Pyometra
Basic Information 
Epidemiology
Risk Factors
• Any condition that causes cervical closure and physically impedes uterine drainage.
• Although not always a factor, it is well-accepted that previous significant trauma to the cervix (eg, during foaling) that creates fibrous tissue and causes cervical adhesions may result in subsequent closure of the cervix and development of pyometra.
• Other causes of cervical closure include progestin therapy or creation of a tortuous cervical canal caused by the presence of neoplasia. Chronic infection with fungal organisms and Pseudomonas aeruginosa infection have also been implicated.
Clinical Presentation
Etiology and Pathophysiology
• Previous cervical trauma, such as a tear during foaling, predisposes mares to cervical adhesions.
• Cervical adhesions may cause the cervix to seal and lead to fluid accumulation within the uterine lumen. If infection is present at the time of cervical closure, this fluid becomes purulent and continues to accumulate with no opportunity for outflow.
• Alternatively, mares with residual endometritis that are inadvertently given progestin therapy (eg, altrenogest, progesterone) are at risk for developing a prolonged endometritis because of cervical closure and may develop pyometra over time.
Diagnosis 
Differential Diagnosis
• Contagious equine metritis (CEM)
• It is important to differentiate this disease from CEM. Mares with CEM typically present with copious mucopurulent discharge from the reproductive tract and have a history that includes breeding within the past 14 days. Although the presentation of these two conditions is very different, CEM should be mentioned here as a cause of purulent discharge from the reproductive tract because it is a reportable disease of great significance to the equine industry (see “Contagious Equine Metritis” in this section).
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