Pyometra

Pyometra

What is pyometra?

Pyometra is an infection of the uterus. It is a serious condition that can become life-threatening if not treated. Pyometra occurs as a consequence of hormonal changes effecting the lining of the uterus. Following oestrus ("heat"), progesterone levels remain elevated for 8-10 weeks and thicken the lining of the uterus in preparation for pregnancy. If pregnancy does not occur for several oestrus cycles, the lining continues to increase in thickness until cysts form within it. The thickened, cystic lining secretes fluids that create an ideal environment in which bacteria can grow.

Are there other situations that cause the changes in the uterus?

Yes. The use of progesterone-based drugs can do this. In addition, oestrogen will increase the effects of progesterone on the uterus. Drugs containing both hormones are used to treat certain conditions of the reproductive system.

How do bacteria get into the uterus?

The cervix is the gateway to the uterus, it remains tightly closed except during oestrus. When it is open, bacteria that are normally found in the vagina can enter the uterus rather easily. If the uterus is normal, the environment is adverse to bacterial survival; however, when the uterine wall is thickened and cystic, perfect conditions exist for bacterial growth. In addition, when these abnormal conditions exist, the muscles of the uterus cannot contract properly. This means that bacteria that enter the uterus cannot be expelled.

When does it occur?

The typical time for pyometra to occur is about 1-2 months following oestrus. Pyometra may occur in young to middle-aged dogs; however, it is most common in older dogs. After many years of oestrus cycles without pregnancy, the uterine wall undergoes the changes that promote this disease.

What are the clinical signs of a dog with pyometra?
The clinical signs depend on whether or not the cervix is open. If it is open, pus will drain from the uterus through the vagina to the outside. It is often noted on the hair under the tail or on bedding and furniture where the dog has laid. Fever, lethargy, anorexia, and depression may be present.

If the cervix is closed, pus that forms is not able to drain to the outside. It collects in the uterus causing distension of the abdomen. The bacteria release toxins which are absorbed into the circulation. Bitches with A closed pyometra often become severely ill very rapidly. They are anorectic, very listless, and very depressed. Vomiting or diarrhoea may be present.

Toxins from the bacteria affect the kidney's ability to retain fluid. Increased urine production occurs, and the dog drinks an excess of water. This occurs in both open- and closed-cervix pyometra.

How is it diagnosed?
Pyometra is always suspected in a ill entire bitch that is drinking an increased amount of water and has had a season within the last 1 - 2 months. Diagnosis is more obvious if there is a vaginal discharge or enlarged abdomen. Blood tests will usually reveal an increased white blood cell count (indicating infection) and often elevated kidney enzymes ( indicating kidney damage due to the bacterial toxins). However, all of these abnormalities may be present in any dog with a major bacterial infection. If we need confirmation of the diagnosis of pyometra then x-rays of the abdomen are taken to look for an enlarged uterus.

How is it treated?

The best treatment is to surgically remove the uterus and ovaries immediately. This is called an ovariohysterectomy ("spey"). Bitches with pyometra usually require intravenous fluid therapy as they are often very ill. Antibiotics are given for 1-2 weeks. It is important not to delay presenting your bitch to the vet if you think she may have a pyometra. Delay could cost her her life.

I have a valuable breeding bitch, is there an alternative to surgery?

There is a medical approach to treating pyometra. Prostaglandins are a group of hormones that reduce the blood level of progesterone, relax and open the cervix, and contract the uterus to expel bacteria and pus. They can be used successfully to treat this disease, but they are not always successful and they have some important limitations.

They cause side-effects of restlessness, panting, vomiting, defaecation, salivation, and abdominal pain. The side-effects occur within about 15 minutes of an injection and last for a few hours. They become progressively milder with each successive treatment and may be lessened by walking the dog for about 30 minutes following an injection.
As there is no clinical improvement for about 48 hours dogs that are severely ill are poor candidates.
Because they contract the uterus, it is possible for the uterus to rupture and spill infection into the abdominal cavity. This is most likely to happen when the cervix is closed.

Important statistics that you should know about this form of treatment:

The success rate for treating open-cervix pyometra is 75-90%.
The success rate for treating closed-cervix pyometra is 25-40%.
The rate of recurrence of the disease is 50-75%.
The chances of subsequent successful breeding is 50-75%.

What happens if neither of the above treatments are given?

The chance of successful treatment without surgery or prostaglandin treatment is extremely low. If treatment is not performed quickly, the toxic effects from the bacteria will be fatal. If the cervix is closed, it is also possible for the uterus to rupture, spilling the infection into the abdominal cavity. This will also be fatal.

What can I do to prevention pyometra in my bitch?

If you do not intend to breed from your bitch our advice is that you should have her speyed. The best time to do this is about 2 months following the end of her first season. Read more about this and the other health advantages of neutering your bitch.