TEXTBOOK OF VETERINARY INTERNAL MEDICINE
Client Information Series; written by Dr Autumn P. Davidson
Pyometra is a progesterone-mediated uterine disorder in bitches and queens.
Progesterone is the female hormone that works to maintain pregnancy. All normal female dogs are naturally exposed to tremendous concentrations of progesterone during the 45 to 75 days that follow the period of breeding (the period called diestrus).
Progesterone places the nonpregnant uterus at risk for bacterial infection.
These bacteria are normally found in the vagina but have infected the uterus by migrating through the cervix.
A bacterium called Escherichia coli is the most common cause of pyometra in both bitches and queens.
The incidence of pyometra is thought to be greater in the bitch than the queen because dogs are exposed to natural progesterone more frequently than cats. An increased incidence of pyometra is associated with estrogen administration in the bitch.
Therefore, estrogen should not be used as a treatment for "mismate" in dogs.
Administration of progesterone to queens can also precipitate pyometra.
Progesterone compounds should not be used as anti-inflammatory or behavior-modifying drugs in intact queens.
Pyometra can occur with or without vaginal discharge, depending on the ability of uterine contents to flow through an open (patent) or closed cervix. Closed cervix pyometra is more serious because some of these dogs become ill before an owner realizes there is a problem.
In contrast, dogs with "open cervix" pyometra can be recognized as having a problem earlier because they usually have an obvious, malodorous, pus-colored vaginal discharge before they become seriously ill.
Dogs with closed cervix pyometra may suffer from uterine rupture, which can be as critical and life threat-ening as when people have a ruptured appendix. In addition to the vaginal discharge, the classic clinical signs of pyometra include partial to complete loss of appetite, fever, lethargy, weight loss, an unkempt appearance, vomiting and diarrhea, and excessive thirst and urination.
Blood and urine tests are consistent with infection and may indicate involvement of other organs that can be harmed by this severe disease. Abdominal x-rays and ultrasonography can be useful in confirming the diagnosis. Although it is rare, pyometra can occur in one uterine horn with pregnancy in the other.
The best, least expensive, most reliable, quickest, and easiest treatment for pyometra, after stabilization of your dog or cat with intravenous fluids and antibiotics, is the spay (ovariohysterectomy). This would not be the first and best treatment only if your pet is younger than 6 years of age and a valuable breeding bitch or queen.
Medical treatment of open cervix pyometra, using prostaglandin F2c. (PGF2cy) and appropriate antibiotics, has been successful in both the bitch and queen. Antibiotics alone are almost never successful in completely resolving pyometra.
PGF2 causes emptying of uterine contents and a lowering of blood progesterone levels. The presence of live fetuses should be ruled out by use of ultrasonography before treatment because the drug causes abortion and because the treatment is not usually successful if there are any remnants of previous pregnancies in the uterus. Those dogs and cats should be spayed, as should any dog or cat that is extremely ill. The PGF2c. treatment should never be used for an extremely ill dog or cat.
Bitches and queens may need to be hospitalized for the PGF2~ treatment to enable administration of adjunct supportive care, such as intravenous fluids and antibiotics, and to permit monitoring of adverse effects and outcome of treatment. The treatment protocol includes 5 to 7 days of injections. Most can be treated on an outpatient basis because dogs and cats treated with PGF2~ should never be critically ill.
Predictable physical reactions that occur after the administration of this drug include restlessness, panting, salivation, vomiting, diarrhea, urination, and dilatation of the pupils (bitch and queen) and grooming, lordosis, and kneading (queens). These reactions usually resolve within 5 to 60 minutes. After each subsequent injection, the reactions diminish in severity and duration. Reactions are rarely considered severe enough to warrant discontinuation of the drug.
A successful short term response, defined as resolution of the signs of pyometra, may not be evident at the completion of PGF2(~ treatment. At the time of release from the hospital, bitches and queens should have an improved appetite and normal rectal temperature. However, the abnormal vaginal discharge may be completely gone or may persist for another 5 to 10 days.
Reexaminations should be scheduled for 7 and 14 days after completion of treatment. At 2 weeks after treatment, there should be little or no vaginal discharge and the pet should be otherwise healthy. Abdominal x-rays or ultrasonography can be used to evaluate reduction in uterine size compared with that on previous examinations.
Persistence of problems suggests that retreatment be considered. A second series of injections for recurrent pyometra can be successful and may be considered if the condition of the bitch or queen permits. A successful long-term response is defined as a return to normal estrous cycles and, if bred, conception and carrying a litter to term. Breeding at the next estrus is recommended to avoid potential complications after progesterone's effects on a nonpregnant uterus. Prostaglandins do not resolve underlying uterine wall disease. The overall successful conception rate after PGF2L. treatment has been reported to be 40 to 82 per cent in bitches and 85 per cent in queens.