Pyometra

What is it?

Pyometra is a bacterial infection of the uterus driven by hormone changes after heat. Repeated cycles of high progesterone without pregnancy thicken the uterine lining and can form cysts that make an ideal place for bacteria. It can affect any unspayed female but is most common in older dogs. It usually appears four to six weeks after heat, though it can occur two to sixteen weeks after. Hormone medications containing progesterone or estrogen can also raise the risk.

What signs should I watch for?

If the cervix is open, pus (often bloody) drains from the vulva and may be seen under the tail or on bedding. If it is closed, pus builds up, the belly may swell, and dogs become very ill quickly. Other signs include lethargy, poor appetite, vomiting or diarrhea, and drinking and urinating more. Any very ill unspayed female that is drinking more than usual should be checked for pyometra.

How is it diagnosed and treated?

Blood tests, urine tests, X-rays, and ultrasound help confirm it. The preferred treatment is surgery to remove the infected uterus and ovaries (spay), with intravenous fluids and antibiotics; this is more complex than a routine spay. Medical treatment with prostaglandins may be considered for some breeding dogs, but it is slower, has side effects, carries a risk of uterine rupture (higher with a closed cervix), and pyometra often comes back.

Can it be prevented, and what's the outlook?

• Without treatment, pyometra is often fatal, and a closed uterus can rupture.
• Dogs diagnosed early do best with surgery.
• Any unspayed female given hormones should be watched closely.
• Dogs treated medically should be rechecked about two weeks after treatment, and Merck advises spaying them once their breeding life is over because pyometra eventually recurs.