In vaginal hyperplasia, a proliferation of the vaginal mucosa, usually originating from the floor of the vagina anterior to the urethral orifice, occurs during proestrus and estrus as a result of estrogenic stimulation. Occasionally, the prolapse continues throughout pregnancy or recurs at parturition. The most common sign is a mass protruding from the vulva. Initially, the surface is smooth and glistening, but with prolonged exposure it becomes dry and fissures develop. A slight vaginal discharge may be present. Although the hyperplastic tissue originates near the urethral orifice, dysuria is uncommon. Vaginal hyperplasia interferes with copulation. Reluctance to breed or failure of intromission may be the only clinical sign if the hyperplastic tissue is contained within the vaginal vault. Vaginal hyperplasia resolves spontaneously as soon as estrogen declines.
The diagnosis is made by the history (stage of the estrous cycle) and examination of the vagina. Estrogenic stimulation could be confirmed by cornification of the vaginal epithelial cells, the presence of the characteristic serosanguineous estrous discharge, and the presence of estrous behavior. The differential diagnosis is vaginal neoplasia, which can be excluded by biopsy of the protruding tissue.
If the hyperplastic tissue is not causing problems, therapy is not indicated. However, if it protrudes from the vulva, it should be kept clean and moist and an antibiotic ointment applied. An Elizabethan collar may be necessary to prevent self-trauma. These animals may be bred by artificial insemination. The hyperplasia regresses as soon as the follicular phase of the estrous cycle has passed. Submucosal resection may be necessary if the mass is extremely large or if mucosal damage is extensive. Recurrence is common even after surgical resection. Vaginal hyperplasia resolves within days of removal of estrogen. Rarely, the hyperplasia recurs at parturition, presumably associated with a burst of estrogen. Ovariohysterectomy, the treatment of choice, permanently corrects this condition by removing the gonadal source of estrogen, thus preventing recurrence.