Vestibular, vaginal and urethral relationships in dogs with and without urinary tract disorders

Vestibulovaginal stenosis has been touted as a cause for recurrent urinary tract infections in dogs. The purpose of this study was to objectively evaluate vestibule, vaginal, urethral and urinary bladder anatomy in female dogs and determine the dimensions of the vestibulovaginal junction (aka, vaginal osteum) in dogs with and without lower urinary tract disease. Three groups of dogs were studied: normal intact female dogs (n=14), normal spayed female dogs (n=12), and spayed female dogs (n=19) with lower urinary tract disease. Measurements of specific anatomical structures of the lower urogenital tract were made using three different imaging modalities: conventional vaginourethrography, computed tomography vaginourethrography, and uroendoscopy. Measurements were compared between the three dog groups and the three imaging modalities. There was a significant difference in the majority of measurements between normal intact and normal spayed dogs. There was not a statistical difference in any of the measurements taken between spayed dogs with and without lower urinary tract signs. There was no difference between the calculated vestibulovaginal ratios between spayed dogs with and without lower urinary tract signs. Based on the results of this study, normal vestibulovaginal ratios need to be redefined for both intact and spayed dogs. Without clear evidence that vestibulovaginal stenosis is a true anatomical defect, surgical treatment options should be reevaluated.

Image A is a lateral radiograph following distension of the caudal urinary tract with iodinated contrast medium (vaginourethrogram) in an intact female dog. The urethra is an undulating tubular structure that connects the urinary bladder to the vestibule. The vaginal ostium is the junction between the vagina and the vestibule. Images B and C are transverse CT images made at the level of the vaginal ostium and vestibule, respectively. The round, black structure within the contrast medium filled vestibule on both the radiograph and CT images (A and C) is part of the catheter apparatus inserted into the vestibule to deliver the contrast medium for the procedure. The tip of the catheter can be seen centrally within the vaginal ostium on image B.
A
Lateral radiograph following distension of the caudal urinary tract with iodinated contrast medium (vaginourethrogram) in an intact female dog
BC
Transverse CT images made at the level of the vaginal ostium Transverse CT images made at the level of the vaginal vestibule