Comparison of digital radiography, ultrasonography, and positive contrast vaginourethrography for determining reproductive status of female cats.

It is not always possible to identify female cats that have undergone previous ovariohysterectomy based on physical examination alone. An easy, cost-effective method for screening female cats for reproductive status would be helpful for avoiding unnecessary exploratory laparotomies. The purpose of this prospective study was to compare diagnostic sensitivities of digital radiography, ultrasonography, and positive contrast vaginourethrography for determining reproductive status in female cats. Sixty-seven recently euthanized female cats of unknown medical history and reproductive status were randomly selected and included in the study. Digital abdominal radiography, digital abdominal radiography with compression, abdominal ultrasonography, and positive contrast vaginourethrography were performed in sequence by a board-certified veterinary radiologist and a second-year radiology resident. Immediately following diagnostic imaging procedures, necropsy was performed. Ultrasonography of the uterus had the highest sensitivity (86%) for determining reproductive status of all the imaging modalities tested. The specificity was 88%, and the positive predictive value and negative predictive value were 96% and 68%, respectively. The calculated sensitivities and specificities of other modalities were as follows: digital radiographs (28%, 100%), digital compression radiographs (58%, 100%), and vaginourethrography (32%, 100%). Based on McNemar's test statistic, there was a significant difference in the sensitivity of ultrasound compared to digital radiographs (P ≤ 0.05), compression radiographs (P ≤ 0.05), and vaginourethrogram (P ≤ 0.05). Findings from the current study indicated that ultrasonography is a sensitive diagnostic test for determining reproductive status in female cats. Although more readily available in private practice and shelters, digital radiography and vaginourethrography are not reliable predictors of reproductive status.