Pyometra in Dogs

In its simplest terms, pyometra is an infection in the uterus. Most cases of pyometra are much more difficult to manage than a routine infection.Infection in the lining of the uterus is established as a result of hormonal changes. Following estrus (heat), progesterone levels remain elevated for 8-10 weeks and thicken the lining of the uterus in preparation for pregnancy. If pregnancy does not occur for several estrus cycles, the lining continues to increase in thickness until cysts form within it. The thickened, cystic lining secretes fluids that create an ideal environment in which bacteria can grow. Additionally, high progesterone levels inhibit the ability of the muscles in the wall of the uterus to contract.

Pyometra may occur in young to middle-aged dogs, though it is most common in older dogs. After many years of estrus cycles without pregnancy, the uterine wall undergoes the changes that promote this disease.The typical time for pyometra to occur is about 1-2 months following estrus.

The clinical signs depend on whether or not the cervix is open. If it is open, pus will drain from the uterus through the vagina to the outside. It is often noted on the skin or hair under the tail or on bedding and furniture where the dog has laid. Fever, lethargy, anorexia, and depression may or may not be present.If the cervix is closed, pus that forms is not able to drain to the outside. It collects in the uterus causing distention of the abdomen. The bacteria release toxins which are absorbed into circulation These dogs often become severely ill very rapidly. They are anorectic, very listless, and very depressed. Vomiting or diarrhea may be present.Toxins from the bacteria affect the kidneys ability to retain fluid. Increased urine production occurs, and the dog drinks an excess of water. This occurs in both open- and closed-cervix pyometra.

The preferred treatment is to surgically remove the uterus and ovaries. This is called an ovariohysterectomy (spay). Dogs diagnosed in the early stage of the disease are very good surgical candidates. The surgery is only slightly more complicated than a routine spay. Most dogs are diagnosed when they are quite ill so the surgery is not as routine as the same surgery in a healthy dog. Intravenous fluids are often needed before and after surgery. Antibiotics are given for 1-2 weeks.