Pyometra is an accumulation of pus in the uterus. It is a serious, often fatal infection commonly seen in older un-spayed female dogs and less frequently in cats. Common clinical signs include excessive water consumption and urination, depression, and appetite loss. Ovarian hysterectomy (spay) is the recommended therapy.

Most cases of pyometra develop spontaneously from the combined effects of estrogen and progesterone (hormones produced by an animal’s ovaries) on the lining of the uterus. The hormones stimulate an increase in the number of glands in the uterus and suppress the natural defense system allowing an infection to ensue.