Pyometra in the Bitch



  • Cystic Endometrial Hyperplasia (CEH) vs Pyometra
    • Two distinct entities
    • CEH
      • From repeated repeated progesterone exposure (cycles)
      • Glands vary in size
      • Glands cystic
      • Sterile fluid - mucometra or hydrometra
      • Not an inflammatory condition
      • Increased progesterone and estrogen receptors
      • Can induce CEH with:
        • Mechanical irritation
        • Biopsy
        • Scarification
        • Silk suture
        • Bacteria
        • Changes reverse if progesterone removed
      • Another form of endometrial hyperplasia
        • As with CEH, it occurs primarily during the luteal phase of the cycle,
        • Endometrium responds to stimuli with a highly organized proliferative remodeling (similar to the normal histology of the endometrium at placentation sites in normal pregnancy)
        • . Although referred to as deciduoma, Schlafer and Gifford propose the use of the term pseudo-placentational endometrial hyperplasia to help distinguish it from CEH
    • Pyometra
      • Complex etiology
        • Hormone
        • Infectious
        • Immunologic
      • Hormone
        • Estrogen and Progesterone not different in pyometra vs. normal cycle
        • Receptors normal (one study found reduced)
        • 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.
          • Recent study showed no difference when estradiol benzoate was used for mismate.
        • Bacterial
          • E. coli.
            • Primary
            • 11-20 and 21-30 days post LH primary days of infection
            • Same as intestinal or urinary tract
              • Same virulence factors
              • P fimbriae - enhances tissue damage
              • α-haemolysin- enhances free iron
              • Cytotoxic necrotizing factor 1 -  enhances tissue damage
            • Endotoxin release
              • lipopolysaccharide parts of the cell wall of gram-negative bacteria - thought to be responsible for the systemic signs of pyometra in bitches
              • Stimulates prostaglandin synthesis (especially PGE2), which further contributes to the suppressed activity of cellular immunity during diestrus.
                • Measuring  blood concentration of the PGF metabolite (PGFM) also provides an indicator of endotoxin release in bitches with pyometra, and helps in the differentiation between pyometra and CEH
            • Other bacteria
              • Streptococcus spp,
              • Klebsiella species,
              • Staphylococcus aureus,
              • Pasteurella spp,
              • Proteus spp
              • Pseudomonas spp
            • Systemic inflammatory response syndrome (SIRS)
              • Uncontrolled production of other inflammatory mediators
                • tumor necrosis factor (TNF)
                • interleukins (IL-1 and IL-6)
                • platelet activating factor
                •  may provoke irreversible damage to internal organs or septic shock, which can cause death
            • Polyuria/polydypsia
              • Multifactorial origin
              • Renal tubular cell damage,
              • Impaired ability of the loop of Henle to reabsorb sodium and chloride,
              • Increased tubular insensitivity to anti-diuretic hormone (ADH)
              • Loss of urinary concentrating ability.
              •  Not an immunomediated glumerulonephritis.
              • No glomerular damage
              • Reversible after OHE and is most likely due to endotoxin effects




Clinical signs
  • May be none with uncomplicated CEH or mucometra or hydrometra
  • 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.


High white count


  • History
  • Clinical signs
  • White blood cell count is usually high (30,000) with a left shift.
  • UA
    • May reveal isosthenuria.
    • Do not do cystocentisis
  • 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.
    • 5 to 8% mortality
    • Systemic antibiotics for 2 weeks

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 (misoprostol), applied topically once or twice daily.
    • Administer Lutalyse at a dose of 0.15 mg/kg, SC, BID or TID for 1-1 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.
  • Prostaglandin with a dopamine-agonist or a progesterone-receptor antagonist
    • Clinical improvement in 48 hours
    • No discharge in 4-7 days
    • Normal CBC in 6-15 days
  • Dopamine agonists (cabergoline 5 g/kg once a day or bromocriptine 25 g/kg, twice or thrice daily) with either natural or synthetic prostaglandins.
    •  Potentiates the luteolytic effects of each drug resulting in a more rapid luteolyses
    • Allows using lower PG doses
    • Progesterone concentrations decline in <24 to 48 hours,
    • Cervical opening  1-2 days,
    • Success rate
      • 80% with the combination of cabergoline (5 g/kg PO) and cloprostenol (1 g/kg SC) once a day for 7 days. Cloprostenol administration was continued until day 14, if no response to treatment was observed.
      • 95% - cabergoline (5 g/kg PO) and cloprostenol (5 g/kg) administered every third day, during 10 days.
    • Progesterone-receptor antagonists {mifepristone (RU 486) or aglepristone (RU 534)}
      • Competitive antagonists of the progesterone receptor - result in decreased intra-uterine progesterone
      • Prevents progesterone effects
      • Causes cervical relaxation - Aglepristone can be used as an effective means of inducing cervical dilation in cases of closed cervix pyometra (within 48 h)
      • Should be used in combination with prostaglandin
      • Combination of aglepristone (10 mg/kg on days 1, 2 and 8) with cloprostenol (1g/kg on days 3-7)
        • More effective than aglepristone alone
        • Success rate at day 90 of 84%
        • Clinical signs, blood parameters and uterine diameter consistently improved to normal values,
  • Breed the bitch on the next estrus as recurrence likely.
  • Fertility (64-87%) has been reported after treatment, however it is lower than normal.

contributed by Bruce E Eilts and modified on23 September 2009

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contributed by Bruce E Eilts on 25 September 2012


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