What is Pyometra? Pyometra is a secondary infection that happens as a result of hormonal changes in the female dog/cat’s reproductive tract. Following estrus (heat), the progesterone hormone remains elevated for up to two months causing the lining of the uterus to thicken as it prepares for pregnancy. If pregnancy does not occur for several consecutive estrus cycles, the uterine lining continues to increase in thickness until cysts start to form within the uterine tissues (a condition called cystic endometrial hyperplasia). The thickened, cystic lining secretes fluids that create an ideal environment for bacterial growth.

Due to the thickening of the uterine wall and high levels of progesterone the muscles of the uterus cannot contract meaning that the bacteria that enters the uterus and fluids that have accumulated, cannot be expelled.

When does this occur? Pyometra can occur in any sexually intact female young to middle-aged dogs, but is seen frequently in older dogs. Pyometra usually occurs 2-8 weeks after the last heat cycle.

Clinical Signs: The clinical signs depend on whether the cervix is open or not. If it remains open, the pus will drain from the uterus through the vagina to the outside. Pus is usually noted to be seen on the skin, on the hair under the tail or on bedding/furniture where the dog tends to lay down. Symptoms can include fever, lethargy, anorexia and depression but may not always be present. If the cervix is closed, the pus that’s formed is not able to drain and accumulates in the abdomen. The bacteria then releases toxins that get absorbed into the bloodstream. With closed pyometra, dogs quickly become ill often experiencing anorectic, lethargy and depression. Vomiting/diarrhea may sometimes be present.

Diagnosing/Treatment: Dogs with pyometra likely have an increased elevation of white blood cells. A closed pyometra should be ruled out with radiographs to identify an enlarged uterus. With an open pyometra, radiographs are sometimes inconclusive as there is minimal uterine enlargement so ultrasound can sometimes be the better alternative to confirming. Treatment involves surgically removing the infected uterus and ovaries by performing a spay (ovariohysterectomy). Dogs that are diagnosed early enough are likely good candidates for surgery. Dogs diagnosed later when they are already quite ill can possibly endure a more complicated surgery and a longer hospital stay. IV fluids are given intravenously and are required to stabilize the dog during surgery and antibiotics to follow going home.