Dog: Endometritis

General information

Other common/scientific names: chronic endometritis, cystic endometrial hyperplasia

Endometritis is defined as inflammation of the endometrium which is the lining of the uterus.

Diestrus is the period following a female’s heat cycle where she is no longer receptive to the male. During this stage, the female produces the hormone, progesterone, regardless of whether she is pregnant or not pregnant. Progesterone is the hormone which causes thickening of the lining of the uterus in preparation for pregnancy. Because of this fact, progesterone is considered inflammatory to the endometrium.


Endometritis in dogs is usually caused by a bacterial infection. The bacteria E. coli, Klebsiella spp, Staphylococcus spp and Streptococcus spp are commonly implicated.


If a dog has repeated heat cycles without becoming pregnant, the uterine lining continues to increase in thickness making it an ideal environment for the overgrowth of bacteria. With chronic endometritis, the lining can become cystic and secretes fluid which also aids in establishing an infection. Pyometra is a serious, often life-threatening consequence of endometritis. Other causes of an endometritis are a dystocia (difficult birth), retained fetuses, retained placenta and the use of progestational drugs.

Cardinal symptom

Vaginal discharge


Endometritis is characterized by a vaginal discharge occurring after a heat cycle. The discharge can be watery, bloody or purulent. The dog may lick her genital area.


Endometritis is diagnosed by history and physical examination. Ultrasonography of the abdomen may reveal an enlarged, thickened uterus. A vaginal swab may be obtained to evaluate cells under the microscope which indicate an infection.


The treatment of choice for endometritis is spaying.


If endometritis is diagnosed and treated before pyometra develops, the prognosis is excellent. However, pyometra can be life-threatening requiring emergency surgery.


Spaying the female dog will prevent endometritis.


It is important that all dog owners be aware of the risk of endometritis and pyometra if they leave their female dog intact or unspayed. Unspayed dogs should be observed closely at 8-10 weeks after the heat cycle for any signs of endometritis.

Update version: 4/24/2014, © Copyright by
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