Canine Uterine Infections

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There are two different types of uterine infections commonly seen in unspayed female dogs, metritis and pyometra. Both types of infections can cause serious and potentially life-threatening illness if left untreated. Metritis can occur after a dog has puppies, or after breeding. Pyometra, on the other hand, is a uterine infection that is associated with hormonal changes occurring late in the estrus cycle of the dog. Both metritis and pyometra are best treated by having the dog's uterus removed surgically by spaying.


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Postpartum Metritis

One of the times a dog may get metritis is right after she has puppies (postpartum). During the birthing process, the dog's cervix dilates and this gives bacteria an opportunity to enter the uterus and cause infection. Postpartum metritis is much more common following a difficult birthing where intervention was required to manually help the puppies through the birth canal. Additionally, if the dog does not pass her placentas normally after having her puppies, this can also cause postpartum metritis. A dog should be evaluated by a veterinarian for postpartum metritis if she had a difficult birthing, is acting lethargic after having her puppies, has increased vaginal discharge or if one or more of her puppies is sick and not thriving. If left untreated, metritis can cause serious illness in the dam and the puppies, and can harm the future reproductive potential of the dam. The best treatment for serious metritis is to have the dog spayed.


Post-breeding Metritis

When a dog is in heat and stands for breeding, she is entering the phase of her cycle known as "estrus." During this phase her cervix opens for a few days to allow sperm to enter the uterus during mating. Bacterial contamination can be introduced to the uterus at the time of mating and this can cause post-breeding metritis. If a dog is acting sick post-breeding, has malodorous vaginal discharge or has a failure to conceive, she should be evaluated by a veterinarian for post-breeding metritis. Occasionally, low-grade metritis can be treated medically with a combination of prostaglandins and antibiotics. Spaying the dog is always the definitive cure, however.


Open Pyometra

Pyometras are most commonly seen four to eight weeks after a dog has been in heat when there are high levels of progesterone circulating in her body. Progesterone prepares the uterus to support a pregnancy, but these changes also put her at risk for pyometra. Pyometras can occur in unspayed dogs of any age, but are more common in older dogs. Pyometras are very serious life-threatening infections if left untreated. In an open pyometra, the cervix is open allowing the infection to drain into the vagina and out of the dog. A dog with an open pyometra may not be severely ill initially, but will have purulent vagina discharge. She may or may not be lethargic, or have a fever or vomiting. Increased thirst and urination are common in open pyometras due to circulating toxins that cause damage to the kidneys. The best treatment for pyometra is to remove the infected uterus by spaying the dog. Non-surgical approaches to pyometra have been attempted with prostaglandin and antibiotics. There is a chance for reoccurrence of pyometra if medical instead of surgical treatment is used.


Closed Pyometra

Closed cervix pyometra is an immediate and life-threatening emergency for a dog. Infection of the uterus that is unable to drain can lead to septicemia (bacteria in the bloodstream), endotoxemia (toxins in the bloodstream), and can cause the uterus to rupture, spilling the infection into the abdomen and leading to septic peritonitis (severe abdominal infection). A dog with closed cervix pyometra will quickly become depressed and lethargic. She may have a fever, and frequently will have increased thirst and urination due to circulating toxins that are affecting the kidneys. She may have vomiting or diarrhea and show signs of a painful or distended abdomen. Her signs can rapidly progress to systemic shock and death if not treated quickly. The veterinarian who treats your dog for closed cervix pyometra will need to stabilize her before treating the pyometra. Intravenous fluids, antibiotics and other medications to stabilize blood pressure and perfusion to her organs may be necessary. Surgically removing the infected uterus is the best treatment for a closed cervix pyometra; however, there is an increased risk of complications with surgery compared to open cervix pyometra. Dogs will likely require hospitalization and significant aftercare following surgery for a closed cervix pyometra.


By Dr. Heather Beach

DVM360: Surgical and Medical Treatment of Pyometra
The Merk Veterinary Manual: Metritis in Small Animals
The Merk Veterinary Manual: Pyometra in Small Animals

About the Author
Dr. Heather Beach graduated from Tufts Cummings school of Veterinary Medicine in 2007 and has been working at an equine exclusive practice since graduation. She has strong interests and experience in both large and small animal emergency medicine, and in general practice. Dr. Beach writes a regular column for the local publication the "Highland Herald" on horse health and general care.