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208 Breeds, 422 Health Conditions  |  Find a Vet

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Pyometra and Cystic Endometrial Hyperplasia




Condition Overview

Pyometra is a life-threatening infection of the uterus that occurs most often in intact females over 6 years of age.


Signs of pyometra appear 1 - 2 months after the heat period. A dog with pyometra appears depressed and lethargic, may refuse to eat, drinks a great deal of water, and urinates frequently. Vomiting and diarrhea may also occur. The dogs temperature may be normal or even below normal.

There are 2 types of pyometra - open and closed. In open-cervix pyometra, the cervix relaxes and releases a large amount of pus tha often resembles tomato soup. These dogs usually do not appear as ill as those dealing with closed-cervix pyometra.

In closed-cervix pyometra, the undrained uterus enlarges, often producing a painful swelling in the lower abdomen. This type of pyometra is more likely to be accompanied by vomiting and diarrhea, and may produce signs of toxicity such as high fever, rapid pulse, and shock.


The disease often begins with a condition called cystic endometrial hyperplasia. in a dog with cystic endometrial hyperplasia, the inner glandular layer of the uterus becomes thickened, fills with fluid, and forms open pockets like those in swiss cheese. These endometrial changes are caused by the sustained effect of high levels of progesterone that occur during the 8 - 10 weeks of the 3rd phase of the heat cycle. Cystic endometrial hyperplasia provides ideal conditions for bacterial growth. The bacteria gain access to the uterus when the cervix is relaxed during estrus. The subsequent infection leads to pyometra.

Although estrogen does not cause cystic endometrial hyperplasia, it does increase the effects of progesterone. Estrogen given in the form of a mismate shot to prevent unwanted pregnancy has been associated with a greatly increased risk of pyometra and is no longer recommended for that purpose.


A biopsy may detect cystic endometrial hyperplasia, but the condition usually goes unnoticed until it has progressed to pyometra and the dog becomes ill.

Suspect pyometra in any un-spayed female who appears ill without obvious cause.

The diagnosis of closed-cervix pyometra is made by an X-ray of the abdomen showing an enlarged uterus. Ultrasonography distinguishes pyometra from the enlarged uterus of pregnancy - an X-ray taken after 45 days of pregnancy will also distinguish one from the other.


Pyometra requires immediate veterinary attention to prevent shock and death. Ovariohysterectomy, along with antibiotics, is the treatment of choice. It is best to do this operation before the dog becomes septic.

When it is important to preserve the reproductive potential of a valuable dog, an alternative to ovariohysterectomy can be considered - provided that the cervix is open and the dog is not septic.

This alternative treatment involves the use of antibiotics along with prostaglandin. Prostaglandin PGF2a (Lutalyse) relaxes the cervix, stimulates uterine contractions, and evacuates the pus. Lutalyse is administered y subcutaneous injection daily for 3 - 5 days. If evacuation is not complete, a second course is given. Antibiotics are selected based on sensitivity tests, and are continued for 1 - 3 weeks after evacuation of the uterus. Lutalyse is not licensed by the FDA for use in small animals, but is widely used for this purpose.

Prostaglandin treatment is accompanied by a number of dose-related side effects, including shock. Uterine rupture may occur when the cervix is closed. Most veterinarians regard closed-cervix pyometra as a contraindication to the use of Lutalyse.

Females who recover from pyometra are at increased risk for developing it again on subsequent heat cycles. The should be bred on the first estrus after recovery to maximize their chances for fertility.


Having your pet spayed will correct this issue.


Please contact your veterinarian with questions regarding this condition.

Show Sources & Contributors +


Dog Owners Home Veterinary Handbook

Publisher: Wiley Publishing, 2007

Website: http://www.wiley.com/WileyCDA/

Authors: Debra M. Eldredge, Liisa D. Carlson, Delbert G. Carlson, James M. Giffen MD

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