Julie Besson, Laure Gatel, Tobias Schwarz, Jade Renard, Florence Thierry
Background
Computed tomography (CT) is commonly used to assess lower urogenital tract pathologies in female dogs. While positive contrast media are traditionally employed in CT vaginography, negative contrast (e.g., air) has shown potential for urinary tract evaluation, particularly in human medicine. This study aimed to compare the anatomical visualization quality of positive versus negative retrograde CT vaginography in female dogs with urogenital signs. The hypothesis was that both contrast methods would offer similar visibility for anatomical structures of the lower urogenital tract.
Methods
This was a retrospective, multicenter method comparison study involving 30 female dogs equally divided into positive and negative retrograde CT vaginography groups. CT images were evaluated for visibility of seven anatomical structures using a blinded scoring system (0–2) by two board-certified radiologists. The agreement between reviewers was measured using Cohen’s kappa. Wilcoxon tests were used to compare visualization scores between techniques.
Results
The cervix was more clearly visualized with positive vaginography, while the external urethral orifice was better seen with negative vaginography. Overall, most anatomical structures were similarly visualized with either technique. Positive and negative vaginography both significantly improved visibility compared to post-contrast CT alone for several structures. Interobserver agreement varied, with better consistency noted for structures visualized using vaginography compared to post-contrast CT alone. One complication occurred during a negative vaginography—a vaginal rupture leading to pneumoperitoneum in a dog with a vaginal mass.
Limitations
The primary limitations were the retrospective design, the use of different contrast agents and catheters, and the potential for bias due to the inclusion of different patients in each group. Additionally, incomplete colonic emptying and variable pathological conditions may have influenced imaging results. The study did not control for estrus cycle, and colonic distension may have partially obscured the vagina in some cases.
Conclusions
Negative retrograde CT vaginography provides a viable alternative to positive contrast studies for assessing the lower urogenital tract in female dogs. Both techniques enhance anatomical visualization over intravenous contrast CT alone, and each has specific strengths in delineating particular structures. Negative contrast can be considered when positive contrast is unavailable or contraindicated.
Sagittal CT image of a positive retrograde vaginography post-IV contrast CT in a 7-year-old Cavalier King Charles female spayed dog, presenting for urinary incontinence, recurrent urinary tract infection, and recessed vulva. CT findings were unremarkable. Window width = 2700 HU, window level = 300 HU. Legends: 1: Clitoris Fossa clitoridis scored “2” with good visibility and distension; 2: Vestibule scored “1” with moderate visibility and distension; 3: Cingulum scored “2” with good visibility and distension; 4: Vagina scored “2” with good visibility and distension; 5: Cervix scored “2” with good visibility and distension; 6: Urethral opening ostium scored “2” with good visibility and distension; 7: Urethra scored “1.5” with moderate to good visibility and distension.
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