Cat Pyometra – Pyometra is an invisible, severe infection of the uterus that can be fatal to both dogs and cats when untreated. Infact cats and dogs can develop pyometra approximately 6-8 weeks after a heat cycle. The preferred method to treat pyometra is to perform an emergency spay and completely remove all the infection. The risk of pyometra is one of the many reasons we ALWAYS recommend you spay and neuter your pets.