Pyometra risk increases with each estrus cycle in intact female dogs, making older unspayed females at very high risk of a life-threatening emergency that could have been prevented.
Pyometra in older dogs creates an especially acute welfare challenge because the surgical risk is elevated in animals already experiencing systemic toxemia from uterine infection. Older dogs may have concurrent cardiac, renal, or hepatic disease that increases anesthetic risk just when emergency surgery is most urgently needed. This situation is entirely preventable through spaying at a younger, healthier age. The welfare argument for spaying extends beyond reproduction control to prevention of this common, life-threatening, and highly preventable disease.