Pyometra in dogs: symptoms and urgent treatment

Overview

Pyometra is an infection inside the uterus that can affect the whole body. The cervix is the opening leading out of the uterus. If it is open, discharge can drain through the vagina. In the closed form, pus remains inside the uterus, and you may see nothing unusual around the genital area.

Visible discharge helps identify the problem, but your dog may also have significant systemic illness. Without treatment, the infection can lead to sepsis and death.

Pyometra is one of the most common reproductive diseases in female dogs. With a closed cervix, the uterus can rupture as pressure increases.

In a Swedish follow-up study of insured female dogs, 19% had developed pyometra by 10 years of age.

Causes

Hormonal changes associated with the reproductive cycle and bacteria entering the uterus underlie the disease. E. coli, which also occurs in the intestine, is a common cause. Bacteria can ascend from the vagina into the uterus while the cervix is more open during a season. Your dog therefore does not need to have been mated, or to have had an unusual exposure that you noticed.

Progesterone affects the uterus during the phase after a season. It increases secretions from uterine glands, reduces uterine contractions and can close the cervix. Local defences also become weaker. Together, these changes can create favourable conditions for bacteria and prevent discharge from draining. This explains why the disease often becomes apparent only after a season.

The uterine lining may also thicken and develop cystic, or fluid-filled, changes. These are called cystic endometrial hyperplasia. The change can be associated with pyometra, but not every case of endometrial hyperplasia progresses to a pus-filled uterine infection.

Oestrogen can increase progesterone receptors in the uterine lining, making the tissue respond more strongly to progesterone. Alongside E. coli, staphylococci, streptococci and Pseudomonas bacteria may be found in the uterus.

Risk factors

Any female dog whose ovaries have not been removed can be affected. The disease is more common in middle-aged and older dogs that have had several reproductive cycles. However, being young does not rule it out.

Tell the vet about hormonal medicines and previous reproductive procedures too. In rare stump pyometra, remaining uterine tissue can become infected, for example when ovarian tissue remains or the dog has received progesterone-like hormones.

Risk rises particularly in unspayed female dogs older than 6 years. Cystic endometrial hyperplasia in a middle-aged or older dog is usually associated with previous seasons not followed by pregnancy.

In the same Swedish study, the average age at diagnosis was 7.0 years. Differences in disease incidence between breeds also suggest a role for inherited factors.

Typical symptoms

Signs often appear 4–8 weeks after a season. You may initially notice only increased drinking or tiredness. Discharge may be pale, pus-like or bloody, but in the closed form there may be none at all.

• Your dog becomes tired or seems duller than usual.

• Appetite decreases or eating stops.

• Drinking and urination increase.

• Abnormal vaginal discharge appears if the cervix is open.

• The abdomen swells or becomes tender, and your dog may vomit.

Fever is possible, but do not wait for every sign on the list before contacting a vet.

The disease often begins about 1–2 months after the last season. Some dogs initially show only a pus-like vaginal discharge as a sign of illness.

Complications and consequences

The infection within the uterus can allow harmful substances produced by bacteria into the bloodstream and cause a severe reaction throughout the body. Sepsis means dangerous organ dysfunction caused by infection. Shock, dehydration and anaemia can also occur.

If the uterus ruptures, the abdominal cavity can become contaminated and the outlook worsen. Severe infection can also be associated with organ damage.

Some dogs may be left with kidney function problems, seen as persistent increased drinking and urination.

After removal of the uterus and ovaries, the chance of survival can be 80–100% if the abdominal cavity is not contaminated and systemic infection responds to appropriate treatment. Severe sepsis and organ failure worsen the outlook.

Cystic endometrial hyperplasia can impair fertility even without a pus-forming infection. Pus leaking into the abdominal cavity can cause peritonitis.

Diagnosis at the vet

The vet asks about the last season, when signs began, drinking and any discharge. General examination assesses your dog's condition and abdominal findings, among other things.

Ultrasound can show an enlarged, fluid-filled uterus and changes in its wall. X-rays may also suggest pyometra, but do not always confirm the diagnosis on their own.

Blood tests assess the inflammatory response and functions including kidney health. White blood cell counts may be increased or, in a severe case, decreased. Urine testing and vaginal cytology may also be included.

The vet may begin stabilising treatment before surgery.

Ultrasound also establishes whether uterine enlargement is due to pregnancy or fluid accumulation without pregnancy. On an X-ray, an enlarged uterus may contain gas as well as fluid. The change is often more apparent when the cervix is closed.

Increased blood urea and creatinine can indicate impaired kidney function. Levels of gamma globulins associated with inflammation may also rise. Cystic endometrial hyperplasia alone does not involve inflammatory discharge, and a dog may show no outward signs.

Treatment

The vet prescribes treatment, and the first-choice approach is usually surgery to remove the diseased uterus and ovaries. Intravenous fluids may stabilise circulation and fluid balance before anaesthesia. Antimicrobial treatment and pain relief form part of care when needed. This is surgery on a seriously ill patient and can be more demanding than a planned spay in a healthy dog.

After removal, your dog can no longer have puppies because the reproductive organs have been taken out.

Monitoring of general condition and possible complications continues after surgery. Some dogs need closer care because of problems such as sepsis, dehydration or circulatory disturbance. Discharge depends on the patient's recovery.

Medical treatment without surgery is considered only in carefully selected circumstances, for example when preserving fertility is desired. It is not a routine alternative for a dog with systemic illness or sepsis. Treatment involves medicines affecting hormones, antimicrobials and close monitoring.

Medical treatment may fail, or the infection may recur after a later reproductive cycle. Emergency surgery is recommended if there is no clear improvement within 48 hours or the condition worsens.

At home, protect the wound from licking with a collar or another covering approved by the vet. Keep your dog quiet and restrict exercise while healing takes place. Give medicines according to discharge instructions and tell the veterinary team about any practical difficulties.

Hormone-based medical treatment can cause effects such as panting, salivation, vomiting and diarrhoea. Uterine rupture is also a possible serious complication.

For 2 weeks after surgery, avoid off-lead running, stairs and normally boisterous play. Protect the wound from licking and other damage your dog might cause.

Treatment affecting hormones aims to open the cervix and allow uterine contents to drain. Some medicines block progesterone's effects by binding to its receptor. Prostaglandins, in contrast, increase uterine contractions.

When prostaglandin treatment is used, blood progesterone is measured before and during treatment. Ultrasound also assesses response: the uterine diameter should decrease and fluid in the cavity disappear. Clinical signs should improve at the same time.

Hospital monitoring after surgery may be needed for 2 days, for example. During recovery, whining, rapid breathing, growling and guarding the surgical area can indicate severe pain.

The need for antimicrobials after surgery is assessed individually. Unnecessary antibiotic use promotes bacterial resistance. Adverse effects of prostaglandin treatment often appear within 20–30 minutes of administration.

Removing the uterus and ovaries also removes the cancer risk in those organs. Pregnancy is no longer possible after their removal.

Prevention

Planned spaying prevents pyometra. Discuss timing and technique with your vet according to your dog's circumstances. Complete removal of ovarian tissue is essential to prevention. Urgent surgery in an affected dog is different from a planned procedure in a healthy dog, so discuss possible prevention before an emergency arises.

If your dog is not spayed, monitor her condition after every season. Record season dates and changes in drinking, appetite or alertness. Monitoring does not prevent infection, but helps identify a possible problem early.

When all ovarian tissue has been removed, reproductive cycles stop.

Important for dog owners

Keep records of seasons, previous operations and medicines. When calling the practice, start with your dog's general condition, then explain whether discharge is present or absent. Photograph any discharge if possible, but do not delay seeking care to obtain a picture or sample. Ask how to transport a weak dog if needed.

Bring details of hormonal products and previous treatments used to suppress seasons. Have the emergency practice's address and transport arrangements ready. Also note the time of the last meal to tell the veterinary team.

Frequently asked questions

Can a dog have pyometra without discharge?

Yes. A closed cervix prevents discharge from draining even while pus accumulates in the uterus. Your dog can then be seriously ill without visible genital discharge. Tiredness, increased drinking, vomiting or abdominal swelling after a season are therefore reasons to contact a vet promptly.

Is pyometra mild if discharge is visible?

Not necessarily. In the open form, discharge can drain out, but your dog can still have systemic illness and a risk of severe infection. Visible discharge is no reason to wait at home; suspected pyometra needs urgent examination.

Can pyometra be treated with antibiotics alone?

Antibiotics alone should not be considered adequate home treatment for typical pyometra. Surgery is usually the first-choice treatment. Carefully selected non-surgical treatment is a separate, monitored approach that may include medicines affecting hormones. The vet determines suitability from your dog's general condition and investigation results.

Can a young female dog be affected?

Yes. The disease is more common in middle-aged and older unspayed females, but is not confined to them. A decline in a young dog's condition after a season also needs investigation. Age is therefore not a safe reason to rule out pyometra at home.

Can the disease return after medical treatment?

Yes, and recurrence is a major risk of non-surgical treatment. The disappearance of signs therefore does not mean your dog is permanently protected. Agree monitoring and a longer-term plan with the vet treating your dog, including which signs mean she must return for examination immediately.