Glossary

Pyometra

A life-threatening bacterial infection of the uterus in unspayed female dogs, usually in the weeks after a heat cycle, and a surgical emergency.

Also called: infected uterus, womb infection, uterine infection

Pyometra means pus in the uterus. After each heat cycle hormones prepare the uterus for pregnancy, and in an unspayed older female the lining can thicken, allow bacteria to grow and fill the uterus with infected fluid. It usually appears within about two months after a season.

Signs are drinking and urinating more, lethargy, loss of appetite, vomiting, fever and sometimes a foul vaginal discharge. In a closed pyometra no discharge appears, which makes the dog look sicker while the swollen uterus risks rupturing.

It needs urgent veterinary treatment, and surgery to remove the uterus is the usual answer. Spaying prevents it entirely, which is one of the health reasons vets discuss the procedure. Any unspayed female that seems unwell after a heat deserves a same-day call to a vet.

Last reviewed November 8, 2026

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Related terms

Spay Surgery that removes a female dog's ovaries, and usually the uterus, to prevent pregnancy and heat cycles and eliminate the risk of pyometra. Blood panel A set of blood tests that counts blood cells and measures organ-related chemicals, used to screen healthy dogs and investigate illness. Ultrasound A real-time imaging test that uses sound waves to show a dog's organs, heart and pregnancy without radiation.