CASE 24: Pyometritis in a bitch
Case Information: You are taking a history as a 4th year veterinary student on an 8-year-old intact female Coonhound who presented for dental disease. You take a very thorough history and find yourself talking to the owner about the dog having intermittent vulvar discharge. The owner is not worried about it because the bitch has had it a couple of times and seems okay most of the time. You determine that this is separate from heat; the dog cycles irregularly but has classical serosanguinous discharge while in heat. The owner describes these other episodes as the bitch having thick, yellow discharge, occasionally tinged with blood, for up to several weeks. The most recent heat was about two months ago and the most recent episode of abnormal vulvar discharge was about one month ago. The bitch hasn't been eating well since; that's why they want her teeth cleaned. The bitch was bred once years ago but never had pups. The owner has a good friend who knows a lot about dogs and who told her that this is just pyometritis, that it is common in dogs, and that the antibiotics she'll get when she has her teeth cleaned will take care of it.
Question:
What is pyometritis? What do you think is most likely happening with this bitch and what are your recommendations for further work-up or treatment?
Answer:
Pyometritis is a term used in human medicine for pus in the uterine cavity, often associated with inflammation of the mucosal and muscular uterine layers. This is not something we recognize in bitches, who generally suffer either from metritis or pyometra. Metritis is a primary infection with no underlying pathology and occurs post-partum, making it unlikely in this nulliparous bitch. Pyometra is a secondary infection overlying cystic endometrial hyperplasia (CEH) and is common in middle-aged to older bitches after a heat cycle. This is the more likely cause of vulvar discharge because she is the classic age, she recently went through heat, and she is nulliparous, which appears to increase risk of pyometra. It is difficult to know what happened during the first episode as pyometra generally does not clear spontaneously. It is valuable to pursue the problem at this time, as antibiotic therapy alone is unlikely to resolve pyometra since antibiotics cannot diffuse throughout the pool of purulent fluid in the uterus. My recommendation would be to perform abdominal imaging, ideally abdominal ultrasound, to look for intrauterine fluid and to assess the uterine wall for CEH, and to perform a CBC and chemistry to look for evidence of the body's reaction to disease (leukocytosis with a left shift) and possible secondary disease (azotemia, septicemia). If there is evidence of pyometra, OHE and uterine culture are recommended and should be performed now with the dental cleaning done at another time.