The general characteristics of pyometra
Keywords: pyometra, mare, equine
A mare with pyometra discharging pus from her vulva. Note the copious amounts of pus on the floor (arrow). Pyometra is easily appreciated by transrectal ultrasonography (inset).
Image size: 1800 x 1321px
Pyometra in mares is unlike the condition in cows. It is not usually a postpartum phenomenon and does not invariably block estrous cycles as it does in cows. Pyometra is often an incidental finding in mares unless there is a purulent discharge as occurred here. It is usually due to infection with Streptococcus. zooepidemicus.
Affected mares (and cows) are not usually systemically ill like bitches and queens; not even the hemogram is significantly affected. Contrary to what is occasionally stated, the cervix does not have to be abnormal for mares to develop pyometra.
Like cows, mares are treated with prostaglandin if a corpus luteum is present, but unlike cows, the cornerstone of treatment involves physical drainage of the uterus, not prostaglandin treatment on its own.
During treatment, the cervix is dilated manually and a sterile stomach tube or stallion catheter inserted. Saline is admitted to the uterus to start a siphon and the pus is then drained. Volumes of pus are variable but can be great. This bucket in this image was one of two drained from this mare. The uterus is flushed with saline after it has been drained and about 10 million IU of penicillin (sodium or potassium) in ~100 ml of saline are left in the uterus. Systemic antibiotics are not usually required.
| Unfortunately the condition usually re-occurs; some mares requiring physical drainage every two or three months. The prognosis for complete resolution of pyometra is usually dismal. |
Hysterectomy is not a common form of treatment because of its surgical difficulty in mares.
Although there is little evidence to support such a statement, it is thought that failure to drain pus on a regular basis may predispose mares to uterine rupture.
