Pyometra is one of the most common, serious, and worrisome disorders in the bitch. It is a hormonally mediated disorder of diestrus, which means that the disease is invariably associated with the progesterone-dominated phase of the ovarian cycle. The disease results from over-whelming bacterial growth within the uterus. The infection causes a mild to severe, potentially life-threatening septicemia (presence of bacteria in the bloodstream, accompanied by related clinical signs of disease) and toxemia (presence of toxins in the blood, accompanied by clinical signs), which require aggressive therapy. The uterus may have undergone pathologic changes prior to development of the disease, which is assumed to be caused by an exaggerated response to progesterone stimulation. It is extremely rare for pyometra to occur in a bitch that is not under the influence of progesterone.
The Older Bitch
Bitches older than 7 to 8 years of age are increasingly prone to the development of pyometra. The syndrome is the result of repeated exposures to progesterone during normal diestrus phases. After years of cyclic ovarian activity, the predisposition for and incidence of pyometra increase. The risk of developing pyometra thus becomes exaggerated in an othÂ¬erwise healthy older dog.
The Younger Bitch
A significant number of young bitches (6 months to 6 years of age) have been diagnosed with pyometra. It is unlikely that the same process seen in older dogs would account for their uterine disease. However, there is a strong correlation between the incidence of pyometra in young dogs and estrogen administration, given in an attempt to prevent pregnancy. Estrogen administration for accidental breedings is not recommended (see “MISMATING,” above). If the misbred bitch is not valuable as a brood bitch, she should be spayed. If she is of value, an unwanted pregÂ¬nancy or induced abortion is far preferable to the side effects of estrogen therapy.
History and Clinical Signs
Clinical signs will depend upon the patency of the cervix. An obvious sign seen in bitches with an open-cervix pyometra is a vaginal discharge which looks and smells like pus. The discharge is usually first noticed 4 to 8 weeks after standing heat. Pyometra has been diagnosed as early as the end of standing heat and as late as 12 to 14 weeks after standing heat. Other common signs include lethargy, depression, lack of appetite, increase in water intake and urine output, vomiting and diarrhea. The overall health of the affected dog is most dependent on how quickly the owner recognizes the problem and seeks veterinary assistance.
The bitch with closed-cervix pyometra is more often quite ill at the time of diagnosis due to the lack of an obvious and easily recognized vaginal discharge as is seen in open-cervix infection. Instead, owners notice an insidious onset of signs that usually include depression and inappetence. In conjunction with the vomiting and diarrhea associated with this syndrome, dogs with closed-cervix pyometra may become critically ill or even die.
Diagnosis and Complications
Pyometra can often be diagnosed rather easily. A diagnosis of pyometra should be suspected in any ill bitch. The diagnosis is confirmed when the appropriate clinical signs are present in conjunction with typical abnormalities on physical examination, laboratory studies, and X-ray or ultrasonographic evaluation. A definitive diagnosis becomes a challenge when the history is vague (especially regarding ovarian cycle activity) or when a vaginal discharge is not present (closed-cervix pyometra).
Spaying is the preferred treatment for pyometra unless the owner strongly wishes to maintain the reproductive potential of the affected dog. Relatively healthy bitches are usually excellent surgical risks; severely ill animals should receive intensive care. In some dogs surgery should not be postponed for more than a few hours.
Medical therapy utilizing hormones and quinine produces inconsistent results and is not often successful. In addition, systemic antibiotics are usually ineffective as the sole therapy for canine pyometra. However, results using prostaglandins have been extremely encouraging, and these compounds now offer a reliable medical alternative for therapy. The medication causes contraction of the uterus, reduction in circulating progÂ¬esterone concentrations, and (the least consistent effect) relaxation of the cervix. This therapy as used by an experienced veterinarian can be extremely effective.