There are two forms: open pyometra, where pus drains through the cervix as a foul vaginal discharge, and closed pyometra, where pus accumulates with no external drainage, creating higher risk of uterine rupture and sepsis. Symptoms include lethargy, excessive thirst, vomiting, swollen abdomen, and fever. Closed pyometra is a surgical emergency. Treatment is almost always an emergency spay (ovariohysterectomy) combined with IV fluids and antibiotics. Without surgery, pyometra is often fatal. Spaying before the first or second heat cycle essentially eliminates the risk, which is one of the strongest arguments for early spaying of non-breeding females.