Histopathological, endocrine and microbiological findings in bitches showing pyometra: a prospective study

Abstract

This prospective study was conducted at the University Veterinary Hospital between 2023 and 2024. Ovariohysterectomies were performed on 40 bitches diagnosed as pyometra, following ultrasound assessment. Before surgery, a complete clinical evaluation and blood analysis were conducted. After the uterus was removed, both macroscopic and microscopic (histopathological) evaluations of the uterus and ovaries were performed; in addition, microbial isolation and identification were performed to determine the predominant bacteria, and antibiotic sensitivity was assessed. The affected bitches were over 8 years old in 82.5%, and there was a higher incidence (55.5%) in females between 1-10 kg. Vaginal discharge and lethargy were the most reported symptoms associated with pyometra in more than 70% of cases. Regarding, hematological and biochemical findings, elevated leukocyte counts were observed in 70% of the bitches, with 77.5% showing neutrophilia and 20% exhibiting kidney alterations (abnormal creatinine/blood urea nitrogen levels). Corpora lutea and follicular cysts were the structures mainly observed in the ovaries of the bitches (85.0%), and endometrial hyperplasia with endometritis was found in 82.5% of the cases. These conditions often coexisted with the presence of corpora lutea and follicular cysts in 100%. Additionally, progesterone levels were higher in the presence of corpora lutea (9.8 ± 1.5 ng/ml) and tumors (20.0 ng/ml). Escherichia coli was predominantly isolated (67.65%), followed by Staphylococcus spp. (8.82%), Enterobacter spp. (5.88%) and Proteus spp. (2.94%) with high rates of resistance to Amoxicillin-clavulanic acid and Cephalexin (92.31%), as well as to Clarithromycin and Tetracycline (88.46%). Enrofloxacin, Pradofloxacin and Ciprofloxacin were the antibiotics more effective to inhibiting bacterial growth. The results of this study confirmed a strong correlation between the presence of corpora lutea, high progesterone levels and the development of endometrial hyperplasia with endometritis. In conclusion, surgical intervention, as well as medical treatment, requires antimicrobial therapy adapted to the resistance patterns to ensure the recovery of the bitches. Based on the resistance data obtained, this study recommends the use of fluoroquinolones and advises against the use of Amoxicillin-clavulanic acid, cephalosporins, tetracyclines and Gentamicin, to prevent the further emergence of multidrug-resistant microorganisms.