Pyometra in Dogs

Pyometra is one of the most serious reproductive emergencies seen in female dogs. It can progress rapidly and become life-threatening within days. The encouraging news is that with prompt veterinary treatment, most dogs recover well.

What is pyometra, and why does it happen?

Pyometra literally means “pus in the uterus.” It is a severe bacterial infection that causes the uterus to fill with infected fluid and toxins. As the infection progresses, toxins can enter the bloodstream and affect organs such as the kidneys, leading to sepsis and potentially death if untreated.

This condition is closely linked to normal hormonal changes that occur during the reproductive cycle of an entire (undesexed) female dog. After each heat cycle, progesterone levels remain high for several weeks. Progesterone prepares the uterus for pregnancy by thickening the uterine lining and reducing the uterus’s ability to contract. At the same time, the immune defences within the uterus are temporarily suppressed.

These normal changes create an environment where bacteria, most commonly E. coli from the dog’s own intestinal tract, can enter the uterus and multiply. Over multiple heat cycles, repeated exposure to progesterone causes progressive thickening and cystic changes in the uterine lining, making infection increasingly likely. For this reason, pyometra is most commonly seen in middle-aged to older dogs and typically develops one to two months after a heat cycle.

Dogs that receive hormone medications containing progesterone or oestrogen are also at increased risk.

Open vs closed pyometra

Pyometra can occur in two forms depending on whether the cervix remains open or closed.

In open pyometra, the cervix is open and infected discharge can drain from the uterus. Owners may notice a foul-smelling discharge from the vulva, increased licking under the tail, or staining on bedding.

In closed pyometra, the cervix is closed, and the infected material becomes trapped inside the uterus. This form is more dangerous because there may be no visible discharge, the uterus can become greatly enlarged, and toxins can rapidly enter the bloodstream. In severe cases the uterus may rupture, leading to life-threatening infection in the abdomen.

Clinical signs of pyometra

Dogs with pyometra often become unwell quickly. Early signs can be subtle, but the condition can deteriorate rapidly over a short period of time.

Common signs include lethargy, reduced appetite, vomiting, increased thirst and urination, and weakness. Some dogs develop a fever, while others may have a normal or even low body temperature. Abdominal swelling or discomfort may be noticed in more advanced cases. Dogs with an open pyometra may also have vaginal discharge that can be bloody, brown, yellow, or cream-coloured and often has a strong odour.

Many owners initially think their dog is simply “not quite herself,” which is why any sudden illness in an entire female dog should be assessed promptly.

How is pyometra diagnosed?

Diagnosis usually involves a combination of clinical examination, blood tests, and imaging.

During the physical examination, your veterinarian may detect fever, dehydration, abdominal enlargement, or vaginal discharge. Blood tests often show evidence of infection and inflammation, as well as dehydration and possible effects on kidney function caused by circulating toxins.

Imaging is essential to confirm the diagnosis. X-rays or ultrasound allow us to identify a fluid-filled, enlarged uterus and assess the severity of the condition.

Treatment

Emergency surgery

The recommended and most effective treatment for pyometra is emergency surgery to remove the infected uterus and ovaries (an ovariohysterectomy). This procedure is similar to routine desexing, but is significantly more complex because patients are often very unwell and the uterus is enlarged and fragile.

Treatment typically also includes:

• Intravenous fluids to treat dehydration and shock

• Antibiotics to control infection

• Pain relief and intensive monitoring

When treated promptly, the prognosis is generally very good.

Medical treatment in breeding dogs

In carefully selected cases, medical treatment may be considered for valuable breeding dogs. This involves hormone injections to empty the uterus combined with antibiotics and very close monitoring. However, this approach is not suitable for severely ill dogs, carries a higher risk of complications, and recurrence is common. If a dog is to receive medical management, it must be bred at the next cycle or the infection will likely return. Many dogs treated medically will still require surgery later in life.

What happens if pyometra is not treated?

Without treatment, pyometra can rapidly lead to septic shock, kidney failure, rupture of the uterus, and death. This is why the condition is considered a true veterinary emergency.

Can pyometra be prevented?

Yes. Desexing completely prevents pyometra. Removing the uterus and ovaries eliminates the possibility of this infection developing. Elective desexing while a dog is young and healthy is much safer and far less risky than emergency surgery later in life.

When should you contact your vet urgently?

Please contact your veterinarian immediately if your female dog has been in heat within the past two months and shows any signs of illness. Sudden lethargy, increased thirst, vomiting, or any vaginal discharge should always be checked promptly.

Pyometra is a serious but treatable condition, and early veterinary care can be lifesaving.