The word “pyometra” is derived from latin “pyo” meaning pus and “metra” meaning uterus. The pyometra is an abscessed, pus-filled infected uterus. Toxins and bacteria leak across the uterine walls and into the bloodstream causing life-threatening toxic effects. The uterus itself dies releasing large amounts of pus and dead tissue into the abdomen. Without treatment death is inevitable. Prevention of this disease is one of the main reasons for routinely spaying female dogs.
Classically, the patient is an older female dog. Usually, she
has finished a heat cycle in the previousl 1-2 months. She
has a poor appetite and may be vomiting or drinking an
excessive amount of water. In the more usual “open
pyometra” the cervix is open and the purulent uterine
contents is able to drip out thus a smelly vaginal discharge is
usually apparent; however, there is also a form of pyometra
called a “closed pyometra” where the cervix is closed. In
these cases, there is no vaginal discharge and the clinical
presentation is more difficult to diagnose. These patients also
tend to be sicker than those with open pyometra due to
retention of the toxic uterine contents.
A radiograph showing a closed pyometra (Thanks to Alta Mesa Animal Hospital)
Lab work shows a pattern typical of widespread infection which is often helpful in narrowing down the diagnosis. Radiographs may show a gigantic distended uterus though sometimes this is not obvious and ultrasound is needed to confirm the diagnosis.
With each heat cycle, the uterine lining engorges in preparation for pregnancy. Eventually, some tissue engorgement becomes excessive or persistent (a condition called “cystic endometrial hyperplasia”). This lush glandular tissue is ripe for infection (recall that while the inside of the uterus is sterile, the vagina below is normally loaded with bacteria.). Bacteria ascend from the vagina and the uterus becomes infected and ultimately pus-filled. Effects on the uterine tissue accumulate with each heat cycle which means pyometra is much more common in older females as they have experienced many heat cycles.
The usual treatment for pyometra is surgical removal of the uterus and ovaries. It is crucial that the infected uterine contents do not spill and that no excess hemorrhage occurs. The surgery is challenging especially if the patient is toxic. Antibiotics are given at the time of surgery and may or may not be continued after the uterus is removed. Pain relievers are often needed post-operatively. A few days of hospitalization are typically needed after the surgery is performed.
It is especially important that the ovaries be removed to remove future hormonal influence from any small stumps of uterus that might be left behind. If any ovary is left, the patient will continue to experience heat cycles and be vulnerable to recurrence.
While pyometra surgery amounts to the same end result as routine spaying, there is nothing routine about a pyometra spay. As noted, the surgery is challenging and the patient is in a life-threatening situation. For these reasons, the pyometra spay typically costs five to ten times as much as a routine spay.
- The infected uterus is resolved rapidly (in an hour or two of surgery).
- Extremely limited possibility of disease recurrence.
- Surgery must be performed on a patient that could be unstable.
In the late 1980’s another treatment protocol became available that might be able to spare a valuable animal’s reproductive capacity. Here, special hormones called “prostaglandins” are given as injections to cause the uterus to contract and expel its pus. A week or so of hospitalization is necessary and some cramping discomfort is often experienced. The treatment takes place over the course of a week. This form of treatment is not an option in the event of a “closed” pyometra as described above plus, the dog must be bred on the next heat cycle. If she is not bred or does not conceive puppies on the next heat cycle, the recurrence rate of pyometra may be as high as 77%. After recovery from pyometra, the uterus is damaged and may not carry a litter normally (50-65% pregnancy rates with breeding have been published). Unless the dog has great value to a breeding program, it may not be worth it to attempt prostaglandin treatment.
- There is a possibility of future pregnancy for the patient (though often there is too much uterine scarring).
- Surgery can be avoided in a patient with concurrent problems that pose extra anesthetic risk.
- Pyometra can recur.
- The disease is resolved more slowly (over a week or so).
- There is a possibility of uterine rupture with the contractions. This would cause peritonitis and escalates the life-threatening nature of the disease.
- Breeding should occur on the very next heat cycle.
Spaying represents complete prevention for this condition. Spaying cannot be over-emphasized. Often an owner plans to breed their pet or is undecided, time passes, and then they fear she is too old to be spayed. The female dog or cat can benefit from spaying at any age. The best approach is to figure that pyometra is highly likely occur if the female pet is left unspayed; any perceived risks of surgery are very much out-weighed by the risk of pyometra.
The main difference between the feline and canine pyometra is that the cat with a pyometra appears surprisingly well despite the serious medical condition present. Usually the copious purulent discharge is noted but the cat is eating and grooming normally as if nothing much is going on. As with the dog, the pyometra can be open or closed and can be treated with surgery or with prostaglandins. Cats are usually in better general health when approaching surgery and tend to have a faster recovery than dogs.
Page last updated: 3/6/2012