Pyometra is a bacterial infection of the uterus in the period after heat when the hormone Progesterone is produced to prepare the uterus for pregnancy. Pyometra can occur in both dogs and cats of any breed. The incidence of pyometra is higher in dogs than in cats because dogs are exposed to natural progesterone (when coming on heat) more often than cats. Pyometra is very common in dogs that are not used for breeding, and can develop at any age.

The Older Dog: The uterus responds to progesterone abnormally. When progesterone prepares the uterus for pregnancy, it causes the wall of the uterus to thicken and an increase in the number of glands. These glands produce a very nutritious secretion for embryo implantation, but unfortunately this is also an ideal environment for bacterial growth. This is very common and the majority of female dogs not used for breeding will develop pyometra.

The Younger Dog: It is unlikely that the uterus will respond abnormally to progesterone. The most common cause of pyometra is oestrogen administration, generally by a veterinarian to prevent pregnancy after mating. Accidental pregnancy is therefore one of the reasons why female dogs should be desexed if they are not going to be used for breeding.

There are two types of pyometras:

Open Cervix Pyometra
The cervix is a structure, which separates the uterus from the vagina. Dogs with an open cervix pyometra have a discharge from the vagina containing pus and blood. This discharge is usually noticed 4 to 8 weeks after the end of heat. Other common symptoms of pyometra include lethargy, depression, inappetance, excessive drinking and urinating, vomiting and diarrhoea. This type of pyometra may be recognised quickly by the experienced owner due to the discharge from the vagina. If left untreated, this pyometra can caused serious damage due to the detrimental effects of the toxins produced by the bacteria.

Closed Cervix Pyometra
Due to the lack of the easily recognizable symptom of vaginal discharge, this pyometra is difficult to detect. The dog will also show symptoms include lethargy, depression, inappetance, excessive drinking and urinating, vomiting and diarrhoea. As the toxins produced by the bacteria are released into the blood stream, these symptoms will get worse. The dog will progressively deteriorate, with worsening dehydration, shock, coma and, eventually, death.

Diagnosis:

1. Blood tests: It is common to get an increase in the total white cells (WBC) in the blood, but normal or low WBC counts do not exclude the diagnosis of pyometra completely. An increase in the total WBC indicates that the body's immune system is combating an infection. The dog may also become anaemic - reduced red blood cells (RBC) in the circulation - because toxins produced by the bacteria can suppress the bone marrow production of RBC. The body often loses its ability to regenerate RBC. Together with the constant blood loss from the infected uterus, the dog will become more anaemic and the pyometra may soon turn into an emergency situation. In severe cases, the dog may need a blood transfusion to compensate for the blood loss.
   
2. Vaginal smear: A smear is made of the vaginal discharge and examined under a microscope. It is possible to visualize the causative bacteria and the WBC produced to combat the infection.
   
3. Ultrasonography: This is the most accurate and non-invasive way to diagnose pyometra. The size of the uterus, the thickness of the uterine walls and the presence of fluid accumulation within the uterus can all be determined by this method. In a closed cervix pyometra, the uterus is identified as a series of large, circular, thin-walled structures in the abdomen. In the open cervix pyometra, the uterus is not as enlarged and may be mistaken for intestine if due care is not taken. Small constant contractions in the intestine distinguish it from the uterus. Ultrasonography can also be used to diagnose pregnancy from 20 days onwards.
   
4. Radiology: This is not a very effective way to diagnose pyometra. The uterus can be seen radiographically, beginning with the third to fourth week post mating and throughout pregnancy. It is abnormal for a non-pregnant dog to have an easily identified uterus. A fluid-dense tube-like structure thicker than the small intestine in the ventral abdomen is typically seen if a pyometra is present.

Without treatment, pyometra is always fatal.

Treatment:

1. Surgery: The most effective way to treat a pyometra is desexing. Desexing involves removing both ovaries and the majority of the uterus. This method directly removes the source of the infection. In healthy dogs with pyometra, full recovery is expected in a few days post surgery. In severely debilitated dogs, complications associated with the toxins in the blood stream can cause organ failure. Using prophalactic antibiotics, checking organ function by blood tests pre-operatively and administering supporting therapy if required, and supplying intravenous fluids to the dog during surgery, can markedly reduce these complications.
   
   
2. Medicines: Prostaglandin is a hormone that can be used to treat pyometra. It stimulates contractions of the uterine muscles and inhibits hormonal changes within the uterus. It can also lead to numerous complications and is not registered for use in dogs, only horses and cattle. It is, however, an established therapy in dogs with pyometra. It is not recommended for use in severely debilitated animals, or in closed cervix pyometras, because of its potentially fatal effect. Prostaglandin can be used together with long courses of antibiotics, chosen on the basis of laboratory culture and sensitivity. This treatment is only suitable for valuable breeding dogs, because of the side effects and high cost of treatment.
   Temporary side effects include restlessness, nausea, abdominal pain, fever and a slow heart rate. These side effects last approximately 45 minutes. Permanent side effects include infertility and increased susceptibility to future pyometra.

"Prevention is better than Cure"

We recommend that female dogs that are not going to be used for breeding be desexed at approximately 6 months of age. Old dogs can be desexed with precautions such as intravenous fluids and pre-anaesthetic blood tests to check for any diseases involving the kidney or liver, as they are the main organs to remove the anaesthetic agent from the body after surgery. The risk of surgery in the healthy dog, irrespective of age, is minimal.