ISSN 2398-2950      



Synonym(s): Cystic endometrial hyperplasia


  • Disease of the luteal phase.
  • Hormonally mediated cystic hyperplastic endometritis associated with a bacterial infection.



  • Secondary bacterial infection of the material in the endometrial glands (embryotroph) may include Escherichia coli  Escherichia coliProteus spp, B-hemolytic streptococci  Streptococcus spp and occasionally anaerobes.

Predisposing factors


  • Middle to old age.
  • Successive luteal phases without pregnancy.


  • Prolonged use of progestagens for the prevention or suppression of estrus.


  • Successive luteal phases without pregnancy, ie following non-fertile mating-induced ovulation or occasionally spontaneous ovulation (pseudopregnancy Pseudopregnancy), or progestagen use   →   repeated and prolonged progesterone concentrations   →   cystic endometrial hyperplasia   →   pyometra.
  • Renal disease: several aspects of the renal changes associated with pyometra are incompletely understood but some suggestions include:

Prerenal uremia

  • Dehydration, shock and toxemia   →   poor renal perfusion   →   Antibody / Antigen (Ab-Ag) complexes deposited on the basement membrane of the glomerular apparatus   →   glomerular disease   →   persistent proteinuria.
  • Bacterial toxins or immune complexes interfere with Na+ resorption from the distal convoluted tubule and collection ducts   →   tubular disease   →   impaired ability to concentrate urine   →   polyuria   →   dehydration and electrolyte loss.
  • Concurrent renal disease may be found in older cats.

Acid base balance

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


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

White cells


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Tobias K M & Wheaton L G (1995) Surgical management of pyometra in dogs and cats. Semin Vet Med Surg (Small Anim) 10 (1), 30-34 PubMed.
  • Davidson A P, Feldman E C, Nelson R W (1992) Treatment of pyometra in cats, using prostaglandin F2 alpha - 21 cases (1982-1990). JAVMA 200 (6), 825-828 PubMed.
  • Potter K, Hancock D H, Gallina A M (1991) Clinical and pathologic features of endometrial hyperplasia, pyometra, and endometritis in cats - 79 cases (1980-1985). JAVMA 198 (8), 1427-1431 PubMed.
  • Marretta S M, Matthiesen D T, Nichols R (1989) Pyometra and its complications. Probl Vet Med (1), 50-62 PubMed.
  • Schulman J & Levine S H (1989) Pyometra involving uterus masculinus in a cat. JAVMA 194 (5), 690-691 PubMed.
  • Kenney K J, Matthiesen D T, Brown N O et al (1987) Pyometra in cats - 183 cases (1979-1984). JAVMA 191 (9), 1130-1132 PubMed.
  • Arnbjerg J & Flagstad A (1985) Prostglandin F2 alpha treatment of feline open pyometra. Nord Vet Med 37 (5), 286-290 PubMed.
  • Gillespie D & Kock N (1983) Pyometra in a Pallas's cat. JAVMA 183 (11), 1322-1323 PubMed.
  • Wiessing J & Thomson K S (1980) Treatment of feline pyometra with dinoprost. N Z Vet J 28 (6), 112 PubMed.

Other sources of information

  • Chandler E A, Gaskell C J & Gaskell R M (1994) Feline Medicine and Therapeutics. 2nd edn. Oxford: Blackwell Scientific Publications, pp 272-273. ISBN 0 632 03361 4.
  • Christiansen I J (1984) Reproduction in the Dog and Cat. London: Bailliere Tindall, pp 243-245. ISBN 0 7020 0918 0.

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