Pyometra in Dogs: Symptoms and How Vets Diagnose It

Pyometra is a bacterial infection that fills the uterus with pus, and in an unspayed female dog it is a genuine emergency. If your dog is unspayed and she is drinking more than usual, vomiting, refusing food, unusually flat, or passing a thick or foul-smelling discharge from the vulva, call your veterinarian or an emergency clinic now rather than waiting until morning.

The symptoms most owners notice are increased thirst and urination, lethargy, loss of appetite, vomiting, a distended or tender belly, and vaginal discharge that may be creamy, yellow-green, brown or blood-tinged. The infection usually develops in the weeks following a heat cycle, when hormonal changes in the uterine lining create conditions bacteria can exploit. Pyometra is a surgical emergency in most dogs, and the gap between the first vague symptom and a dog becoming critically ill can be very short.

The signs that mean you should call the clinic today

Pyometra rarely announces itself. The first thing many owners notice is simply that something is off: a dog who normally hoovers her dinner walks away from it, or she is asking to go outside at night when she never used to.

The signs veterinarians ask about most often include:

• Drinking noticeably more water and urinating more often, sometimes with accidents in the house
• Lethargy, weakness, or reluctance to walk or climb stairs
• Loss of appetite over a day or two
• Vomiting, sometimes with diarrhoea
• Vaginal discharge, which may be purulent, mucoid, brown, pink or frankly bloody, and often has a strong smell
• Excessive licking at the vulva, or discharge marks on bedding
• A swollen, firm or painful abdomen
• Panting, a fever, or in a seriously ill dog a subnormal temperature and pale gums
• Collapse

Timing is one of the strongest clues. Pyometra most often appears in the weeks after a season, and it is far more common in older intact females, though a young dog can be affected. Research suggests risk rises as a dog goes through repeated heat cycles because the uterine lining changes with each exposure to progesterone. Dogs that have received hormone injections are also at higher risk.

A dog that has been fully spayed is very unlikely to develop pyometra, although a small remnant of uterine tissue left after surgery can occasionally become infected, which vets call a stump pyometra. If you are unsure whether your dog was spayed, say so at the clinic, because it changes what the vet is looking for.

Open and closed pyometra do not look the same

This distinction matters more than almost anything else on this page.

In open pyometra, the cervix is open, so infected material drains out. That is the discharge owners see on bedding or under the tail. It is unpleasant, but it is also a warning sign that sends most owners to the clinic early.

In closed pyometra, the cervix is shut. Nothing drains. Pus accumulates inside the uterus, which stretches, and bacterial toxins are absorbed into the bloodstream. These dogs often have no discharge at all. They look systemically unwell instead: vomiting, profound lethargy, a swollen abdomen, fast breathing, collapse. Closed pyometra tends to make dogs sicker faster, and because the single most recognisable symptom is missing, it is the version that gets missed at home.

So the absence of discharge is not reassurance. An unspayed female who is suddenly drinking gallons and cannot be roused for a walk needs to be seen whether or not anything is coming out.

Can you feel it at home, and is it painful?

Owners often ask whether they can feel a pyometra by pressing on the belly. Sometimes a veterinarian can feel an enlarged, fluid-filled uterus during a careful abdominal examination, particularly in a smaller or thin dog. But palpation is not a home test, and it is not a reliable one even in trained hands. A full uterus can be mistaken for other structures, an obese or tense dog may hide it completely, and a very distended uterus is fragile. Firm prodding risks rupturing it and spilling infected material into the abdomen, which turns a serious problem into a far worse one. Look, do not press, and get her to the clinic.

As for pain: yes, pyometra is uncomfortable and often painful. Dogs with a distended, inflamed uterus may stand hunched, resist being picked up, flinch when the belly is touched, or simply become withdrawn. Dogs are also skilled at masking discomfort, so a quiet dog is not necessarily a comfortable one. Pain control is part of how veterinary teams manage these cases, both before and after treatment.

Pyometra or a urinary tract infection?

This is one of the most common points of confusion, and for good reason. Both conditions can cause increased urination, straining, licking at the back end and discharge that an owner finds on bedding. The two can even occur together. Only a veterinary examination with the right tests can separate them.

Feature	Pyometra	Urinary tract infection
Who is affected	Almost always unspayed females, often within weeks of a heat cycle	Any dog, spayed or not, any sex
Discharge	From the vulva; pus-like, may be bloody or brown, often strong smelling	Usually none; changes are in the urine itself
Systemic illness	Common: vomiting, appetite loss, collapse, fever or low temperature	Often mild; many dogs stay bright and eat normally
Abdomen	May be distended, firm or painful	Usually normal, though the bladder may be tender
Urgency	Emergency; surgery is usually needed	Serious but generally treated as an outpatient
Typical findings	Fluid-filled uterus on imaging, inflammatory changes on bloodwork	Bacteria and inflammatory cells in a urine sample

One practical note: in a dog with a suspected pyometra, vets are cautious about collecting urine with a needle through the abdominal wall, because the enlarged uterus can be punctured. That is one reason the diagnostic order matters and why self-assessment at home is not an option here. Talk to your vet rather than treating a presumed urinary infection with anything left over in the cupboard.

How vets confirm pyometra: bloodwork, ultrasound and x-rays

Many owners search for pyometra pictures, hoping to compare a photo of discharge with what they are seeing. Photographs cannot confirm or rule out pyometra, because discharge varies enormously and closed cases produce none at all. What is genuinely useful is taking a photo of any discharge on your phone and showing it to the veterinary team, since discharge often stops between episodes.

Diagnosis usually combines several steps:

History and physical examination. The vet will ask when her last season was, whether she is spayed, what she is drinking, and what has changed. They will check temperature, gum colour, hydration, heart rate and abdominal comfort.

Blood tests. A complete blood count often shows a marked inflammatory response in the white cell line. Biochemistry can reveal raised kidney values, altered proteins and electrolyte disturbances. These results also tell the surgical team how stable she is before anaesthesia.

Ultrasound. Ultrasound is the imaging test vets generally rely on. It shows the uterus directly as a fluid-filled, often convoluted tubular structure, gives a sense of the character of the fluid and the thickness of the uterine wall, and helps distinguish pyometra from a pregnancy or from other causes of uterine fluid.

X-rays. Radiographs can show an enlarged, tubular soft tissue structure in the lower abdomen displacing the intestines. They are helpful, but less specific than ultrasound, especially early on or when the uterus is only mildly distended. A normal looking x-ray does not rule pyometra out.

Vaginal cytology and culture. Examining and culturing discharge can identify the organisms involved, commonly Escherichia coli, and guide antibiotic selection.

Treatment, recovery and the risk to the kidneys

The definitive treatment for pyometra in most dogs is surgical removal of the infected uterus and ovaries, supported by intravenous fluids, antibiotics and pain relief. It is a spay, but performed on a sick patient with a fragile, infected organ, so it carries more risk and costs more than a routine neuter. Costs vary widely by clinic and region, and the out-of-hours setting adds to it.

Medical management using drugs that open the cervix and empty the uterus is sometimes considered for a stable dog with open pyometra who is a valuable breeding animal. It is not suitable for every case, it is not usually appropriate for a closed or critically ill patient, and recurrence at a future season is a real concern. That decision belongs with your veterinarian, who can weigh her bloodwork, her imaging and her breeding future together.

Kidney involvement is the complication owners ask about most. Bacterial toxins released during a pyometra can interfere with the kidneys' ability to concentrate urine, which is part of why these dogs drink and urinate so much, and in more severe cases they can contribute to acute kidney injury. Dehydration from vomiting compounds it. This is why intravenous fluid support and repeat bloodwork are standard, and why delays matter: kidney function that is supported early often improves, while a dog who arrives in septic shock faces a much harder course. Results vary from dog to dog, and your vet will monitor kidney values after surgery rather than assuming they return to normal immediately.

Most dogs who are diagnosed and treated promptly recover well and go home within a few days, with restricted activity and a follow-up check. Spaying before a dog is at risk removes the possibility of pyometra altogether, which is one of the points worth discussing with your veterinarian when you plan her care.

Key takeaways

• Pyometra is a pus-filled uterine infection in unspayed female dogs and it is an emergency, not a wait-and-see problem.
• Core symptoms are increased thirst and urination, lethargy, appetite loss, vomiting, a swollen or painful abdomen, and foul-smelling vaginal discharge.
• Closed pyometra produces no discharge and often makes dogs sicker faster, so the absence of discharge means nothing.
• It can look like a urinary tract infection, but the systemic illness, the vulvar discharge and the recent heat cycle point elsewhere.
• Ultrasound is the most informative imaging test; x-rays can support the diagnosis but a normal film does not exclude it.
• Kidney values are checked because bacterial toxins and dehydration can injure the kidneys.
• Surgery to remove the uterus and ovaries is the usual treatment, with fluids, antibiotics and pain relief alongside it.

Your veterinarian owns the diagnosis and the treatment plan here. Pyometra is confirmed with examination, bloodwork and imaging, and it is resolved with veterinary treatment, not with anything you can do at home. If you are reading this at two in the morning because something about your unspayed dog feels wrong, that instinct is worth acting on: call the emergency line and describe what you are seeing.

For a wider look at the signs that warrant an unplanned trip to the clinic, see Dog Emergency Signs.