What is Pyometra? Pyometra is a serious condition marked by inflammation of the uterus and the accumulation of pus . 🟢 Most Common in:  Intact female dogs over five years old (though it can occur in younger dogs). 🟢 Primary Cause:  Hormonal fluctuations during heat cycles. Understanding the Risks 🐾 Dogs typically experience two heat cycles per year , during which: ✅ White blood cell levels naturally decrease in the uterus to allow sperm passage—reducing infection defence.