• Increased progesterone during diestrus promotes endometrial growth and glandular activity while suppressing myometrial activity. After multiple progesterone exposures (estrous cycles) the pathologic hyperplasia results in formation of cystic glands or Cystic Endometrial Hyperplasia (CEH). There is an increase in the number and size of endometrial glands, and inflammatory cell infiltrate. Hydrometra (fluid in the uterus) or mucometra (mucus in the uterus) eventually develop.

• Estrogen enhances the stimulatory effects of progesterone on the uterus by inducing progesterone receptors. In particular, pharmacological concentrations of estrogen administered during diestrus greatly increases the risk of pyometra.
• E. coli receptors may be induced and secondary bacterial infection results. The bacteria form an antigen - antibody complexes in the glomeruli. The endotoxins from bacterial infection causes decrease in specific gravity of urine (polyuria and polydypsia). There are different theories as to the exact mechanism, but Feldman and Nelson attribute it to either an interference of sodium and chloride resorbtion in the loop of Henle or an insensitivity to ADH

• Usually the dogs are greater than 6 years old, because it takes multiple progesterone exposures. This is a diestrus disease, so estrus was probably within the last month.
• With open cervix pyometra you see a vaginal discharge, lethargy, depression, anorexia/inappetance, polyuria/polydypsia, and vomiting. The dogs are generally relatively healthy though. WBC count is high or normal.
• With closed cervix pyometra you see depression, lethargy, weakness, inappetance, polyuria/polydypsia, and vomiting. The WBC is usually high with a left shift.

Sick

High white count

Polyuria/polydypsis

• White blood cell count is usually high with a left shift. UA may reveal isosthenuria.
• BUN may be elevated.
• Ultrasound and radiographs show an enlarged, fluid filled uterus. Ultrasound is particularly useful, as the normal pregnant uterus will show up as an enlarged uterus on radiographs.

• Ovariohysterectomy is the treatment of choice in the non-breeding bitch.

Lutalyse-the Upjohn-Pharmacia prostaglandin

• Prostaglandin plus antibiotics (broad spectrum to get the E. coli).  If it is a closed cervix pyometra, you should see some discharge by third day of treatment. Some people do not like to treat a closed cervix pyometra with prostaglandins as there is a fear of uterine rupture. There are reports of successful treatments of closed cervix pyometras (some died too!)
  • Relaxing the cervix has been done using Prostaglandin E, applied topically once or twice daily.
• Administer Lutalyse at a dose of 0.15 mg/kg, SC, BID or TID for 1-1½ days, then 0.25 mg/kg for 5-7 days. You may see all the side effects of prostaglandin such as restless, salivation, urination, vomiting, diarrhea, and cardiovascular collapse. These side effects are reduced if you begin with a low dose and increase the dose second day. The side effects usually diminish as treatment progresses.
• Reevaluate in 2 weeks. If any signs are still present, repeat the treatment.
• Breed the bitch on the next estrus as recurrence likely.
• Fertility has been reported after treatment, however it is lower than normal.

contributed by Bruce E Eilts and modified on 13 September 2005

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