Pyometra

Two forms of pyometra exist — open and closed — and they present somewhat differently:

• Open pyometra (cervix open) — pus drains from the vagina, producing a visible bloody, creamy, or brown-green discharge. The drainage may be mistaken for a normal heat cycle, delaying recognition
• Closed pyometra (cervix closed) — pus has no outlet and accumulates inside the uterus. The abdomen may visibly distend. This form is more dangerous because toxins build up faster and systemic signs progress rapidly

Common signs across both forms include:

• Increased thirst and urination (polydipsia/polyuria) — toxins from the infection impair kidney concentrating ability
• Lethargy, weakness, or collapse
• Decreased appetite or complete refusal to eat
• Vomiting and/or diarrhea
• Abdominal distension or obvious discomfort when the abdomen is touched
• Vaginal discharge (absent in closed pyometra)
• Fever — though some severely septic patients have normal or even low body temperature
• Pale, gray, or tacky gum color — a sign of shock requiring immediate emergency care

Pyometra develops when bacterial colonization of the uterus occurs during or after the influence of progesterone on the uterine lining. Several factors set the stage:

• Intact (unspayed) female status — pyometra does not occur in spayed females; ovariohysterectomy before the first or second heat cycle essentially eliminates lifetime risk
• Progesterone exposure — after each heat cycle, progesterone prepares the uterus for pregnancy by thickening the lining and suppressing the local immune response. Repeated cycles without pregnancy cause progressive cystic changes (cystic endometrial hyperplasia) that create the ideal environment for bacterial growth
• Age — middle-aged to older females are most commonly affected, though younger animals can develop pyometra. The average affected dog in published studies is around eight years old, but cases in animals as young as one to two years are documented
• Exogenous progesterone or estrogen — injected or oral hormones used to suppress or manipulate heat cycles significantly increase pyometra risk and should be avoided in unspayed females intended for later breeding
• Cats — pyometra is less common than in dogs but does occur; the same principles apply. Queens (intact female cats) that cycle frequently without becoming pregnant accumulate hormonal uterine changes over time

In any ill, intact female presenting four to eight weeks after a heat cycle, pyometra is high on the diagnostic list. The workup confirms the diagnosis and establishes how critically ill the patient is:

• Abdominal ultrasound — the fastest and most reliable way to confirm a fluid-filled, enlarged uterus and estimate the severity of distension
• Complete blood count — typically shows a markedly elevated white blood cell count; severely septic cases may paradoxically show a low WBC (bone marrow exhaustion)
• Blood chemistry and electrolytes — kidney function parameters, protein levels, and liver values assess organ damage from sepsis and guide fluid resuscitation
• Abdominal radiographs — can reveal a markedly enlarged tubular structure in the abdomen, especially in closed pyometra with significant uterine distension
• Urinalysis — kidney toxin-induced changes are common; the team distinguishes pyometra-related kidney impairment from primary kidney disease

Speed matters: once pyometra is confirmed, surgery is planned the same day in nearly all cases.

Emergency ovariohysterectomy — surgical removal of the infected uterus and ovaries — is the treatment of choice for pyometra and is curative. Pre-operative stabilization with intravenous fluids, antibiotics, and supportive care begins immediately upon admission:

• Surgical stabilization and emergency OHE — IV fluids correct dehydration and support blood pressure; broad-spectrum antibiotics are started pre-operatively and continued post-operatively. The surgical procedure removes the infected uterus intact (preventing spillage of pus into the abdomen), along with both ovaries, preventing recurrence
• Post-operative intensive care — continued IV fluids, antibiotics, anti-nausea medication, and pain management. Kidney function is closely monitored; some patients require extended support while the kidneys recover from the infection
• Medical management (rare, specific cases only) — prostaglandin therapy and antibiotics can be considered in young, valuable breeding animals with open pyometra who are not severely ill. This is not curative for cystic endometrial hyperplasia, and recurrence rates are high. It is not appropriate for closed pyometra, severely ill patients, or pets not intended for breeding

The vast majority of dogs and cats treated promptly with surgery make a full recovery. Delayed treatment dramatically increases mortality risk.

Pyometra moves fast. Any intact female that is drinking more than usual, seems lethargic, has lost her appetite, or has unusual vaginal discharge — especially if she had a heat cycle in the past two months — needs same-day veterinary evaluation. Do not wait overnight to see if she improves. If gums are pale or gray, or if the pet is weak or collapsed, go directly to an emergency clinic without delay. After emergency stabilization, our team at Dog & Cat Hospital Calabasas can manage ongoing post-operative care and recovery. The single best prevention is spaying female dogs and cats before their first or second heat cycle — a conversation worth having at any wellness visit. Book an appointment to discuss spaying or to have a symptomatic pet evaluated today.