Pyometra in Dogs and Cats

What On Earth is a Pyometra?

               We have had two recent cases of a fairly common condition known as pyometra, so I thought that would be a good topic for this week’s blog.  One dog recovered well, but the other was not so lucky.  So, what is a pyometra?  The term comes from “pyo” which means pus and “metra” which refers to the uterus.  So, a pyometra is a pus-filled uterus, and is considered a life-threatening condition.  Both cats and dogs can develop pyometra, but it is more common in dogs.  Only females who have not been spayed develop this condition. 

               A classic pyometra occurs in an older, unspayed female who has been in heat within the past four to eight weeks before onset of symptoms.  She will usually have pus dripping from her vulva and will display signs of increased drinking, vomiting, loss of appetite, and lethargy.  Some dogs have what is known as a “closed” pyometra where the cervix is closed and no pus can escape.  As you can imagine, these dogs are very ill since the infection cannot escape.  Even with an “open” pyometra, toxins from the uterus spread into the bloodstream causing the dog become very ill and, in some cases, the uterus can rupture spilling pus into the abdomen.  Pyometra can be fatal if not treated.  Surprisingly, other than purulent vulvar discharge, most cats do not act sick when they have a pyometra, though it is still considered a serious, potentially life-threatening problem.

               So, why does the uterus fill with pus in these pets?  In both dogs and cats, the uterine lining engorges when the pet is in heat in preparation for pregnancy whether she is bred or not.  Over time, some of that lining may not fully shed, and the tissue which is rich in nutrients and blood vessels is a great place to support a bacterial infection.  While the uterus itself is sterile, if conditions are right, bacteria within the vagina can travel through the cervix into the uterus causing pyometra. 

               Pyometra is treated by performing an emergency spay and controlling the infection with intravenous fluids and antibiotics.  Spaying the dog or cat to remove the infected uterus is really the best and safest way to treat the infection.  However, if the patient is very ill and unstable, there can be risks.  In very rare cases, if the dog or cat is a valuable breeding animal, treatment with hormones to cause the uterus to contract and expel the pus and with supportive care and antibiotics may be tried, but this treatment is risky and costly and the patient needs to be closely monitored in the hospital for about one week.  The dog must be bred on her next heat cycle.  If she does not become pregnant, the chance of a repeat episode of pyometra is very high.  This is why it is highly recommended to spay any pet with a pyometra rather than attempt medical treatment alone. 

               Spaying obviously prevents pyometra from occurring since the uterus and ovaries are removed.  This is one reason why we always recommend spaying any female who is not a breeding or show dog or cat.  The risk of pyometra and of mammary tumors greatly increases in unspayed females as they age, and are far more serious than any risks from anesthesia or complications from the spay surgery itself.  Performing an emergency spay on a pet who is ill from pyometra is much riskier than spaying a healthy pet, and the cost of a routine spay is also far less than an emergency spay and treatment for pyometra. 

               If you have an unspayed female, consider having her spayed to prevent this problem.  And, if your dog or cat shows any of the symptoms described within a month or two of having been in heat, please have her checked out right away.  Prompt treatment of pyometra can save her life. 

               This blog brought to you by the Patton Veterinary Hospital serving Red Lion, York and the surrounding communities.