Pyometra means that the womb becomes infected and fills with inflammatory content. The disease is seen mainly in unspayed female dogs in the weeks after a season. The dog may become tired, eat less, vomit, get a fever and start drinking and peeing more. If the cervix is open, a discharge may be visible, but with closed pyometra there may be no discharge at all.
Because the symptoms sometimes start quite discreetly, the time since the last season is important information. The diagnosis is based on an examination and is often supported by blood tests and ultrasound or other imaging. Surgery to remove the womb and ovaries is a common treatment, together with stabilising care as needed.
Contact a vet urgently if an unspayed female dog becomes ill after a season, especially with increased thirst, reduced appetite, vomiting or discharge. Do not wait for all the classic symptoms to appear, as closed pyometra may have no visible discharge.