Prolonged Estradiol Exposure and Stromal Fibrosis Influence Treatment Response in Canine Vaginal Hyperplasia

Vaginal hyperplasia is an estrogen-dependent condition commonly observed in bitches during proestrus and estrus. To evaluate how the duration of vaginal hyperplasia in bitches affects its treatment outcome.

The present clinical study reports 11 cases of vaginal hyperplasia in bitches presented to the Teaching Veterinary Clinical Complex, Bihar Veterinary College, Patna, over a one-year period. Diagnosis was based on clinical examination, vaginal cytology, serum estradiol assay and ultrasonography. Blood parameters (CBC and serum biochemistry) were within normal ranges in all cases. Treatment groups were divided into medical management with human chorionic gonadotropin (hCG, 500 IU intramuscularly at alternate-day intervals for three doses; n = 5) and surgical management by ovariohysterectomy (OVH; n = 6). Clinical outcomes were monitored by the regression of prolapse and changes in serum estradiol concentration.

OVH resulted in a marked reduction of serum estradiol (from 49.5 pg/mL to 12.5 pg/mL), with resolution of hyperplasia in 67% of cases. hCG treatment achieved clinical regression in 60% of cases, consistent with previous reports of variable efficacy. When hyperplasia lasted for 10 days or more, the incidence of fibrosis was 80%, compared to only 20% when it lasted for less than 10 days. Histopathological evaluation revealed stromal fibrosis in non-responsive instances, particularly when hyperplasia persisted for more than 10 days, indicating a strong correlation between prolonged estradiol exposure and the development of fibrotic changes. These findings suggest that while hCG may provide limited therapeutic benefit in field conditions, ovariohysterectomy remains the definitive treatment. Furthermore, the duration of estrogenic stimulation appears to influence stromal remodelling and may predict therapeutic outcomes.