Canis ISSN: 2398-2942


Synonym(s): Cystic endometrial hyperplasia with pyometra

Contributor(s): Lori Ludwig, Carlos Pinto


  • Disease of the luteal phase (metestrus - diestrus).
  • Cause: hormonally-mediated cystic endometrial hyperplasia associated with bacterial hemo-purulent metritis.
  • Signs: polydipsia/polyuria, vomiting, hemorrhagic-purulent vulvar discharge.
  • Diagnosis: signs, history, imaging (especially ultrasonography), exploratory laparotomy.
  • Treatment: ovariohysterectomy or conservative therapy with antibiotics and ecbolics if breeding potential is to be preserved.
  • Prognosis: good - if prompt treatment before animal systemically ill.
    Print off the owner factsheet Pyometra ('pyo' or womb infection) Pyometra ('pyo' or womb infection) to give to your client.



  • 5-6 estrous cycles → cyclic progesterone concentrations → marked proliferation and increased secretory function of the endometrium → cystic endometrial hyperplasia → pyometra.
  • Secondary bacterial infection of the material in the endometrial glands (embryotroph). 60-90% are due to E. coli Escherichia coliProteusspp Proteus spp and Klebsiellaspp Klebsiella pneumoniae. B-hemolytic streptococci are also important Streptococcus spp.

Predisposing factors

  • Older bitch (more than 6 years old); it may occur in young bitches following their first or second reproductive cycles.
  • 5-80 days after the end of estrus. >80% of bitches affected with closed pyometra still have a functional corpus luteum.


  • Use of estrogen for prevention of pregnancy (mismating).
  • Prolonged use of progestagens for the prevention or suppression of estrus.


  • 5-6 estrous cycles → progesterone-primed uterus → cystic endometrial hyperplasia → pyometra.
  • Renal disease: several aspects of the renal changes associated with pyometra are incompletely understood. In most dogs with E.coli pyometra, renal dysfunction is transient and it involves the nephron both at the glomerular and proximal tubular level. The renal dysfunction may be characterized by:

Prerenal uremia

  • Dehydration, shock and toxemia → poor renal perfusion → Ab-Ag complexes deposited on the basement membrane → glomerular disease → persistent proteinuria Proteinuria.
  • Bacterial toxins or immune complexes interfere with resorption → tubular disease → impaired ability to concentrate urine → polyuria → dehydration and electrolyte loss.
  • Concurrent renal disease is commonly found in older dogs.

Acid base balance

  • Metabolic acidosis Acid base imbalance is more common but metabolic alkalosis may develop through prolonged vomiting.


  • Vomiting, uterine loss and renal dysfunction → Na/K loss.

Bone marrow

White cells


  • 9-10 estrous cycles.
  • Metestrus (5-80 days after estrus).


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Verstegen J, Dhaliwal G, Verstegen-Onclin K (2008) Mucometra, cystic endometrial hyperplasia, and pyometra in the bitch: advances in treatment and assessment of future reproductive success. Theriogenology 70 (3), 364-374 PubMed.