Pyometra, which is made up of two latin words, 'pyo' meaning pus and 'metra' which is uterus, is an infection that affects older female dogs. The infection causes the uterus to distend with pus and abscesses, and complications arise as toxins bypass the uterine barrier as it is weakened and migrate around the body and spread infections.
In the absence of medical intervention, uterine tissue dies and may rupture and cause sepsis that can be fatal if not caught on time.
While the uterus itself is insulated from harmful bacteria, the vagina is not. Bacteria can travel up the canal and inflame the area.
After every heat cycle, the uterine wall thickens due to hormonal changes and in anticipation of pregnancy. Following each cycle the uterus tissue grows. This environment makes the area more susceptible to infection, which is why pyometra occurs most often in older females that are intact (not spayed).
Pyometra is a life-threatening condition and immediate veterinary care is required. Unfortunately, there is nothing you can do to help your dog at home since surgery is necessary in most cases.