Pyometra in the Bitch by Janice Selinger, DVM The following article is by Janice and was first published in the "Ontario Toller" .
Pyometra means an accumulation of pus in the uterus (Greek, "pyo" = pus, "metra" = uterus). It is a very serious disease, not uncommon in older unspayed bitches, and can result in death. Pyometra is the final stage of a process of uterine disease. Bitches ovaries normally produce the hormone progesterone after estrus to prepare the uterus for pregnancy. The lining of the uterus thickens, and glands develop to release nutrients to nourish the early embryo until the placenta develops. The normal uterine defense mechanisms are also supressed to prevent them from attacking the newly implanted embryos. These changes take place whether the bitch is pregnant or not. Some bitches, however, seem to be unusually sensitive to the effects of progesterone. The uterine lining thickens excessively, and the glands develop abnormally, sometimes forming cysts, and release so much secretions that fluid may accumulate inside the uterus. This process progresses with each non-pregnant cycle that the bitch has. The fluid secretions encourage the growth of bacteria, particularly since uterine defenses are inhibited. Now there is inflammation of the uterine lining, known as "endometritis." There are usually no clinical signs, except that the bitch is more likely to be infertile. If the infection becomes severe enough, pus forms in the uterus, and now the bitch has pyometra.
Pyometra is most common in older and middle-aged bitches. There do not appear to be any breed-related or genetic relationships. Typically, the bitch has not had a litter. She has either never been bred or has a history of being bred unsuccessfully (infertility). Multiple non-pregnant estrous cycles are associated with the changes that result in pyometra. However, young bitches may also get pyometra, particularly if they have been given a large dose of estrogen (a "morning-after" shot to prevent pregnancy in cases of accidental mismating). Estrogen increases the sensitivity of the uterine lining to progesterone. Pyometra most commonly occurs 4 to 8 weeks after standing heat, but can occur as early as the end of heat or as late as 12 weeks after heat.
The clinical signs of pyometra include lethargy, depression, loss of appetite, increased drinking of water and increased urination, and possibly vomiting. If the cervix is open and the uterus is draining ("open pyometra") there will be a discharge from the vagina of pus and/or blood. About 15% of the time the cervix is closed ("closed pyometra") and there is no discharge. The severity of signs varies. Some bitches with open pyometra may be relatively healthy except for the abnormal vaginal discharge. A diagnosis of pyometra is made on the basis of physical exam, history, blood and urine tests, and radiography. Blood tests will usually show an elevated white blood cell count in response to the infection. Occasionally,
the white blood cell count may be normal, possibly because the white blood cells are sequestered in the uterus. There may be changes in the urine if toxins released by the bacteria affect the kidneys. This is also what causes increased drinking and urination. Radiographs (X-rays) may reveal the presence of an abnormal enlarged fluid-filled uterus in a bitch that is not pregnant or in early pregnancy. In mid-pregnancy, it is not too easy to distinguish between a uterus filled with pus and a uterus filled with pups. Only in very late pregnancy do the puppies' bones become calcified enough to show up on an X-ray. Ultrasound is a much better diagnostic tool. It can determine the presence of pyometra at any stage of pregnancy. In some cases, swabbing the vagina and making a smear to look for white blood cells or culturing for bacteria may be helpful.
The preferred treatment is always to spay the bitch. She may need emergency care, intravenous fluids, and antibiotics to stabilize her before surgery can be performed. If toxins from the bacteria are causing septicemia, only surgical removal of the infected uterus can resolve the septic condition.
If the bitch is a valuable breeding animal and is not too ill, medical treatment may be possible. Injection with the naturally occurring hormone prostaglandin F2alpha (PGF2a) is often successful in treating pyometra. Prostaglandin works by causing the uterus to contract and expel the pus, and by decreasing the production of progesterone. Side effects may include restlessness, abdominal cramps, drooling, panting, and maybe diarrhea or vomiting. Antibiotics are used for several weeks as follow up therapy. Bitches with closed pyometra do have a risk of rupturing the uterus and spreading the infection. Following such treatment, the bitch must be bred on her next estrous cycle, or the pyometra will likely recur. She should receive antibiotics during proestrus and estrus, and her white blood cell count should be monitored after breeding. Early pregnancy should be confirmed by ultrasound to differentiate from pyometra. It may be wise to establish the number of puppies desired from this dam and breed her on her next few consecutive cycles, get two or three litters from her, and then spay her. If she is a young bitch with pyometra due to a cause such as estrogen treatment, it may not be necessary to breed her on every heat. She should be carefully monitored however.
The likelihood of a bitch returning to reproductive capacity after pyometra varies. If she was never successfully bred before, she probably still won't get pregnant. If she has previously whelped and is in good health, chances are 50 to 75% that she will be able to bear another litter. Her fertility may be reduced due to damage to the uterus caused by the pyometra. If there is uterine scarring, there are fewer locations for the new embryos to implant, and litter size will be smaller. As well, remember that pyometra mainly affects older bitches, at a time when their fertility is naturally declining anyway.