What is Pyometra?

Pyometra is the accumulation of pus inside the uterus, caused by a bacterial infection favored by hormonal changes that occur after a heat cycle (estrus). During this period, the cervix remains partially open and the uterine lining becomes thicker and more vulnerable to bacterial colonization, most often by bacteria such as Escherichia coli. It is most common in middle-aged to older unspayed female dogs and cats, generally 4 to 8 weeks after a heat cycle.

There are two main forms: open pyometra, in which the cervix remains open and purulent discharge is visible from the vulva (easier to notice), and closed pyometra, in which the cervix is closed and pus accumulates inside the uterus with no visible external sign — this form is more dangerous, since the condition can progress rapidly to sepsis before an owner notices anything is wrong. Symptoms include lethargy, loss of appetite, increased thirst and urination, abdominal distension, fever, and, in the open form, foul-smelling vaginal discharge.

Pyometra is a veterinary emergency: without treatment, it can progress to uterine rupture, peritonitis, and sepsis, with a risk of death. Definitive treatment is surgical removal of the uterus and ovaries (ovariohysterectomy), often combined with antibiotics and intensive supportive care. Seek immediate veterinary care if an unspayed female shows lethargy, increased thirst, abdominal distension, or vaginal discharge, especially weeks after her last heat cycle.