Current Vet

In this episode of Current Vet, Dr. Lottie talks about canine pyometra, what the underlying physiology is that leads to it developing, the two key types of disease and why it is an emergency.

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Timeline:
00:00 Intro
00:52 Case
01:32 Aetiology & Pathogenesis
03:33 Clinical Signs
04:29 Diagnosis
06:55 Treatment
11:19 Prevention
12:53 Key Points
13:59 Outro

References

Current Vet is an educational podcast intended for veterinary students, veterinary professionals, and individuals with an interest in veterinary medicine.

All content provided in this podcast and its associated materials is for educational and informational purposes only. It is not intended as, and must not be considered a substitute for, professional veterinary advice, diagnosis, or treatment.

Any clinical cases discussed in this podcast are fictional, and are designed to reflect typical or likely clinical scenarios for educational purposes. They do not represent specific real-life cases, clients, or animals.

While every effort is made to ensure accuracy and alignment with current evidence at the time of publication, veterinary medicine is a rapidly evolving field, and recommendations may change over time.

Creators and Guests

Host
Dr. Lottie Wilkinson
Creator and host of the Current Vet podcast

What is Current Vet?

The podcast that makes veterinary medicine simple.

In each episode, Dr. Lottie breaks down clinical conditions, cases, and concepts across species, focusing on pathophysiology, decision-making, diagnostics, and what actually matters in practice. It’s the kind of context that makes your knowledge finally click.

Every month, we’ll also have honest conversations with guests about the incredible variety of veterinary medicine, what you can do with a vet degree and how to think bigger about your career.

Whether you’re cramming for exams or looking for a soundtrack for your dog walk, Current Vet will make veterinary medicine simple

Intro

Hello, hello, and welcome back to Current Vet, the podcast that makes veterinary medicine simple. I'm your host, Dr. Lottie, and today we're covering one of the most common, most important emergencies in small animal practice, and that is canine pyometra.

Just a quick note before we start. Pyometra isn't unique to dogs. It can occur in any intact female, including cats and large animals,

but it's far more common in dogs And in species like cattle. Uterine disease is more typically seen as postpartum metritis or endometritis rather than true pyometra. And of course, it's the last week on our month on canine conditions for June, so today it's focused on dogs. Let's get straight into today's case.

Case

A seven-year-old female entire golden retriever, Bella, is brought into your clinic. Her owner says she's been off food for a couple of days, is very lethargic, and she's been drinking and urinating much more than usual. This morning she noticed a foul-smelling discharge from Bella's vulva and came straight in.

On exam, Bella is dull, dehydrated, and has a slightly distended abdomen, and her temperature is mildly elevated. Straight away, pyometra should be high on your list. And you ask the owner when Bella's last season was, and she thinks it was back in April,

about two months ago.

Aetiology & Pathogenesis

So what is pyometra? As always, I love etymology. I love knowing what the name means, and the name pyometra tells you exactly what is going on. So pyo refers to the Greek word pyon, which means pus, and metra is, or metra is the Greek for uterus or womb. So pyometra literally means a pus-filled uterus.

There are two key elements to the development of pyometra. First is high progesterone levels, and second is bacterial infection. So during the luteal phase or diestrus, progesterone levels are at their peak. Progesterone is gonna do three things that encourage pyometra to develop So first it stimulates endometrial gland secretion and hyperplasia.

It then suppresses contractions in the myometrium, which is the muscular layer of the uterine wall. And thirdly, it actually suppresses local immunity. So when a female goes through repeated cycles where they aren't getting pregnant and this environment is developing with repeatedly getting these high progesterone levels, it results in cystic endometrial hyperplasia, which basically means that the uterus becomes more prone to infection.

Bacteria ascend from the vagina and colonize the uterus, and the majority of cases are caused by E. coli, but some other bacterial species like Klebsiella or Proteus, Staphylococcus, Streptococcus can also cause pyometra. The result of this is essentially that pus-filled uterus, which if left untreated can cause further systemic illness as bacteria and bacterial toxins can spread through the bloodstream.

Clinical Signs

So the clinical signs are gonna vary depending on whether the cervix is open or closed, and this is where the condition can be categorized as either an open or a closed pyometra. So with an open pyo, it is often a less severe presentation as the pus actually has somewhere to drain out. So we aren't getting quite the same buildup of pus, but we're going to see the foul-smelling vulval discharge, the lethargy, and inappetence associated with just general infection.

Closed pyos can be much more dangerous. Because the cervix is shut, no discharge is gonna be visible, and there's nowhere for the pus to drain. So these dogs typically present with polyuria, polydipsia, vomiting, lethargy, pyrexia, inappetence, or even endotoxic shock from sepsis.

Diagnosis

How are we gonna confirm pyometra in cases where we suspect it? So first up,
the signalment and history is gonna be a big clue. So when we have entire females that are middle-aged or older, and they're around one to two months post-oestrus, so firmly in that di-oestrus phase, your alarm bells should be going off. Owners often report that lethargy, inappetence, vomiting, vulval discharge, and PUPD.

Then on clinical exam, we see that dull, dehydrated

presentation. and a couple of signs of more severe disease or sepsis are going to be tachycardia, weak pulses, prolonged capillary refill time, and then potentially hypothermia and collapse.

Once we suspect pyometra, we often jump straight to imaging for diagnosis, and an ultrasound is going to be the most useful tool. So you typically see enlarged uterine horns. They are going to be fluid-filled, so typically anechoic and black and a thickened uterine wall.

This is also really great for differentiating the condition from potentially pregnancy or free abdominal fluid, or you can assess if actually there is pyometra and it's potentially ruptured into the abdomen. So it's a really good way of ruling out differentials and assessing the extent of pyometra if present.

Radiography is also possible. It's less sensitive than ultrasound as it doesn't show the soft tissue structures as well. But you may see soft tissue tubular structures in the caudal abdomen, which is going to indicate pyometra.

We can then also do blood work, so hematology and biochemistry. Hematology, probably going to see a leukocytosis caused by inflammation and the infection. Neutrophilia with a left shift, possibly toxic neutrophils, and then maybe a mild non-regenerative anemia.

On biochemistry, we often see azotemia, hypoglobulinemia, possibly hypoalbuminemia, and then electrolyte disturbances, especially if there's vomiting.

Treatment

Okay, let's assume we've performed an ultrasound scan on Bella, and you've seen the typical kind of sausage-shaped uterine horns. How are we now going to treat her? Pyometra is a surgical condition, and the treatment of choice is an ovariohysterectomy, which removes both the ovaries and the uterus. So it's basically it's removing the infection and also the risk of recurrence in the future.

But before we think about doing the surgery, we need to stabilize our patients. Many of our patients are gonna be dehydrated or potentially endotoxemic and at risk of shock. So fluid therapy with IV crystalloids are gonna help to correct that dehydration and support and restore perfusion.

Antibiotics can also be started if sepsis is suspected, and we're gonna reach for a broad-spectrum antibiotic, something like amoxicillin-clavulanate. Okay, so once they are stable, we can then consider going into surgery. And as we said before, the ovariohysterectomy is gonna be the gold standard.

There are a couple of considerations, though. This is not gonna be a typical routine spay procedure. The uterus is enlarged. It's gonna be friable. It's much more at risk of rupture, and of course, it's filled with pus. So if it does rupture, it then means leakage of infection and spread of infection into the abdomen. Which is then gonna cause peritoneal contamination and then potentially septic peritonitis. So couple of key intraop principles are gonna be really gentle tissue handling. We want to make sure we're avoiding tissue rupture. We want to ligate vessels really securely And double-check, triple-check for any leakage.

If rupture does occur, we can do abdominal lavage and antibiotics, but of course, it's much more preferable if that can be avoided. After surgery, we need to be continuing those IV fluids, continue antibiotics if they have been started, and then make sure we're monitoring the mentation, their appetite, and their blood work.
I am just quickly gonna touch on medical management. So this is not first line in most cases, and it's only really considered if the animal is a breeding animal, so obviously needs the uterus. If
the pyometra is an open pyometra, so that pus is draining out somewhat.

If the animal is systemically stable and if there is no evidence of sepsis. So the number one medication that is used are prostaglandins, so PGF2 alpha, and this causes luteolysis, which then leads to a reduction in progesterone levels. This helps to open the cervix and increase the uterine contractions and just flush out the pus.

We're also gonna give antibiotics and obviously really good supportive care whilst this is going on. There are a lot more risks associated with this. We see vomiting, diarrhea, and panting as side effects from prostaglandins. The infection can worsen if actually it's not fully flushed out.

And there's obviously a much higher recurrence rate because we're not removing the uterus. So basically, surgery is the treatment of choice, and medical management is rarely sufficient and only really considered if the bitch is young, if they're valuable, if they've got an open pyo, and they don't have any signs of sepsis or systemic illness.

It's also recommended that if medical management is used, the bitch should then be bred in her next season because this Then means they're less susceptible to infection and pyometra recurrence.
The prognosis in prompt surgical intervention is generally really good, but untreated pyometra is almost always fatal, and delays in diagnosis give the bacteria that time to spread, leading to sepsis or shock and then eventually death.

Prevention

Before we wrap up, I do wanna mention prevention and the importance of talking to owners about spaying, especially when they have a young puppy.

So of course, the number one way of making sure a dog won't get pyometra is to spay her. A uterus cannot get infected if it isn't there in the first place. The reported numbers are currently that one in four unspayed females will develop pyometra at some point in their life, which is twenty-five percent.

There are, of course, risks associated with any surgical procedure, but these risks are much, much lower in a young, otherwise healthy dog when it is an elective procedure versus if the dog is critically ill and the surgery is an emergency. Just to highlight the fact that nothing we do is perfect, very rarely a condition called stump pyometra can develop if small amounts of the uterine tissue are left behind after spaying, especially if there's ovarian remnant tissue as well, which is producing progesterone.

But essentially, elective spaying is the most effective way to prevent pyometra in dogs.

This isn't to say that absolutely every female dog must be spayed, no question. It's just to highlight the numbers and the risks associated with this condition and to say that there is one very obvious way of eliminating those risks that we as vets have a responsibility to explain to our owners.

Key Points

So what are the key points that you should know about pyometra? Pyometra is the accumulation of pus in the uterus caused by a bacterial infection, and it's most common in older intact bitches during diestrus. Open pyos often have visible purulent discharge, whereas closed pyos present with signs of systemic illness, lethargy, PUPD, and vomiting Diagnosis is mainly based on the history, the clinical exam, and imaging with ultrasound. The best treatment choice is ovariohysterectomy, but remember to stabilize before going into surgery. Medical management is possible, but it carries much higher risks and generally shouldn't be recommended over surgery.

And finally, elective spaying almost entirely eliminates the risk of developing pyometra because the uterus can't be infected when it's not there.

Outro

And that's the end of our episode on pyometra in dogs. Thank you so much for listening. I hope this helps make pyometra feel a little clearer, whether you're revising for exams or you're practicing.

Check out the show notes for further reading and references. And as always, if you have any topic requests or cases that you'd like us to cover, we would love to hear from you. So find us on Instagram and TikTok @veterinaryvista or let us know in the comments below. We'll see you next time