Should I Spay My Dog And What Is A Pyometra Anyway?

“Stinky Rose” is one of our cutest little patients, but at age 8 she had not yet been spayed.  About two weeks after being in heat last year, she became severely ill.  She had a fever, stopped eating, and was drinking excessive amounts of water all of a sudden.  She also had a mild milky discharge from her vulva.  Stinky Rose had an infection in her uterus called a pyometra, and she underwent an emergency ovariohysterectomy, or spay procedure.  No longer a routine procedure, and with high risk of infection spreading, her surgical expenses were nearly 4 times higher than the discounted routine spay she would have undergone had she had this taken care of before this happened. And her chances of a smooth recovery were now much worse. Luckily, the uterus was able to be removed without rupturing, and the infection contained, before she became septic.   In a few days after hospitalization, she was able to go home and fully recover.  
 

Photo Credit: http://www.cannonvet.com/spay.htm

Dogs have a reproductive cycle that is unlike human cycles.  Female dogs will go into “heat” every 6 months and it is during the heat cycle that they are able to get pregnant.  The heat cycle is often distinguishable to breeders by a bloody vaginal discharge that lasts for about 2 weeks.  Unlike a human menses where bleeding is due to shedding of the uterine lining when a woman is not impregnated, the bloody discharge during the canine estrus cycle is caused by the effects of estrogen on the uterus.  There is no “shedding” per se and as such, no cramps, and no active turnover of the lining of the uterus.  The bleeding in this case indicates a fertile and receptive uterus.

Dog uterus with pyometra

Normal-sized dog uterus

When a dog fails to be impregnated after her estrus or heat cycle, she is prone to cystic endometrial hyperplasia. This is because the uterine wall has been stimulated and is responsive.  Because the lining of the uterus becomes thickened and vascular, bacteria, which can more easily enter when the female dog is susceptible and her cervix is open, can get trapped in this very fertile environment.  The cervix normally closes after the heat cycle and in some cases, this can trap unwanted bacteria and lead to a serious infection.  If the cervix is open enough to allow for drainage of the infection, one will see a purulent malodorous discharge.  If the cervix is only partially open or closed, the uterus will swell and become filled with pus and could eventually rupture.  The infected uterus is known as a pyometra.  A closed pyometra does not have a way to drain and is more dangerous because there are less outward signs and more risk of rupture.  Rupture can lead to an acute peritonitis, or abdominal cavity infection, similar to what happens with a ruptured appendix in people.  This can be life threatening.

If we spay a female dog before her first heat cycle, she will avoid the risk of pyometra, which could potentially happen after every heat cycle.  She is also more than 100 times less likely to have a malignant breast tumor if spayed before her first heat cycle, and 500 times less likely than she would be after her second heat cycle. 

It is safer and healthier for your female pet dog not to have these odds working against her.  Please spay your pet before her first heat cycle whenever possible, and avoid these unnecessary risks.