Vet Lessons

Sick dogContinuing on from my regular Nerdy Vet feature on a clinically relevant topic, this month I was reminded of an all too common condition that we see in small animal practice and which can be easily prevented. Unfortunately it is a problem that many pet owners are simply unaware exists and a lot find out for the first time when their pet is admitted to hospital for investigation and subsequent treatment, all costing a fair amount of money and anxiety for all concerned. What is it we’re talking about? Well, this month our vet lesson is on….


This literally translates as ‘pus’ (pyo) and ‘uterus’ (metra) so no prizes for guessing that it refers to an infection of the uterus, with the vast majority of cases we see in practice being in non-spayed bitches shortly after the end of their most recent season. The reason for this classic timing is to do with the changes in uterine environment and conditions associated with the hormones of oestrus, resulting in a really nice, nutrient rich environment for bacteria to proliferate with less hassle from the immune system. This doesn’t necessarily lead to trouble assuming that the body’s defences can keep any infection in check and clear it up once the animal finishes oestrus and all things return to ‘normal.’ It is highly likely that many dogs have bacteria present in their uterus around the time of heat, simply as a result of their cervix being wide open to the world, but thanks to the wonders of immunity and the fact that bad luck tends to occur far less than some pessimists might have us believe, they get on with life and no problems arise.

There are two main types of pyometra that we might consider. The first is what we refer to as an ‘open’ pyo, in which the cervix is still open and pus can, and does, freely drain from the uterus. This one is generally much easier to a) diagnose (they have pus dribbling from their bits!) and b) treat, as they will often respond well to antibiotics with the safety of being able to monitor the improvement (pus clears up generally equals dog better). I would then recommend neutering that bitch at the next suitable opportunity, most likely several weeks later once everything has involuted and it becomes a ‘safer’ surgical procedure to perform, as our standard advice on spay timing.

The bad boy scenario is the second type, which we refer to as a ‘closed’ pyo. Imagine having an infection raging on behind closed doors, in this case a closed cervix. The uterus, being an organ of finite capacity, fills with pus and expands. The result is an inflamed, pus filled, very unhappy uterus, with the bitch eventually showing signs of general illness. Some will present with signs much sooner than others, with some bitches apparently being as hard as nails and looking fine clinically in spite of having an abdomen full of pus-filled uterus! The bacterial toxins that are produced by the infection can enter the blood and lead to a host of clinical signs, including an increased thirst, malaise and lethargy, vomiting, diarrhoea, and generally just being off their food and out of sorts.


The normal presentation is a bitch who has been generally off colour for a little while and who has a history of being in season within the past few weeks, although pyometra can occur at any time so should always be considered a differential in un-neutered females. They may have clear aberations in their clinical parameters, such as congested mucus membranes, or tachycardia (higher than normal heart rate), and will often be reported as drinking more than normal, off their food and possibly even nauseous, all fairly non-specific signs of illness. If suspected, then a blood test, including haematology to check white cell count, is a good idea, as is an ultrasound scan. Classic cases will show a marked elevation in white cell numbers, especially neutrophils, which are like the riot police of the immune system, being the first to pile on in to areas of infection to start the fight. A scan will usually, but not always, especially if it is a ‘small’ pyo, show fluid filled loops of uterus, with a floculent (think static on your TV) appearance, as opposed to a nice dark liquid appearance. Such changes would be enough to advise rapid treatment.


In some cases, where there is considered to be no risk of uterine rupture, and where the cervix is open, allowing pus to freely drain out of the body, medical management can be considered as an initial measure, the aim being to bring the infection under control and reduce the size of all structures involved in preparation for surgery to neuter as per a normal elective procedure. This usually takes a couple of weeks and can be a very nice way of managing the patient. The cost is possibly a little less than immediate, emergency surgery, although when you factor in the revisits, medication used and the possibility of the animal not responding as planned, then the costs are often very similar. Most cases of confirmed pyometra are still taken to surgery immediately, in order to remove the infected uterus and ovaries (ovariohysterectomy) and thus solve the problem straightaway. These patients would be given antibiotics, anti-inflammatories and intra-venous fluid therapy both prior to, during, and if necessary, after surgery, and would almost certainly go home with antibiotics and anti-inflammatories. Most, if managed sensibly by their owners at home, recover very well and within a week are the bright, happy, appetant animals that their owners remembered having. It is a very satisfying surgery to perform as you know that what you’re doing is making an immediate and clear difference to the chances of that patient surviving and recovering.


Pyometra, infected uterus, surgery

Infected, pus filled uterine horns being surgically removed from a bitch.

In terms of the surgery itself, the approach is the same as for a standard spay, with a midline, ventra (belly) approach to the abdomen and careful incision into the abdominal cavity. The risk with these compared to standard neutering ops is that the uterus is often very distended and may be punctured on your approach into the abdomen itself, which would be a disaster. Once safely in the abdomen, it is usually very easy to find the uterus (look for the big, fluid filled loops of ‘sausages’). Thus starts the very careful task of exteriorising the loops and finding the ovarian pedicles (the ligamental and vascular attachments of the uterus and ovaries to the kidneys on both sides. The risk is that the turgid, fragile uterus could rupture at any moment, spilling it’s toxic contents into your patient and effectively signing their death warrant, so we handle the tissues as if they were made of rice paper, with gentle, smooth movements and avoiding anything that could result in them being torn or punctured. Having an assistant can be extremely helpful in such situations. The ovarian pedicles are clamped and ligated (I personally prefer to transfix, which means I anchor my ligatures in the pedicle itself) and the ovary and uterus separated from it’s attachment, allowing the safely ligated pedicle to be returned to the abdomen. The same is repeated on the other side, followed by the careful clamping and ligating of the cervix. Once free of all attachments my aim is to get that horrid pus filled uterus as far away from my surgical site as I can, but doing so very carefully as it can still rupture and spoil the party at the last minute. Once it’s out of the danger zone, then assuming we have no bleeding or other issues, the abdomen is closed as per usual and the patient recovered.


Neutering. Simple. Unless owners are planning to breed their bitches then there really is little good reason why they should need to remain entire. Ask any owner who was hesitant about spaying their bitch before they had a pyo what their thoughts on neutering are afterwards, then I would confidently guess that the vast majority would be strong advocates of neutering. Yes it can be risky surgery but then developing pyometra, or mammary cancer for that matter, is no walk in the park either and both can be prevented by the application of veterinary knowledge and skill.

So, there you have it. Pyometra is this month’s Vet Lesson and is one you are bound to see at some point during your time on work experience.