Development of an ultrasonographic grading system for cystic endometrial hyperplasia in dogs

Cystic endometrial hyperplasia (CEH) is a common reproductive disorder in bitches, characterized by cystic distention of the endometrial glands. While often asymptomatic, CEH can increase the risk of pyometra and infertility. Diagnosis is typically performed via ultrasound, but interpretation of findings remains subjective due to the lack of a standardized documentation system. Aim of this study was to develop and validate a standardized ultrasonographic grading system for CEH to improve diagnostic consistency and reproducibility. CEH videoclips were initially evaluated subjectively by three experienced veterinarians, revealing poor interobserver agreement and highlighting the need for a more objective approach. Ultrasound video clips of 32 dogs were analysed to identify morphological features that could be used to develop a grading system. Cyst number and cyst size were selected as core parameters, with cyst size categorized as <1 mm, 1-4 mm, or >4 mm. Scoring points were assigned based on the proportion of the uterus affected, and total scores were used to classify CEH as normal, mild, moderate, or severe. Validation using a separate set of videoclips and the grading system led to high interobserver agreement (κ = 0.852; ICC = 0.935), whereas subjective assessment again achieved moderate agreement (κ = 0.392), demonstrating the advantage of structured evaluation. Overall, the proposed grading system provides a more consistent and objective method for CEH documentation. Further prospective studies are needed to assess its applicability in daily practice and to evaluate correlations of CEH grades with pyometra risk and fertility.