General considerations

It is extremely difficult to separate the various diseases of the vagina, vestibule and vulva into usable categories, often because the anatomical structures are contiguous, are affected by a similar process, and because submission sheets provided by submitting veterinarians are not always specific in describing the distribution of lesions.

I have chosen to group the lesions based on pathogenetic grounds.

The common diseases submitted for surgical biopsy examination are listed below. As this is a Canadian study, diseases like canine transmissible venereal tumour are few, because there are few stray dogs.

There are many clinical reviews of vaginal and vestibular disease and some references are listed below.

Submissions to Yager Best Surgical Pathology include the following

Disease of the vulva

Disease of the Vulva, Labia and Perivulval Skin

Juvenile or recesssed vulva

A recessed vulva is when the vulva is surrounded by perivulval skin that extends past the labia. There is no accurate definition or measure that determines exactly when a vulva is recessed, and the position of the vulva relative to the pelvis is not assessed. It may be that the perivulval skin folds become excessive so the 'recession' of the vulva may be relative to the skin. It is a clinically recognized condition that is particularly identified when a dog licks at the vagina, has incontinence, vaginitis, perivulval dermatitis or other sign indicating inflammation or irritation of the area. Other names for this condition include vulval hypoplasia

The pathogenesis is not proven, but early ovariohysterectomy was an accepted predisposing situation. Obesity so that the perivulval skin folds are exaggerated, is also implicated. Hammel and Bjorling (2002) studied dogs with recessed vulva and underwent vulvoplasty, where the perivulval folds were removed. They found that 7 of 34 dogs were intact yet still had a recessed vulva, so early ovariohysterectomy is not a cause in all cases. Ovariohysterectomy does affect the conformation of the vulva, especially when surgery is done during the prepubertal period. There was not sufficient information to assess the effect of obesity in their study.

Recessed vulva is implicated in urinary incontinence, urovagina, vaginitis and perivulval dermatitis. The effect of vulvoplasty in the study by Hammel and Bjorling (2002) was to eliminate vaginitis and perivulval dermatitis suggesting that conformational factors predispose bitches to these diseases.

It is suggested that a 'recessed' vulva prevents complete elimination of urine, and that urovagina may develop. This and the fold of skin around the vulva would predispose to inflammation and pyoderma.

Crawford and Adams (2002) found that dogs with a recessed vulva also was likely to have severe vestibulovaginal stenosis. Dogs with vaginitis responded to vulvoplasty if there was not severe stenosis. Likewise, Lighter et al (2001) found that surgery to remove the skin folds resulted in resolution of the perivulvar dermatitis and chronic urinary tract infection associated with this.

A recessed vulva is a common condition. Wang et al (2006) reported on 19 dogs with urinary tract disease and 12 normal dogs. 3 of the normal and 10 of the clinically affected dogs had recessed vulvas.

Palerme et al (2021) examined a large population of dogs and found 36 in 250 dogs. It was more common in overweight dogs and spayed dogs, especially those spayed at less than 1 year of age. They were not at increased risk of urinary tract infection or perivulval dermatitis.

Crawford JT, Adams WM (2002) Influence of vestibulovaginal stenosis, pelvic bladder, and recessed vulva on response to treatment for clinical signs of lower urinary tract disease in dogs: 38 cases (1990-1999). J Am Vet Med Assoc. 221(7): 995-999.

Hammel SP, Bjorling DE. (2002) Results of vulvoplasty for treatment of recessed vulva in dogs. J Am Anim Hosp Assoc. 38(1): 79-83.

Lightner BA, McLoughlin MA, Chew DJ, Beardsley SM, Matthews HK. (2001) Episioplasty for the treatment of perivulvar dermatitis or recurrent urinary tract infections in dogs with excessive perivulvar skin folds: 31 cases (1983-2000). J Am Vet Med Assoc 219(11): 1577-1581

Palerme JS, Zellner E, Leonard S, Viall AK, Berger DJ. Characterization of recessed vulvas in dogs. J Am Vet Med Assoc. 2021 Oct 1;259(7):744-748.

Wang KY, Samii VF, Chew DJ, McLoughlin MA, DiBartola SP, Masty J, Lehman AM. (2006) Vestibular, vaginal, and urethral relations in spayed dogs with and without lower urinary tract signs. J Vet Intern Med. 20(5): 1065-1073.

Vulval and perivulval inflammation

Vulvitis and perivulvar dermatitis (external skin)

Inflammation of the vulva and perivulval skin is known by several names including skin fold pyoderma, perivulvar pyoderma, mucocutaneous pyoderma of the vulva, perivulvar dermatitis, and intertriginous dermatitis. Strictly speaking, mucocutaneous pyoderma occurs at the junction of the mucous and cutaneous tissues, and vulvar skin fold pyoderma occur under the fold. Both areas can be affected simultaneously.

Perivulvar dermatitis is a common condition, especially in obese dogs and those dogs with prominent perivulvar skin fold that cover the vulva (also called recessed vulva, or vulvar hypoplasia). It has been associated with vestibulitis, vaginitis and urinary tract infection.

Resolution of dermatitis is often acheived with surgery to remove the excessive skin folds (vulvoplasty, episioplasty) (Lighter et al 2001, Hammel and Bjorling 2002).

The pathogenesis of perivulvar dermatitis is believed to be similar to other mucocutaneous and skin fold pyodermas, with the presence of excessive moisture, warmth and secretions and exudates providing a suitable region and substrate for bacteria to proliferate. The complication of urine and urine 'scald' is also present in this location.

Macroscopic lesions.

The affected area is swollen, red and may be malodourous. The hair may be stained brown black and the skin hyperpigmented. An exudate may be present. Ulceration can also be present.

Microscopic lesions

Histopathology of the lesions indicates a hyperplastic dermatitis with a lichinoid infiltrate. In other words, the epidermis is hyperplastic with acanthosis and orthokeratotic or patchy parakeratotic hyperkeratosis. Superficial pustules and crusts may be present. Exocytosis of neutrophils may be present. Some cases will have erosion, and spongiosis may also be present. There is usually a band of inflammatory cells beneath the epithelium, and it is mostly plasma cells and lymphocytes with clusters of neutrophils. This band hugs the epithelium, but there is not an obvious attack on the basement membrane or basal layer. Single dead cells ('apoptotic" cells) and blurring of the basement membrane/basal layer is not a feature. In many cases, differentiation can only be made on clinical grounds including response to treatment for pyoderma.

Differential diagnosis

Perivulval dermatitis/mucocutaneous pyoderma should be differentiated from localized/discoid lupus erythematosis of the vulva, and other immune mediated diseases such as pemphigous, erythema multiforma/drug eruption and contact hypersensitivity.

 

Dorn AS. (1978) Biopsy in cases of canine vulvar-fold dermatitis & perivulvar pigmentation. Vet Med Small Anim Clin. 73(9):1147-1150.

Hammel SP, Bjorling DE. (2002) Results of vulvoplasty for treatment of recessed vulva in dogs. J Am Anim Hosp Assoc. 38(1): 79-83.

Lightner BA, McLoughlin MA, Chew DJ, Beardsley SM, Matthews HK. (2001) Episioplasty for the treatment of perivulvar dermatitis or recurrent urinary tract infections in dogs with excessive perivulvar skin folds: 31 cases (1983-2000). J Am Vet Med Assoc 219(11): 1577-1581

Immune mediated dermatitis

Differentiating pyoderma from immune mediated disease of the lupus type can be very difficult, or impossible. The main feature of the immune mediated diseases is death of basal cells and a cellular attack on components of the epithelium. If there is extensive distruction of the basal layer and infiltration of the epithelium with lymphocytes, and acantholysis, then immune mediated disease should be considered. Dermatopathology texts are particularly good in their differentiation of the various types. Sometimes the surgical pathologist can only suggest that the diseases be differentiated based on clinical grounds including the response to appropriate therapy.

Miscellaneous dermatoses

McEntee (1990) reports seeing Demodex mites in the labial skin.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic press p 205.

Neoplasia

The labial skin of the vulva develops a similar range of neoplastic disease to that of skin elsewhere. In the series of 99 vulvar and vaginal neoplasms by Thacher and Bradley (1983) 16 of the neoplasms were of the vulva, but the exact breakdown was not given. The following list is a compilation of those reported in the YagerBest database. Other reports are as indicated.

Round cell neoplasia

Mast cell tumour

Nine mast cell tumours are reported in the YagerBest database. Most were well differentiated tumours.

Transmissible venereal tumour

CTVT is found in the vestibule and may occur in the vulva. More details are given in the section on CTVT above. There is one recorded in the YagerBest database.

Plasmacytoma

There are 3 recorded in the YagerBest database.

Lymphoma

There is one recorded in the YagerBest database.

Histiocytoma

There is one recorded in the YagerBest database.

Mesenchymal neoplasia

Lipoleiomyoma

Squamous cell carcinoma

Thacher and Bradley (1983) report 99 cases of vulvar and vaginal tumours and found 4 squamous cell carcinomas.

There are 4 recorded in the YagerBest database.

Thacher C, Bradley RL (1983) Vulvar and vaginal tumors in the dog: a retrospective study. J Am Vet Med Assoc. 183(6): 690-692.

Transitional cell carcinoma/carcinoma of the canine vestibule

There is 4 anaplastic carcinomas recorded in the YagerBest database. They resemble carcinoma of the canine vestibule, which are discussed in diseases of the vagina and vestibule.

Sebaceous adenoma

There is one recorded in the YagerBest database.

Adenocarcinoma of the clitoris

Neihaus et al 2010 report on a dog with an adenocarcinoma identical to the apocrine adenocarcinoma of the anal sac that metastasised to the internal iliac lymph nodes and produced hypercalcemia.

Neihaus SA, Winter JE, Goring RL, Kennedy FA, Kiupel M. 2010: Primary Clitoral Adenocarcinoma With Secondary Hypercalcemia of Malignancy in a Dog. J Am Anim Hosp Assoc 2010; 46: 193-196 (http://www.jaaha.org/cgi/content/abstract/46/3/193?etoc)

Other neoplasia

Melanoma

Thacher and Bradley (1983) report 99 cases of vulvar and vaginal tumours and found 1 melanoma.

There is one recorded in the YagerBest database

Thacher C, Bradley RL (1983) Vulvar and vaginal tumors in the dog: a retrospective study. J Am Vet Med Assoc. 183(6): 690-692.

Miscellaneous

Vulval hyperplasia

The vulva changes with the reproductive cycle, enlarging with estrus and decreasing in size with anoestrus. It also tends to increase with older dogs that have had many litters (Bloom 1954).

 

Bloom F (1954) Pathology of the dog and cat - The genitourinary system, with clinical considerations. American Veterinary Publications, Inc, Evanston Illinois. p321

Varices

There is one recorded in the YagerBest database.

Calcinosis cutis of vulva only.

de Souza et al (2020) reported on a dog with calcinosis cutis of the vulva secondary to urinary incontinence and ectopic ureter.

de Souza LB, Dunn M, Doré M, Sauvé F. Vulvar calcinosis cutis in a female dog with urinary incontinence secondary to an ectopic ureter. Can Vet J. 2020; 61: 1295-1298.