Typical appearance of a dog with pyometra, exhibiting extreme lethargy

Pyometra is a life-threatening condition that occurs in mature unspayed female dogs and, less commonly, cats. It is an accumulation of purulent material within the uterus.

Pyometra usually occurs several weeks ( i.e. in cats 1 to 4 weeks and in dogs 4 to 8 weeks) after estrus or following mismating injections or exogenous administration of estrogens or progestins. The animal may present because of a purulent (pus-like), sometimes bloody vaginal discharge. Some animals may have obvious abdominal distension, fever, partial to complete anorexia, lethargy, fever, increased drinking and urination, vomiting, diarrhea and/or weight loss. Animals may present in septic shock, with a low body temperature and moribund if pyometra is not diagnosed early.

Pyometra can be open or closed - with an open pyometra there is an obvious vaginal discharge, and with a closed pyometra no discharge is present. Animals with a closed pyometra are usually much sicker, often with vomiting and diarrhea.

Lateral abdominal x-ray of a dog with pyometra. Note the enlarged uterus (arrows) in the caudoventral abdomen.

Pyometra can be diagnosed based on history, clinical signs, and a high index of suspicion by the clinician. Radiographs and/or ultrasound will confirm the diagnosis. Other possible diagnoses include mucometra, hydrometra, pregnancy, uterine torsion and peritonitis.

Surgery (ovariohysterectomy or spaying) is the recommended treatment. Surgery should not be delayed more than a few hours, especially in patients with a closed pyometra. Patients need to be stabilized prior to general anesthesia and surgery - this involves intravenous fluids for rehydration, intravenous antibiotics, treatment of electrolyte and acid-base abnormalities, and treatment of septic shock if necessary.

The prognosis following surgery is good if abdominal contamination is avoided, if shock and sepsis are controlled and if renal damage is reversed by fluid therapy and bacterial antigen elimination. The mortality rate even with appropriate therapy is 5 to 8%, and if the uterus has ruptured prior to surgery the mortality rate is higher (57% with uterine rupture).

Pyometra can be prevented by having your pet spayed.