One of the most serious conditions affecting the female dog is a chronic infection of the uterus called pyometra. In this condition, the uterus becomes filled with a purulent material which builds up gradually and which eventually causes generalized toxic effects threatening the life of the dog.
Pyometra in dogs is usually seen in females above 8 years of age and is more common in bitches that have not had puppies. The first signs of the illness are not definite, and as the changes in the dog’s behavior are gradual, they are often put down to advancing age.
The dog at first becomes less active, is more inclined to sleep and may gradually lose weight despite eating normally. When the dog comes into season, the duration of bleeding may be more prolonged and the discharge may be lighter in color than normal and have an offensive smell. The dog may start to refuse food and may vomit occasionally. It is at this point that the owner usually seeks help.
The more serious form of the disease occurs when the cervix does not open and allow the release of the tell-tale purulent discharge. These cases are very difficult to detect in the early stages, as the dog merely appears to be lacking energy.
It may begin to drink more water than usual as the toxic wastes absorbed from the uterus begin to affect the cells in the kidney. Occasional vomiting occurs and the dog loses weight.
If the condition still goes undetected the dog may suddenly collapse. At this point, it is very difficult to reverse the well-established toxic effects on the liver and kidney cells.
The infection of the uterus can occur in younger dogs. The prolonged administration of hormones to postpone the normal heat periods in the bitch make the dog more liable to infection. The administration of these hormones to the immature dog dramatically increases the likelihood of infection.
Under the influence of high levels of progesterone, the cells lining the uterus secrete a thin mucus discharge. The presence of this mucus provides an ideal medium for the growth of any bacteria present.
Where normal seasons exist there is a natural cleansing effect at each heat period. At this time the blood supply to the cells of the uterus is increased and the cervix opens to allow the accumulated debris to be swept out of the uterus.
Where the luteal phase of the ovary is prolonged, as happens in older animals or in bitches given artificial progesterone, the cleansing effect of estrous does not occur and the accumulations of mucus bacterial cells and white blood cells build up to such a degree that the uterus may become so enlarged that it fills most of the abdominal cavity.
The only effective treatment for pyometra is the surgical removal of the infected uterus and ovaries. Of course, this is a major operation, and in dogs that are very weak from the toxic effects of the infection over a long period, it is not always successful.
In dogs that are poor surgical risks drainage of some of the purulent material may be attempted and antibiotics and fluids administered until the dogs are strong enough to withstand surgery.
Prevention of pyometra can be achieved by the early desexing of female dogs that are not required for breeding. If progesterones are to be administered to a bitch, do so in consultation with your veterinarian.
Prolonged administration should be carefully monitored and any abnormal discharges should be investigated. Consult your veterinarian if your aged female has an abnormally long season or has any sign of purulent discharge after the season.