Pyometra in Cats: Deep Welfare Guide
Disease Overview
Pyometra (pus in the uterus) is a life-threatening bacterial infection of the uterus, most common in entire (unspayed) queens over 5 years old. It develops under progesterone stimulation following oestrus. In open pyometra, the cervix remains open allowing discharge; in closed pyometra, the cervix is closed, causing rapid uterine distension and systemic toxaemia. Closed pyometra is more acutely life-threatening due to absence of drainage.
Welfare Consequences
Pyometra causes significant suffering: fever, lethargy, anorexia, polydipsia/polyuria, abdominal distension (visible in open pyometra), and vaginal discharge. Endotoxaemia causes systemic illness, dehydration, and cardiovascular compromise. Uterine rupture causes peritonitis (catastrophically painful and rapidly fatal). Renal failure develops as a consequence of bacterial toxin-induced kidney damage. The combination of infection, pain, and systemic illness causes severe acute welfare harm.
Diagnosis
Diagnosis is based on history (entire female, middle-aged/older, recently in oestrus), clinical signs, blood tests (elevated white blood cells, elevated kidney values, elevated ALP), and abdominal imaging. Ultrasound is the gold standard, demonstrating uterine distension filled with fluid. Open pyometra is easier to diagnose due to purulent vaginal discharge; closed pyometra may mimic other causes of acute illness.
Emergency Surgical Treatment
Ovariohysterectomy (OVH, spay) is the definitive treatment: removal of the infected uterus and ovaries resolves the infection and prevents recurrence. Emergency surgery is performed after initial stabilisation (IV fluids, antibiotics). Surgery is higher risk than routine OVH due to the patient's compromised condition, but delay worsens outcome. Recovery is typically rapid after successful OVH.
Medical Treatment and Prevention
Medical management with prostaglandins (to open the cervix and promote uterine drainage) can be attempted in open pyometra in cats intended for future breeding, but success rates are lower than in dogs, recurrence is common (up to 70% in subsequent cycles), and the welfare risk of recurrence is significant. Neutering (OVH) of non-breeding queens before the development of pyometra is the most effective prevention. Every entire queen that is not being used for breeding is at risk; routine neutering from 4-6 months eliminates this risk entirely.