Pyometra in Dogs

    Pyometra is a life-threatening condition found in intact female dogs. The word pyo means pus and metra means uterus so the translation is a pus-filled uterus. This condition usually occurs in middle age to older females about four to twelve weeks after a heat cycle. During estrus or heat, the cervix opens to give sperm access to the ovulated eggs. Unfortunately, the open cervix allows bacteria to enter as well. After the cycle is over, the cervix closes again as the female’s hormones change from high levels of estrogen during heat (estrus) to high levels of progesterone during the periods between heat cycles (diestrus). Progesterone causes the uterine walls to hypertrophy giving bacteria a perfect place to colonize.  It also inhibits the function of white blood cells in the uterus that fight bacteria. With each heat cycle, the hypertrophy and immunosuppression increase until a pyometra develops.  
    Common signs of pyometra in dogs are increased thirst and urination, vomiting, depression and anorexia. Diagnosis is easy in dogs with an open cervix that allows the pus to escape.  Most owners will observe the discharge and bring the dog in for treatment. In patients with a closed cervix, the pus is trapped in the uterus causing it to swell. Diagnosis requires an ultrasound or x-rays to see the fluid-filled loops of the distended uterus.(Pictured below is the rear end of a dog with an open cervix pyometra.)

    Treatment is simple, spay the dog immediately.  Unfortunately, that is easier said than done. These girls are really sick. They usually require fluid therapy and sometimes blood or plasma transfusions to get them stable for anesthesia.  In addition, the uterus may rupture contaminating the dog’s abdomen. I have never been able to save a dog after this has happened.  Other complications include septic shock and renal failure. (Pictured below is a pyomentra after surgical removal. I incised the uterus after it was safely removed from the patient for demonstration purposes. The bright green material is pus.)

    To prevent a pyometra from developing, I recommend spaying all non-breeding dogs. A routine spay is much less expensive than an emergency spay with a prolonged hospitalization. It is also safer for the dog. In my opinion, medical management should only be tried in cases of open cervix pyometra. The female is given prostaglandins to cause leuteolysis, thereby decreasing progesterone. The prostaglandins also stimulates uterine contractions to expel the pus and improve uterine immunity. I do not recommend this treatment for cases of pyometra with a closed cervix as the uterus could rupture.  


Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.

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