dogs is almost always benign. It rarely spreads. The most extreme case Dr. Christensen has seen reported was a cancer that spread from one testicle to the other, and even that is rare. If a dog with both testicles in the scrotum gets testicular cancer, the owner usually notices the testicle growing, and the cancer is found early and is cured with removal.

Second, the problem with a retained testicle is that you cannot see it grow. So if cancer develops inside the abdomen, it can get quite large before anyone notices. The recommendation, then, is to remove the retained testicle, or both if the procedure is now happening, once the dog has reached full growth. The same principle applies: wait for the orthopedic and metabolic growth to complete, then do the surgery.

For Female Dogs: The Four Options

For female dogs, the bucket structure is similar.

Leave the Dog Intact

Here, the picture is different than for males. Intact female dogs face a meaningful risk of pyometra, a uterine infection that can be life-threatening. The incidence of pyometra in intact females is between 25 and 50 percent over a lifetime, depending on the breed and the study. Half of intact female dogs may experience this serious infection at some point.

Pyometra can present as an "open" infection, with visible discharge, or a "closed" one, with no discharge but the dog gets sicker as toxins accumulate. It generally requires emergency surgery. For this reason, Dr. Christensen believes that leaving a non-breeding female completely intact for her whole life is not the best choice. Some other countries, in Scandinavia for example, have made elective spay surgeries illegal and accept the pyometra rate that comes with that. Dr. Christensen, and many American vets, find that trade-off too steep. So for female dogs not intended for breeding, some surgical option is usually wise. The question is which one.

Traditional Spay

The traditional spay removes both ovaries and most of the uterus. The dog cannot get pregnant, cannot get pyometra assuming the surgery was complete, and loses access to her ovarian hormones. The hormone loss has the same kinds of consequences described for males: effects on growth, metabolism, behavior, cognition, and certain cancer risks. For large breeds, those consequences appear to be more significant.

Ovary-Sparing Spay (OSS, or Hysterectomy)

This procedure removes the entire uterus, leaving the ovaries. The dog cannot get pregnant. She cannot get pyometra. But she retains her ovaries and therefore her hormonal system. She will continue to cycle internally, though without visible bleeding, since the source of the blood, the uterus, is gone.

For dogs that benefit from continued hormone exposure, which increasingly appears to include large breeds and especially golden retrievers, OSS is a strong option. The dog gets the protection from pregnancy and pyometra, while keeping the metabolic, cognitive, and oncologic benefits of her ovaries. A few important considerations specific to OSS:

  • The whole uterus must come out, including the cervix. If a vet leaves a stump of uterus, that stump can still get infected, a condition called stump pyometra. This is a surgical technique issue, and it is why you want a vet experienced with OSS specifically.
  • The dog will still show heat behaviors roughly twice a year, even though she will not bleed. Her vulva will swell, her pheromones will change, and she will be attractive to intact males. If she has an OSS and breeds with an intact or vasectomized male, there is a real risk of serious complications because the semen has nowhere to go. The scar tissue at the end of the vagina can fail, releasing semen into the abdomen and causing a surgical emergency. So OSS dogs need to be kept reliably away from intact males during her heat periods. For most owners, who do not have intact males in their daily life, this is not difficult. For owners with multiple dogs, it requires planning.
  • OSS should wait until after the first heat cycle. The reasoning is the same as for delaying neutering in males: you want the dog to have completed growth, both skeletal and reproductive, before any surgery. There is also a specific issue called recessed vulva, sometimes called hooded vulva, where the external anatomy stays in a juvenile configuration if the dog is spayed too early, leading to chronic urinary tract infections later in life. Letting the female go through one full heat cycle before OSS allows her external anatomy to mature.

Ovariectomy

This is the opposite of OSS: remove the ovaries, leave the uterus. Once the ovaries are gone, the uterus becomes inactive (no more hormonal signals reach it). It will not get infected, and it will not get cancer. The dog will not cycle, and the breeding-risk concerns of OSS do not apply.

The downside is the same as a traditional spay: the dog loses her ovarian hormones and the protections they provide. The advantage over traditional spay is that less tissue is removed, often with a smaller incision and a faster recovery, and ovariectomy can be performed laparoscopically, which means even smaller incisions, less bleeding, and a quicker recovery. If you have decided that removing the ovaries is the right choice for your specific dog, ovariectomy is generally preferable to a traditional spay. Both achieve the same hormonal endpoint with less surgical intervention.

Why Golden Retrievers Specifically

Goldens are one of the breeds for which all of this matters most. They are unfortunately predisposed to several serious, aggressive cancers, including:

  • Hemangiosarcoma, the cancer of blood vessel linings that this site exists to raise awareness of
  • Lymphoma, a cancer of the lymphatic system
  • Mast cell tumors, a cancer of certain immune cells
  • Osteosarcoma, bone cancer (more often associated with even larger breeds)

These are aggressive cancers, often internal, often not noticed until they have advanced. They are part of what makes golden ownership both joyful and, for many of us, eventually painful. Cancer does not happen because of a single thing going wrong. It is the result of multiple checks and balances in the body failing in the same set of cells. Golden retrievers, as a breed, are born with some genetic mutations that already weaken one or two of those checks. They are starting closer to the line than dogs from many other breeds.

Separately, the choice to remove the gonads at an early age appears to push some of those dogs further toward the line. The widely cited University of California, Davis study of 759 Golden Retrievers, often associated with Dr. Benjamin Hart and colleagues, has shown a clear correlation between early traditional spay or neuter and increased risk of certain cancers, including hemangiosarcoma, in goldens. The leading scientific explanation for why, the LH theory, is the subject of our companion article.

This is also where the story about mammary cancer gets corrected.

The Mammary Cancer Study, Carefully

For decades, vets have told dog owners that spaying a female dog before her first heat dramatically reduces her risk of mammary cancer. This claim comes from a study published in the 1960s. The numbers are often quoted: 0.5 percent risk if spayed before the first heat, 8 percent if spayed after the first heat, 26 percent if spayed after the third heat.

The problem is those numbers have been misread by generations of veterinary students. The original paper did not say those were lifetime risks. It said those were the percentages of an intact female's lifetime risk. So the 26 percent figure, for example, means 26 percent of whatever an intact female's lifetime mammary cancer risk is.

What is that intact lifetime risk? It is hard to say precisely, but Dr. Christensen estimates it generously at perhaps 10 percent. So a female spayed after her third heat is not at 26 percent lifetime risk; she is at 26 percent of 10 percent, which is roughly 2.6 percent. A female spayed after her first heat is at about 0.5 percent.

The difference between "26 percent lifetime risk if you wait" and "2.6 percent lifetime risk if you wait" is enormous, and it changes the calculation. Mammary tumors, when they occur, are about half benign and are usually findable by feeling the dog's belly during regular petting. They are also straightforward to remove. By contrast, hemangiosarcoma is internal, often silent, aggressive, and rarely curable. Dr. Christensen's plain conclusion is this: if you are weighing a slightly higher risk of mammary cancer, caught early and often benign, against a higher risk of hemangiosarcoma, often missed until emergency and often fatal, you would take the mammary cancer risk every time.

Hormone Replacement Options

For dogs already spayed or neutered traditionally, are there options to restore some of what was lost? Yes, with limitations.

For males, testosterone replacement is possible, and Dr. Christensen and others have used it in cases of dogs neutered very young whose owners later wanted to support their long-term health. It is not standard care, but it is an option.

For females, replacing estrogen and progesterone reliably is harder, and it is not a routine option. But there is a different approach. If the leading theory is that elevated luteinizing hormone (LH) after gonadectomy is what drives a number of long-term problems, including increased cancer risk, then lowering LH might help. The same Suprelorin implant that suppresses testosterone in intact males works on the pituitary in females and shuts down LH production. For a spayed female with no ovaries, there is no risk of ovarian cysts (the main concern with Suprelorin in intact females), and the implant simply turns off the elevated LH.

This is a topic still being actively studied, largely by Dr. Michelle Kutzler's lab at Oregon State University. It is not yet a routine recommendation, because the underlying causation has not been proven. But for an owner concerned about long-term risk in an already-spayed dog, it is an option worth discussing with a knowledgeable vet. For a full account of the science behind this approach, see our companion article on the LH theory.

Finding a Vet Who Offers These Options

The single biggest practical barrier most dog owners face, after all this information, is finding a veterinarian who actually does OSS, vasectomy, or the Suprelorin implant. Most general-practice vets do not. Reproductive specialists usually do.

Two resources can help. The Society for Theriogenology and the American College of Theriogenologists both maintain searchable directories of member veterinarians. Their websites let you search by state and species, so you can find a canine reproductive specialist near you. Veterinarians who are diplomates of the American College of Theriogenologists have completed specialty board certification in reproductive medicine, and they are much more likely than general practice vets to be familiar with the options described in this article.

Dr. Christensen himself sees patients at Cocopelli Veterinary Center in the Sacramento area, and people drive considerable distances to see him because OSS specialists are scarce. He also offers phone consultations for owners outside his area.

A Few Words to Close

We did not write this to second-guess any choice you have made for your dog. Whatever you chose, you chose with the information you had and the love you have, and that is what good dog people do. None of this changes that.

We are writing it because the conversation has gotten richer in the last decade, and many dog owners, and even many vets, have not caught up to it. The conversation now includes options that did not used to be on the table, science that did not used to be known, and considerations that go far beyond "should we make sure she cannot have puppies." We share it in the hope that the next time you face this decision for a dog you love, you have all of it.

For a deeper look at the science behind why these choices matter at the level of cancer risk, please see our companion article on the LH theory, which goes into the published research on what happens when the gonads are removed and the hormone that may be driving so much of what we lose with them.

Sources and Further Reading

The following sources informed this article and are good next steps for readers who want to go deeper into the science behind these decisions.

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