Slide 1 Welcome to this lecture of canine theriogenology. You may have been expecting that I would jump right into things like pyometra, abnormal estrous cycles, vaginal prolapses and so on. But we have something far more important to cover first. We have to look closely at the subject of spay/neuter or in other words, ovariectomy and castration.
Slide 2 Take at look at this for starters. It is the result of a couple of good studies on just what is important to general practitioners in day to day practice. From the points of view of financial importance, frequency of occurrence and need for proficiency. I don't want to diminish the importance of all the fancy stuff like gastric torsion, autoimmune disease, ophthalmology and cardiac problems but truly, they pale when compared to things like anesthesia, spay-neuter and euthanasia. Now I can t talk about anesthesia and I don't want to address euthanasia but I really need to talk about spaying and a little about castration as well.
Slide 3 Here I have tried to emphasize to the points I spoke about in the previous slide. You can see that it is not only the procedures of spay/neuter that I am referring to here but consulting on those procedures with owners as well. When I was in companion animal practice we never discussed any of this stuff with owners but that was not because we didn t care; it was just because we didn t know.
Slide 4 The first thing I want you to realize is that although neutering may seem simple... but it is not. Sure, the technique is pretty straightforward but many things it encompasses can be quite complex. If you have lived long enough, you will have noticed that simplicity is often just a reflection of your inexperience or ignorance. And in this case, we want neither.
Slide 5 In the bad old days we just used to admit dogs, spay or neuter them then tell the owners when to come back to have the sutures removed. There was no thought of discussion potential changes in behaviour, mammary tumors, weight gain, urinary incontinence and so one. Owners found this out for themselves, the hard way, as it happened to their own animals. They deserve be well informed and they should also be prepared for the negative side of ovariectomy and castration; just in case. That kind of consultation builds trust, improves your relationship with your clients and builds your practice.
Slide 6 This table illustrates some of the things you should cover in that pre-surgical discussion with your clients: Here are some of the benefits: Absence of pregnancy is a no-brainer. But unfortunately there are lots of people without brains out there so ovariectomy is not as common as you may think. Ovariectomy causes a dramatic decrease in the incidence of mammary adenocarcinoma; the beneficial effect being greater when ovariectomy is done earlier in the bitch s life. And mammary adenocarcinoma is often fatal, so this is important. Ovariectomy decreases the incidence of pyometra to almost zero; about the same as if the uterus itself is removed. If we include males briefly, when there are no testicles, chronic prostatic enlargement virtually eliminated. Of course, both ovariectomy and castrations have a profound effect on sexual behaviour and naturally this decreases straying and all its attendant risks.
Now for some drawbacks First, ovariectomy is not risk free; if you perform this operation for many years you may lose a patient/s because of anaesthetic or surgical risk. There is also some debate on the effect of ovariectomy on hypothyroidism, weight gain and diabetes mellitus but a consensus of informed opinion suggests that the risk of all of these is only slightly elevated after ovariectomy. With respect to castration, we have to remind ourselves that contrary to expectations, the incidence of prostatic adenocarcinoma actually increases after castration. However, the incidence remains low enough that one should not be dissuaded from castrating dogs. In fact both of my male Schnauzers have been castrated. Owners must be informed that there is increase in sphincter mechanism incompetence causing urinary incontinence. This seems to be a problem in larger breeds and when bitches are ovariectomized late in life and is due to the loss of alpha 2 receptors in the bladder sphincter. The incidence varies from 0.5% to close to 20% but current data strongly suggests that prepuberal ovariectomy actually decreases the incidence of post ovariectomy incontinence. This lends more support to the case for prepuberal ovariectomy; something we will discuss later in this lecture. Some contention still exists over many other conditions and how they relate to ovariectomy. These include the trainability of ovariectomized bitches, some types of neoplasia and cruciate rupture.
Slide 7 Another sequel to ovariectomy is its potential effect on behaviour. Some studies suggest that ovariectomy may lead to aggressive behaviour but others suggest otherwise. Obviously more study is needed and your help is required. That is why this slide introduces you to C-BARQ a long term study on canine behaviour in which any veterinarian can participate. I have actually used this on my own dogs to identify their behavioural quirks and their potential management.
Slide 8 This is typical of a CBARQ report. You can see that they reports are also breed oriented as well.
Slide 9 OK so now we are going to talk about some approaches to ovariectomy First, why not just take out the ovaries and leave the uterus in there? Is there anything wrong in doing so and if not, why doesn t everyone do this? Well first, there is nothing wrong is with just leaving the uterus out of the equations and only removing the ovaries. This has been studied for many years now on thousands of bitches, yet the majority of North American veterinarians continue to do ovariohysterectomies, increasing surgical time, surgical trauma and the risk of injuring the ureters. Most modern European veterinary graduates will now only do ovariectomies. I'm afraid that the reason we still do ovariohysterectomies in North America it is just because of social and academic lethargy and downright ignorance. If this is still done in our veterinary schools one hopes that is it merely to teach students the techniques for hysterectomy. You know we carry around all sorts of dogmas (if you will excuse the pun) about ovariectomies and some of them are as follows:
First...You can t ovariectomize a bitch while she is in heat. This is nonsense. I used to do this regularly when I was in practice and never suffered a surgical loss. One just has to proceed with extra caution, especially in big fat bitches. When it comes to population control, a bitch in the hand is worth two in the bush and the bitch on your operating table is the one you should spay. If you delay the operation, the owners may forget about the inconvenience of red spots on the white carpet and male dogs pooping on the front lawn. The bitch may have an unwanted pregnancy or at the very least will stand a greater chance of having mammary adenocarcinoma when she gets older. Second...You can t ovariectomize a bitch after doing a caesarean section. Again this is nonsense. It may be advisable to remove the uterus in these cases because they contain lochia and risk becoming infected but even that is debatable. Removing the ovaries will have no effect on milk production either. So if you are doing a C-section for an unwanted litter, you should strongly consider removing the genital tract at the same time. Third...It is inhumane to remove a uterus full of unwanted puppies; another bit of nonsense. Consider first that the fetuses are just as anaesthetized as the bitch is because the placenta allows the transfer of both inhaled and injected anaesthetics. Then consider that the fact that ligation of the uterine blood supply only causes depletion of the oxygen supply to the brain and in effect, causes the fetuses to faint. It is not as though you are drowning these puppies. The last time I fainted I can only recall feeling weak before I collapsed, and I didn't even have the benefit of being anaesthetized! Finally...You have to do a midline incision to spay a bitch. Well you may be surprised to know that some European veterinarians make bilateral flank incisions to spay bitches. True, there is more preoperative preparation and one also has to roll the bitch over in the middle of the operations but proponents of doing it this way maintain that the risk of injuring the ureters in minimized and only small flank incisions are required. Remember of course, these people are not removing the uterus either so a midline incision is not required. Finally, endoscopic studies have shown that when the mesovarian ligament is drawn upward towards a midline incision, there is often sub-peritoneal tearing in that region and this causes significant intra-operative pain, reflected by a significant increase in blood pressure. It is likely that this is also a source of post-operative pain as well. If the ovaries are removed via flank incisions, the chances of peritoneal injury are minimized. However when all is said and done I am not really sold on this idea because flank incisions are usually more painful to the animal than those on the ventral midline. Interestingly, some practitioners now only use laparoscopic thermal-cautery for ovariectomies; it is rapid, there is little trauma and there is almost no need to pull up on the mesovarian ligament before ligating it.
Slide 10 OK...so what about ovariectomizing or castrating puppies even before they leave the breeder? Say at about 6 to 12 weeks of age? Wouldn't that be a great way to decrease the number of unwanted puppies and wouldn t it also be a great idea for enforcing no-breeding contracts? Also, wouldn't it be even better from a point of view of preventing mammary adenocarcinoma? The answers are yes, yes and yes. It is probably also beneficial now that we know that urinary incontinence is probably more common after ovariectomy in older bitches than younger bitches; something hotly debated in past years. So why don't we do this at all in some practices and why didn t I do it when I was in practice? Well at least we had an excuse back then; we just didn t know that it could be safe or even that it was a good idea. But nowadays, the young veterinarian in practice has no excuse not to do prepuberal spay/neuters. You remember my statements about ovariectomy vs. ovariohysterectomy? Well it s more of the same plus fear of the unknown. Veterinarians are afraid of anaesthetizing very young puppies and I would be too but that's only because I don't do much surgery anymore. In fact, all reports suggest that this is not risky surgery if appropriate care is taken over things like hypothermia and hypoglycemia and of course the type and route of aesthetic administration. In essence, these tiny animals cannot be starved as long as older
animals because of their tendency to hypoglycemia, and because of their high surface to volume ratio, they must be kept warm throughout the operation. Obviously they have small blood volumes too so strict hemostasis must be observed. The uterus and ovaries are also very small so although they are not really fragile, they can be torn quite easily. Other than that, proponents of prepuberal spay/neuter report than the operation is simple and quick because there is no fat in subcutaneous or abdominal fact and structures are easily identified. Are there any drawbacks? Yes of course, nothing is perfect. The first drawback is that it takes some courage and training to learn how to do this. You also have to consider the effects of sex steroids on epiphysis closure. That is, the later an animal reaches puberty, the later its epiphyseal growth plates will close so this makes for a significantly taller animal when it reaches maturity. But does it result in an excessively gangly and animal and one that is prone to injury? The general consensus is no, just think of all the farm animals that are castrated long before puberty. It is true that prepuberal ovariectomy can sometimes result in peri-genital dermatitis because juvenile vulvas become surrounded by skin folds but fortunately that is not common and it can be controlled in most cases by careful feeding, in other words by preventing obesity. Slide 11.. OK, that's all for now...