Vaginal bacterial culture
Any infectious component of vaginitis is considered to occur secondary to some underlying cause of inflammation since the
bacteria most commonly cultured from dogs with vaginitis are the normal flora in the vagina, which originate on the skin and
from the rectum (Table 1).3-6 Because the vagina is not sterile, interpret culture results with caution and have the laboratory quantify bacterial growth.
A significant culture result is moderate to heavy (3+ to 4+) growth of one or two bacterial species. Collect culture samples
with a long, guarded instrument, if possible.7 Aerobic bacterial culture is sufficient because Mycoplasma and Ureaplasma species have not been cultured more commonly from dogs with vaginitis than from dogs with no history of reproductive tract
disease, and fungal vaginitis in dogs is rare in North America.8,9
Table 1. Aerobic Bacteria Isolated from Dogs with Vaginitis*
Urinalysis and bacterial culture
UTIs and vaginitis are often concurrent.2 UTIs are frequently caused by bacteria ascending from the distal urethra and surrounding area.10 It is easy to see how vaginal flora overgrowth could cause UTIs and, conversely, how infected urine passing through the
vagina could cause vaginitis.11 Diagnosing a UTI requires collecting urine directly from the urinary tract since free-catch samples will be contaminated
with vaginal contents. Collecting urine by cystocentesis for urinalysis and aerobic bacterial culture is recommended.
Digital vaginal examination
It is important to perform a digital vaginal examination in all dogs with clinical signs of vaginitis. Vaginal anatomical
anomalies (described below) are a common underlying problem in dogs with adult-onset vaginitis. Vaginal strictures or septa can be detected by digital
vaginal examination in 88% of cases.12,13
Vaginoscopy can help you diagnose vaginal anatomical anomalies and assess the degree of erythema of the vaginal mucosa. While
vaginoscopes are marketed for dogs, their length and the diameter of their viewing orifices are similar to that of large otoscope
cones. Thus, a large otoscope cone is adequate for vaginoscopy, revealing vaginal anomalies visible with a vaginoscope in
96% of cases.12,13
Vaginal anomalies described in dogs include
- Strictures, or stenoses, which are circumferential narrowings of the vaginal vault. Theses narrowings are most commonly found
just cranial to the urethral papilla.
- Vaginal septa, which are pillars or walls of tissue within the vagina.
Both these anomalies result either from abnormal dissolution of the appropriate portions of the paired paramesonephric (müllerian)
ducts or abnormal joining of the paramesonephric ducts with the caudal urogenital sinus.
The incidence of vaginal anomalies in dogs has not been reported. Anecdotal evidence suggests that many dogs with vaginal
anomalies do not have genitourinary disease. One study attempted to create an objective measure of the degree of stricture
based on measurements of the vagina and vestibule from vaginograms.14 This study did not specifically address dogs with vaginitis but did, in general, show that dogs with severe vaginal strictures
and associated disease of the genitourinary tract had a poor response to any treatment modality.14
The vaginal mucosa should be the same rosy-pink color as healthy oral mucous membranes. While vaginitis cannot be diagnosed
without evidence of vaginal inflammation, be aware that some diagnostic tests (e.g. vaginal swab, vaginoscopy) readily cause vaginal erythema and that some dogs have markedly erythematous vaginal mucosa with
no other evidence of vaginitis. In a survey of eight dogs, four of which were control dogs and four of which had clinical
vaginitis, two of the normal dogs had mild to moderate erythema of the vaginal mucosa. Three of the eight dogs developed erythema
secondary to diagnostic testing.15