Vaginitis in dogs: A simple approach to a complex condition

Illustration by Joel and Sharon Harris

Vaginitis, by its simplest definition, is inflammation of the vagina. Vaginitis is not, however, a simple condition. Its pathophysiology is poorly understood, prohibiting our ability to treat it specifically. This article is a review of what we know about this common condition, with suggestions for diagnosis and treatment.

FORMS OF VAGINITIS

Two forms of vaginitis are recognized in dogs-juvenile, or puppy, vaginitis and adult-onset vaginitis.

What's new in canine vaginitis? 

Within the rapidly expanding world of new veterinary diagnostics, drugs, and other therapeutic modalities, you may be surprised to learn the latest on this condition hasn't changed in over a decade.

The dvm360 editors asked the author of this article, Dr. Margaret Root Kustritz, if we could update the text with the latest findings as of April 2019. Her response? Apart from a few published case reports and review articles in the last 10 years, there have been no new developments in relation to the identification and treatment of canine vaginitis and, disappointingly, no new research either. Dr. Root Kustritz says veterinarians would benefit from new studies-such as investigation of allergies, urinary incontinence, and other possible underlying causes of vaginitis, along with appropriate new treatment options-to shed new light on this frustrating and common disorder.

So until that research receives funding, you can get updated on-or simply reaffirm what you may already know about-managing dogs with vaginitis in this article.

Juvenile vaginitis is vaginal inflammation and associated clinical signs in bitches that have not yet undergone puberty. No breed predisposition has been reported. Most affected dogs show minimal or no clinical signs; scant mucoid discharge at the vulvar lips is most commonly described. Often this discharge is an incidental finding at a routine physical examination, seen as whitish-yellow discharge gluing together the vulvar lips. Some bitches may exude a large enough volume of discharge to be of concern to the owner, and some bitches may lick at the vulva.

Adult-onset vaginitis is much more common in spayed bitches than in intact ones. The age at onset of clinical signs is variable, and no breed predisposition has been reported. In 80% to 90% of cases, the presenting complaint is mucoid to purulent vulvar discharge.1,2 The next most common presenting complaints are vulvar licking, pollakiuria, and urinary incontinence.2 Occasionally, dogs have clinical signs associated with a concurrent disease (e.g. diabetes mellitus or hepatic disease) that exacerbates the vaginitis.

DIAGNOSTIC OVERVIEW

Figure 1. Diagnosing and treating canine vaginitis (click to enlarge).Several physiologic and pathologic conditions in dogs may be evidenced by vulvar discharge and vulvar licking. Such physiologic conditions include estrus, whelping, and postpartum lochia. Such pathologic conditions may arise from the reproductive tract (e.g. ovarian remnant syndrome, pyometra or uterine stump pyometra, vaginitis, vaginal neoplasia, a vaginal foreign body such as a foxtail), the urinary tract (e.g. urinary incontinence, a urinary tract infection [UTI], urinary tract neoplasia), or a systemic condition (e.g. canine brucellosis, canine herpesvirus infection, a coagulopathy, atopy).

Diagnostic test are the same for juvenile and adult-onset vaginitis. These tests include a cytologic examination of vaginal epithelial cells and vaginal discharge, vaginal and urine bacterial cultures and antimicrobial sensitivity testing, urinalysis, a digital vaginal examination, and vaginoscopy (Figure 1). Juvenile dogs, who generally have mild, self-limiting vaginitis, may not require a complete work-up.

Cytologic examination

Figure 2. Cytologic examination of a vaginal specimen from a dog with vaginitis reveals noncornified vaginal epithelial cells and polymorphonuclear cells (modified Wright's stain; 100X). A cytologic examination of the vaginal epithelium in dogs with vaginitis reveals noncornified epithelial cells (Figure 2). Vaginal discharge usually appears mucoid to mucopurulent on cytologic examination. In a survey of 15 dogs with vaginitis, 33% had mucoid discharge, 20% had mucopurulent discharge, and 27% had purulent discharge.1 Occasionally, dogs with vaginal inflammation have no vulvar discharge.1,2 Rarely, the discharge is blood-tinged; however, true hemorrhagic discharge has not been described in dogs with uncomplicated vaginitis.1,2

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 fro4m dogs with no history of reproductive tract disease, and fungal vaginitis in dogs is rare in North America.8,9

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

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

Because cytologic or culture sample collection may induce erythema, you may be tempted to do vaginoscopy first. However, vaginoscopy requires lubrication to introduce the instrument, so the vagina may be adulterated by the lubricant or by cells or debris pushed into the vaginal vault with the vaginoscope, creating artifactual change in other diagnostic tests. I prefer to collect all other samples first and perform vaginoscopy last, recognizing that artifactual changes may have occurred.

Vaginoscopy also helps you assess discharge present in the vaginal vault; vesicular lesions (e.g. seen with canine herpesvirus infection) or lymphoid follicles (e.g. seen as a nonspecific indicator of inflammation);16,17 urine pooling, which may be best identified by performing vaginoscopy in recumbent and standing patients9; masses; and foreign objects.

Other important diagnostic tests

Finally, a complete work-up for vaginitis in dogs, especially those with adult-onset disease, includes performing serologic testing for canine brucellosis, which may be exhibited as persistent mucopurulent vulvar discharge,18 and ruling out systemic disease by performing a complete blood count and serum chemistry profile.

Canine herpesvirus infection in prepubertal bitches or spayed adult female dogs is associated with vesicular or firm lesions on mucosal surfaces, including the vagina, and no other clinical signs.16,17 Unfortunately, tests for canine herpesvirus infection are imprecise and not clinically useful, so this infection may only be suspected after other causes have been ruled out.19

TREATING VAGINITIS

How you treat an affected dog depends on the form of vaginitis present. Below is a summary of suggested therapies based on the diagnostic findings.

Juvenile vaginitis

In most bitches with juvenile vaginitis, physical and cytologic examinations reveal mucoid to mucopurulent vaginal discharge and mild erythema in the vaginal vault, and vaginal bacterial cultures reveal no significant growth. Most cases will resolve spontaneously with time, and conservative therapy is the norm. If the only clinical signs are those that you find incidentally, treatment is not necessary. Excessive discharge or vulvar licking and marked growth of aerobic bacteria from a vaginal sample warrant appropriate antibiotic therapy. Dogs may benefit from twice-daily cleaning of the perivulvar area with baby wipes or a nonalcohol-based otic cleanser.9 Douching, or flushing of the vaginal vault, has not been reported to be an effective therapy in dogs with juvenile vaginitis.

A common question is, "Should dogs with juvenile vaginitis be allowed to go through one estrous cycle before ovariohysterectomy?" No studies have evaluated whether this would be beneficial. In a retrospective study describing seven dogs with juvenile vaginitis that were left intact, three improved after one estrous cycle, one improved after two estrous cycles, and three showed no change after multiple estrous cycles but had subsequent resolution by 3 years of age.2 These results suggest that it may not be the hormonal changes and associated vaginal epithelial changes of estrus that resolve the vaginitis but that a dog's increasing immunocompetence with maturity may be of benefit. The known increased incidence of mammary neoplasia in bitches left intact is a strong incentive not to leave bitches intact as a treatment for vaginitis unless severe clinical signs are present.

Adult-onset vaginitis

The most common primary problems reported in dogs with vaginitis are UTIs, reported in 26% to 60% of cases; vaginal anatomical anomalies, reported in 20% to 36% of cases; and systemic disease, reported in 15% of cases.1,2

Be aware that in most bitches (73% in one study) vaginitis resolves regardless of the therapy used.2 I have had success in asking owners to keep track on a calendar when clinical signs are evident. This objective record better permits the owner and the veterinarian to determine the frequency and severity of clinical signs and to monitor progress with therapy.

Bacterial infections. In some dogs, it is difficult to know whether vaginitis caused a UTI or if a UTI caused vaginitis. Concurrent bacterial cultures of vaginal vault samples obtained by using a guarded vaginal swab and a urine sample collected by cystocentesis may permit you to localize disease at the time of presentation.

Treatment for a UTI is based on urine bacterial culture and antimicrobial sensitivity testing. Significant growth from vaginal bacterial culture samples also prompts appropriate antibiotic therapy. Empirical therapy is not recommended. Mycoplasma species organisms and Escherichia coli may emerge in the vagina during inappropriate antibiotic therapy, strongly arguing against indiscriminate use of antibiotics.20

Anatomical abnormalities. Vaginal anomalies are a common underlying cause of vaginitis, possibly because the anomaly permits urine to pool and irritate the vaginal mucosa. Urine pooling is best evidenced by positional urinary incontinence (urine leakage when the dog changes position such as when arising or jumping up), or identified by vaginoscopy. The relevance of vaginal anomalies in the absence of urine pooling is unknown. Surgical repair of vaginal anomalies depends on the type and extent of the anomaly present.

Urinary incontinence. In most cases, urinary incontinence associated with vaginitis is presumed to be urethral sphincter mechanism incontinence, formerly called estrogen-responsive urinary incontinence. Treatment with diethylstilbestrol (0.1 to 0.2 mg/kg orally, maximum dose = 1 mg) once a day for five days, tapering to twice a week, or phenylpropanolamine (1 to 1.5 mg/kg orally) two or three times a day may be of benefit in some bitches.

Perivulvar or perivascular dermatitis. An atrophic, or juvenile, vulva with excessive skin folds has not been reported as a primary cause of vaginitis in the absence of concurrent perivulvar dermatitis. Overweight dogs with urinary incontinence are prone to perivascular dermatitis because of excessive perivulvar skin folds and persistent moisture and urine scald. In one study, 18 dogs with vaginitis had complete resolution of clinical signs after vulvoplasty (episioplasty).21

Systemic disease. Concurrent disease may be identified after performing a complete blood count and serum chemistry profile. Dogs with uncomplicated vaginitis generally have normal results.2,22 Treat any underlying systemic disease, such as diabetes mellitus or hyperadrenocorticism, first, and if the vaginitis does not resolve, treat as for idiopathic vaginitis.

Idiopathic vaginitis. Many dogs have idiopathic vaginitis, so several symptomatic therapies have been described. Estrogenic agents such as diethylstilbestrol may help control subclinical urinary incontinence and may enhance the movement of white blood cells into the vaginal vault and increase vaginal wall elasticity. Do not use diethylstilbestrol in dogs that have not achieved full adult height because it may cause premature closure of the physes of long bones. Phenylpropanolamine may also help control subclinical urinary incontinence.

Histologic examination of vaginal wall biopsies suggests that many dogs with clinical vaginitis have lymphoplasmacytic infiltration of the wall as a component of inflammation.9 Thus, glucocorticoid therapy may be beneficial in some bitches. To avoid exacerbating a problem likely already distressing to the owner, I do not use glucocorticoids in dogs with urinary incontinence.

As in juvenile dogs, douching has not been reported to be an effective therapy for vaginitis in adult spayed female dogs.

Finally, I have had some success with diphenhydramine or hydroxyzine in dogs with clinical signs of vaginitis and a history or clinical findings suggestive of concurrent atopy (Figure 1).

CONCLUSION

Better identification of conditions known to be primary factors in dogs with vaginitis, such as vaginal anatomical anomalies, concurrent systemic disease, and, potentially, atopy, will better permit practitioners to understand and treat vaginitis. Most therapy for vaginitis is symptomatic because most cases are idiopathic. Vaginitis can be frustrating for owners and veterinarians alike, so it is best to be honest with clients about our limited understanding of its causes and our inability to predict when and if clinical signs will resolve. I find that most clients adhere to my recommendations if the diagnostic and treatment plans are thoroughly explained.

Margaret V. Root Kustritz, DVM, PhD, DACT

Department of Veterinary Clinical Sciences

College of Veterinary Medicine

University of Minnesota

St. Paul, MN 55108

References

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