Dog - Pyometra

What is pyometra?

Pyometra is a not uncommon condition that can affect the uterus of middle aged and older pet bitches that are not regularly bred. Following any normal oestrus, ('heat' or 'season') levels of the hormone progesterone remain elevated for approximately 8-10 weeks. The purpose is to increase the lining of the uterus in order that foetuses can be nourished during pregnancy. If pregnancy does not occur and the level of progesterone does not return to its original pre-oestrus level, the likelihood is that the hormone level will continue to rise resulting in thickening and ultimate cyst formation within the uterine lining. The cysts in turn produce fluid, usually sterile initially. Bacteria enter the uterus via the bitch’s dilated cervix during oestrus, the cyst fluid acts as an excellent substance for the bacteria to grow, leading to development of an acute uterine infection which can quickly become life threatening if undetected and untreated.

Pyometra has thus become a true infection, pyometritis.

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

Progesterone and also oestrogen based drugs are used to treat several conditions of the reproductive system. On occasions these drugs can encourage the signs of pyometra.

When does pyometra occur?

Although it can occur in young bitches, it is most common in middle-aged to older dogs and is, of course, more common in those pets that have had no puppies or perhaps have had only one litter. Typically the condition becomes apparent usually about 4–8 weeks following oestrus.

What are the clinical signs?

These depend on whether or not the cervix is open. If it is open pus will drain from the uterus through the vulva to the exterior. This is open pyometra and usually the first sign is the vulval discharge and the fact that the dog is attempting to continuously clean herself. Fever, lethargy, inappetence and general depression may or may not be present.

If the cervix does not relax, pus continues to accumulate within the uterus. The abdomen is then often distended and the dog can become very ill, extremely rapidly.

The usual signs are lack of appetite, listlessness and depression. The dog usually is very thirsty and may have vomiting and diarrhoea.

How is it diagnosed?

The condition can always be suspected in any bitch that has an increased thirst and has an enlarged abdomen or copious vaginal discharge 4–8 weeks after a season. Urine tests may be used to aid diagnosis.

Diagnostic imaging, (x-rays or ultrasound scans) may also be used to confirm the diagnosis.

What is the treatment?

Surgery is the treatment of choice. Because of the acute nature of closed pyometra in particular, the patient often has to be admitted for stabilisation involving intravenous fluids and antibiotics. Once stabilised surgery to remove the infected uterus and the ovaries is performed.

My dog is only three years old and we were hoping to have a litter. Is there any alternative treatment other than ovariohysterectomy (spay)?

Medical treatment using prostaglandins is theoretically feasible. Prostaglandins are hormones that reduce the circulating blood level of progesterone. They also relax and dilate the cervix and encourage contraction of the uterus which acts to expel the infected contents.

However they do have limitations:

1. They often cause the bitch to show signs of distress including restlessness, panting, vomiting, defecation, salivation, and abdominal pain.
2. It is usually at least 48 hours after commencement of treatment that any clinical improvement will be noted with the patient.
3. If the bitch is severely ill at outset of treatment this may result in death from toxaemia (blood poisoning) before the prostaglandins have brought about any improvement.
4. In cases of closed pyometra the prostaglandin induced uterine contractions could result in a ruptured uterus and associated acute peritonitis (infection in the entire abdomen).

Statistically this form of treatment is most successful for treating open pyometra when it is considered to be over 75% successful. However, the rate of recurrence is at least 60% and the chances of subsequent successful breeding only around 50-60%.