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Surgical appearance of engorged uterine horns as a consequence of pyometra[1]

Pyometra, loosely defined as the presence of purulent material (pus) within the reproductive tract, is a common disease affecting almost 25% of all (unspayed) female dogs before 10 years of age[2].

The pathogenesis of canine pyometra is still unclear, but bacterial infection of the endometrium, mediated by bacterial lectins, is suspected to induce pyometra, especially during days 7 - 10 and 30 - 40 of dioestrus. Several other factors may also contribute, including genetic and hormonal factors. In dogs, the phagocytic ability of circulating leucocytes has been shown to decrease with age, and ovarian hormones have also been shown to affect immune resistance[3].

Causes include:

  • Undesexed females, often post-estral
  • Remnant uterus after desexing (uterine stump empyema)[4]
  • Bacterial
- Escherichia coli
- Streptococcus canis[5]
- Aspergillus spp

Clinical signs include anorexia, lethargy, purulent vulvar discharge, polyuria, polydipsia, proteinuria[8] and abdominal distention.

Diagnosis is usually based on clinical signs, physical examination, blood work, radiography, and ultrasonography, with confirmation through histopathologic evaluation of tissues.

A differential diagnosis would include uterine polyposis[9], pseudopregnancy and cystic endometrial hyperplasia[10].

Treatment usually requires overiohysterectomy, but lavage via direct trans-cervical catheterisation using a 5% povidone-iodine in saline solution has been successful in some cases where restoration of breeding is required[11].


  1. Vet Surgery Central
  2. Hagman R et al (2011) A breed-matched case-control study of potential risk-factors for canine pyometra. Theriogenology 75(7):1251-1257
  3. Holst BS et al (2013) Leucocyte phagocytosis during the luteal phase in bitches. Vet Immunol Immunopathol Feb 13
  4. Graves MR (2012) Pyometra in dogs and cats following ovariectomy. J Am Vet Med Assoc 240(5):513
  5. Kruger EF et al (2010) Relationship between clinical manifestations and pulsed-field gel profiles of Streptococcus canis isolates from dogs and cats. Vet Microbiol 146(1-2):167-171
  6. Tsioli VG et al (2011) Uterine leiomyosarcoma and pyometra in a dog. J Small Anim Pract 52(2):121-124
  7. Pettersson CH & Tidholm A (2009) Safety and efficacy of mid-term pregnancy termination using aglepristone in dogs. J Small Anim Pract 50(3):120-123
  8. Maddens B et al (2011) Evaluation of kidney injury in dogs with pyometra based on proteinuria, renal histomorphology, and urinary biomarkers. J Vet Intern Med 25(5):1075-1083
  9. Gumber S et al (2010) Uterine endometrial polyp with severe hemorrhage and cystic endometrial hyperplasia-pyometra complex in a dog. J Vet Diagn Invest 22(3):455-458
  10. Jankowski G et al (2012) Cystic endometrial hyperplasia and pyometra in three captive African hunting dogs (Lycaon pictus). J Zoo Wildl Med 43(1):95-100
  11. De Cramer KG (2010) Surgical uterine drainage and lavage as treatment for canine pyometra. J S Afr Vet Assoc 81(3):172-177