Vaginal hyperplasia is an exaggerated swelling of the vaginal lining that occurs during proestrus and estrus in response to the influence of estrogen. When the swollen vaginal mucosa can no longer be contained within the vagina, it bulges out through the vaginal lips. The principal sign is the protrusion of a tongue-shaped mass through the vulva. Other signs include painful urination and excessive licking at the vulva.
The protruding mass prevents mating. Vaginal hyperplasia occurs most often in young bitches of the larger breeds, particularly Boxers and St. Bernards.
Severe hyperplasia may progress to prolapse. In a dog with vaginal prolapse, the apex of the vagina drops out through the vulva, resembling a donut-shaped mass. This can be mistaken for a vaginal tumor.
Vaginal prolapse can also be caused by prolonged straining, such as that associated with anorectal obstructions and difficult labor and delivery. Another cause of vaginal prolapse is forcefully separating dogs during the tie (see Prolonged Tie).
Treatment: Vaginal hyperplasia subsides during diestrus but tends to recur with each new heat cycle. For mild hyperplasia, no treatment is necessary other than to keep the vaginal membranes clean and well lubricated with antibiotic ointment to prevent drying.
If the bitch is to be bred, artificial insemination is the method of choice. If breeding is not intended, the bitch should be spayed. This cures the problem. For severe hyperplasia or vaginal prolapse, it may be possible for your veterinarian to push the everted tissue back into the vagina and hold it in place with sutures until it regresses during diestrus. Surgical excision may be required to remove devitalized tissue and prevent hyperplasia during future cycles.