Pyometra is a condition of unsterilised females, usually older than 6 years of age. “Pyo” refers to pus, and “metra” to the uterus. Literally translated, it would mean “bad of pus”. It is a very serious condition and if left untreated for too long, can have deadly consequences. It can be treated very effectively if caught early and taking your animal to the vet when signs first appear can save its life.
Causes of pyometra
The predisposing cause of pyometra is the fact that the female is not sterilised. If the animal comes into heat, but is not mated, it means that the egg cannot be fertilised. Every time she comes into heat, hormonal changes occur, increasing the risk of this disease due to changes in the wall of the uterus. Two types of hormones are secreted by the female ovaries. They are oestrogen and progesterone. As some female dogs get older, their uterus becomes more sensitive to the effects of progesterone. This hormone is responsible for readying the uterus for the coming pregnancy and is also responsible for maintaining an ideal uterine environment for the foetuses to grow in. With each passing heat cycle, progesterone stimulates glands in the wall of the uterus to produce secretions necessary for pregnancy. It also causes the uterine wall to thicken, closes the cervix and increases the blood flow to the uterus. In older females more sensitised to the effects of progesterone, these glands produce excessive amounts of these fluid secretions and eventually these glands become cystic as they do not regress with the end of the cycle. When the next heat starts oestrogen is the major hormone present during the initial period of heat and this stimulates relaxation and opening of the cervix. The open cervix then exposes the uterus to the outside environment where bacteria may migrate into and infect the fluid filled, warm uterus which is essentially the ideal environment for them to grow in. As she then moves into the next period of her cycle, progesterone takes over and stimulates the process all over again and closes the cervix allowing the bacteria to grow uncontrolled in this ideal setting. In response, the body will attempt to fight off the infection by sending large numbers of white blood cells into the uterus. This soup of bacteria and uterine secretions then forms pus which slowly but surely builds up. As the pus increases in quantity the uterine body and horns will slowly start to dilate and expand. The normal uterus has a diameter of approximately 1 cm however this infected uterus can reach a size of 10 cm and larger.
The cervix may close completely or may remain partially open, allowing some of this pussy material to leak out of the uterus. If the cervix remains open, the upside is that some of the pus is allowed to drain, if it is closed however, there is nowhere for the pus to go and it will continue to accumulate, distending the uterus, making this situation a lot more dangerous for your pet.
Toxins produced by bacteria in the uterus may be absorbed into the bloodstream and can have devastating consequences. These toxins may cause a number of secondary problems which include kidney failure and toxic shock to name but two. As fluid keeps building up and the uterus gets bigger, the wall of the uterus gets compromised. The uterus may rupture and pus can leak into the abdomen. This may cause a severe infection of the abdominal cavity which can lead to death of your dog within 4 to 48 hours.
Signs to look out for
This condition usually occurs within two to four weeks after the female dog was on heat. If any of these signs are noted after heat, it is important to take your pet to the vet as quickly as possible.
- Lethargy (weakness and laziness)
- Anorexia (not eating)
- Excessive drinking and urination
- Constant licking of the vulva
- Swollen abdomen
With these clinical signs and a good history from the owner, the vet will have a high suspition of a pyometra, but will have to do more diagnostic tests to make a definitive diagnosis. On a blood smear, the white blood cell count will usually be extremely high. Further tests will include radiographs and in most cases an abdominal ultrasound to visualise the pus filled uterus. Further blood tests might be necessary to evaluate organ function, depending on the severity of the case.
The patient may be placed on a drip with intravenous fluids and started on antibiotics to control the local and systemic infection. The preferred way to treat a pyometra is through surgical removal of the whole uterus and ovaries (ovariohysterectomy), familiarly referred to as spaying your dog. Since the cause of the infection is then removed, prognosis is generally good. In severely debilitated animals, the prognosis will be guarded and these patients will stay on a drip with antibiotics for a couple of days until they have fully recovered. In extreme cases with breeding bitches, other methods can be tried with injection of certain hormones and treatment with antibiotics, but this is definitely not the treatment of choice, as it reduces the survival rate drastically. In very early and milder cases this can be attempted but it is essential to understand that the uterus will have been damaged during the infection and this can markedly reduce fertility. It is important to understand that the preferred method of treatment will always be surgery because this condition is life threatening and any other method attempted can lead to death. Surgery in itself carries a high risk because often time by the time you as the owner notice something is wrong (especially in cases of a closed cervix pyometra) the animal is already in septic shock by the time they are presented to the vet.
Pyometra is a fairly common condition in unsterilised females, and we therefore recommend doing an ovariohysterectomy (spaying) on female dogs at the age of 6 months. Spaying not only prevents a pyometra and unwanted puppies, but it also reduces the risk of mammary cancer if done before the first heat cycle. If a female is used for breeding, it is advisable to spay her after she is past her ideal breeding age to prevent pyometra.
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