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Pyometra is an infection of the uterus in dogs and cats causing a variety of clinical and pathological signs related to genital and systemic disease.  The uterus is generally filled with pus.  Although the disease has been recognized for decades, the true pathogenesis has still not been completely understood.  It is generally recognized that progesterone and estrogen and their receptors have a role in the development of pyometra; however, the infection is triggered by bacterial involvement. The cyclical hormonal influences of the female dog allow the uterus to go through changes that will be acceptable for fertilization of an embryo.  The changes that the uterus undergoes are typical for each dog. If bacteria are introduced into the uterus at a certain time during the cycle, hormonal regulation of the uterus allows the infection to start and become fulminate.

Signs and Symptoms

Because the infection can be so overwhelming, the reasons for presentation are not limited to the genital tract.  The animal can become so overwhelmed by the inflammation associated with the infection that the animal may die from its own uncontrolled inflammatory process. The most common clinical
signs that are present in >50% of dogs are:

  • LethargyDepression Anorexia
  • Excessive water intake   
  • Excessive urination  
  • Pale mucous membranes Vomiting    
  • Abdominal distension

Up to 16% of patients may have no clinical signs other than purulent vaginal discharge.

If your pet has recently had a heat cycle and displays any of the listed clinical signs, veterinary attention should be sought immediately. Most veterinarians are well equipped to diagnose a pyometra.  However, many patients will need 24 hour intensive care after the procedure to help with the systemic disease.

Exam, Screening Tests and Imaging

Most of the time, your veterinarian will probably suspect the diagnosis based on your history and the animal’s physical exam.  If the cervix is not open, the diagnosis may take a few more diagnostic tests. In general, a fluid distended uterus is needed to diagnose pyometra.  The veterinarian will most likely perform a general chemistry profile, complete blood count, urinalysis, abdominal radiographs, abdominal ultrasound and perhaps vaginal cytology to help rule in or out pyometra. Radiographs are typically very suggestive but abdominal ultrasounds will typically identify the fluid filled uterus
Surgery is almost ALWAYS indicated with Pyometra.