#desex

I don’t at all mind discussing the topic when everyone remains civil about it. It’s very interesting and an aspect of veterinary medicine that’s bound to change as we gather more information. I’m happy to discuss it as long as all participants refrain from making personal insults.

It’s a long discussion folks. I’d grab a cuppa tea if that’s your thing. Also, unfortunately I can’t hide it under a ‘read more’ because it’s an answer to an ask, and Tumblr will eat the hidden part if I do. I will try to make it look pretty if you’re not interested.

Traditionally in dogs we have performed desexing (spey) by performing an ovariohysterrectomy, removing both ovaries and the uterus. Some alternatives have been suggested including tubal ligation, hysterectomy (removing only the uterus), ovariectomy (removing only the ovaries) or doing nothing. This is good. Science as a process should periodically review data, question the knowledge base and make recommendations based on new research. Otherwise it’s just dogma.

I don’t think you can claim that it is ‘clear’ that leaving the ovaries benefits the health of breeds like the GSD. The practice is still controversial at best, with some veterinarians outright labeling it at malpractice. There is some breed variability in terms of what relative benefits and risks might be expected, but I really wouldn’t call it ‘clear’.

Before I talk about various cancer risks, let’s talk about relative risks of non-cancerous conditions.

With an ovariohysterectomy (traditional spey)that is properly performed, there is zero risk of pyometra. Stump pyo can occur if remnants of the uterus or ovaries are left behind. Cruciate tears are affected by multiple factors, but desexed dogs seem more prone to them than entire dogs. Weight gain and obesity is more common in desexed dogs.

The relative risk of pyometra in non-desexed dogs is about 25%. Risks typically increase with age.

With an ovary sparing spey (hysterectomy), only the uterus is removed. Pregnancy is prevented. Pyometra can still occur if any uterine or cervix tissue remains (a stump pyo). With the apparent influence of oestrogen, these dogs may be less at risk of cruciate disease and are less at risk of obesity.

With an ovariectomy, only the ovaries are removed. This renders the dog infertile and removes the influence of oestrogen. The uterus will atrophy and shrink down without stimulation from female hormones, rendering the risk of pyometra basically zero. It may still increase the risk of obesity and cruciate disease like the traditional spey.

Considering that pyometra is often lethal, while cruciate disease is painful but treatable, personally I would err on the side of preventing pyometra. Also keep in mind that obesity in dogs can be moderated with owner control of the diet, and obesity will predispose to cruciate injury. I would recommend removing at least the ovaries.

Male dogs have less surgical options. Vasectomy can be considered, but these dogs are basically entire but infertile.

An entire male dog is more at risk of perineal hernia, benign prostatic hyperplasia, perianal adenoma and inter-male aggression. A castrated male dog is relatively more at risk of, again, obesity, cruciate ligament disease, and possibly diabetes.

With the information above, and I haven’t brought cancers into the equation yet, you might wonder of preventing obesity in desexed dogs might reduce the incidence of cruciate disease and subsequently other conditions that we know are more common in obese dogs, namely cruciate ligament disease and diabetes. You might conclude that there is little benefit to leaving a dog entire if you’re able to control its weight.

I think that’s a reasonable assumption so far, though it’s clear to me that the benefits of traditional desexing are more pronounced in females.

Now lets talk about cancers.

There are multiple types of cancer. Some are more devastating than others. Some are more common than others. In terms of highly malignant cancers that show up relatively commonly in dogs, the ones we talk most about, and of most interest in this topic, are mammary cancer, haemangiosarcoma (HSARC), Mast Cell Tumor (MCT) and osteosarcoma (OSC).

Mammary cancer is extremely common in entire female dogs. In European countries where prophylactic desexing is not routinely performed mammary tumours make up 50-70% of all cancers seen. They are relatively rare in countries with a high desexing rate but extremely predictable in dogs desexed late in life or not at all. Speying earlier appears more protective compared to being left entire: speying before the first heat reduces risk to 0.05%, before second heat to 8%, and before 3rd heat to 26%. after the third heat there is negligible reduction in risk of mammary cancer compared to intact dogs.

Osteosarcoma may be three times (3x) more common in desexed large breed dogs.

Mast Cell Tumors maybe up to three times (3x) more common in desexed dogs of certain breeds.

Lymphoma may be up to 10% more common in desexed dogs of certain breeds.

Haemangiosarcoma may be more common in neutered dogs of some breeds, but less common in neutered dogs of other breeds.

There isn’t much consensus across ALL dog breeds in ALL situations. There are numerous retrospective studies, and more coming out all the time (Science!) but more data needs to be analysed.

What is fairly clear is that there is a dramatic reduction in otherwise common mammary cancers by early desexing of females. There is probably some benefit in reducing other cancer risks to later desexng, or not desexing, dogs also.

So do you? Or don’t you?

There’s certainly more incentive to desex female dogs, as even pyometra on its own is a sneaky, life threatening condition. I recommend desexing most female dogs in their senior years if they haven’t already been done for this reason alone.

Assuming you do chose to desex, and I’m talking about procedures that involve at least removal of the gonads, it becomes a matter of when. If you don’t remove the ovaries then you have no benefits from desexing other than infertility. There’s no significant benefit in leaving the ovaries compared to leaving the dog entire.

For a small dog, OSC is incredibly rare. HSARC is rare. MCT can happen to anything. We weight up those relatively low risks compared to the very high risk of mammary cancer and pyometra, and I would advise speying before the first heat. With males timing is not as critical unless behavioural factors are involved.

For a larger dog, I personally think it’s worth delaying desexing to between the first and second heat. I would get too nervous about mammary cancers to wait beyond the second heat but there may be some benefit in preventing osteosarcoma by delaying surgery until more skeletal maturity, and same for cruciate injuries.

(I have a theory that osteosarcoma occurs in its predilection sites due to increased bio-mechanical forces in these areas, so waiting for skeletal maturity before removing the gonads might be helpful.)

On the other hand, screening for hip dysplasia and desexing if the dog definitely has it so you can perform a JPS also has benefits, because you’re addressing pathology the dog definitely has right now.

There are so many unknowns in these hypothetical scenarios. This makes it a challenge to make recommendations when clients just want the ‘right’ answer.

The best plan for the individual dog may depend on breed or breed mix (genetic testing would be ideal, but an added cost) or any known predispositions within the family or bloodlines.

So, this explanation is getting rather long, but there’s so much interesting information on this topic and it’s growing all the time.

TL:DR there is probably a benefit to delayed desexing in dogs prone to OSC, cruciate injury and HSARC. Some of the other risks may be mitigated by weight control. There is minimal if any benefit, and definitely some risk, in delaying desexing for small breeds.

But this field may change as more information is gathered. It will be worth watching over the next decade.

NB: shelters and rescues will always desex as young as possible, because their primary aim is population control. They are justified in doing this and their cases shouldn’t be considered in these scenarios.

(Majority of these statistics come from ‘The spay/neuter controversy’ presented at the OVMA by John Berg, DVM, DACVS and ‘Long-term health effects of neutering dogs: comparison of Labrador Retrievers with Golden Retrievers‘ by Hart, Hart, et al)

You can spay a dog at any time. Technically. You don’t really want to perform a spay at parturition if you can avoid it, but sometimes in dystocia (difficult birth) you just have to remove the badly damaged uterus. Sometimes this is medically necessary at the time of a caesarian, sometimes it’s done out of convenience.

At parturition, or heavy pregnancy, the uterus is vastly bigger, the blood supply is generous, and there’s all these leaky mammary glands in the way. The ovarian ligaments are a little looser but you have a lot more work to do managing that enormous uterus.

The longer you wait after parturition, the smaller the mammary glands will be, the smaller the uterus will be, and the uterine blood vessels will shrink. The ovarian ligaments remain a little looser then pre-pregnancy, and will never shrink all the way back to its pre-puberty size.