Stump Pyometra Secondary to Human Topical Estrogen Hormone Exposure in a Spayed Female Chihuahua

A 6 yr old female spayed Chihuahua was presented for evaluation of intermittent vulvar discharge, stranguria, and vomiting. This dog had an ovariohysterectomy as a puppy and did not experience any evidence of estrous until 4.5 yr later. The owner had been using a topical hormone replacement therapy (estradiol spray) twice daily for the duration of the dog's clinical signs of 1 yr. On presentation, the dog had truncal alopecia, comedones, enlarged vulva with a malodorous, and purulent discharge. Bloodwork showed a leukocytosis with a neutrophilia, döhle bodies, and moderate toxic changes. An abdominal ultrasound revealed an enlarged uterine stump with a thickened wall, ovoid projection cranially, and echogenic luminal contents. An exploratory laparotomy identified an enlarged cervical stump. Histopathology revealed chronic suppurative vaginitis with endometritis, necrosis, and intraluminal coccoid bacteria. The dog recovered well from surgery. A baseline estrogen level post operatively was measured at 56.4 pg/mL (<50.0 pg/mL for a spayed bitch), at this time, the dog had been separated from the owner for 7 days. After surgery, the clinical signs disappeared, and the dog's dermatologic changes improved. This is the first reported case of stump pyometra following exposure to the owner's topical estradiol replacement medication.