Vaginal bleeding, which is a misused term, should instead be called vulvovaginal hemorrhagic discharge (VVHD). Indeed, VVHD refers to the clinical observation of blood leaking from the vulvar opening, while vaginal bleeding should theoretically refer only to a bleeding vagina.
VVHD is a normal physiologic observation during proestrus and estrus, which occurs on average every 7 months starting at puberty (range varying from 4 to more than 12 months). During the estrous cycle, bleeding is of uterine origin and is elicited by estrogens produced by the ovarian follicles (Figure 1). Proestrual and estrual bleeding will not be covered in detail here but will be included in the Diagnostic Tree.
Figure 1. (above) Proestrual vulvar bleeding in the bitch
Pathologic VVHD is complex and may find its origin from various parts of the female reproductive tract, from the vulva itself to the ovaries. In some instances the urinary tract may be involved or the bleeding may be caused by systemic problems such as coagulopathies (eg, disseminated intravascular coagulation). This article will cover only pathologic bleeding originating from the caudal reproductive tract even if the cause may stem from other areas.
The causes of VVHD vary greatly. Discharge originating from the vulva and the vagina can be traumatic, infectious, hormonal, or neoplastic. The discharge may be associated with an externally normal or abnormal vulva or the presence of lesions and/or protruding masses. Congenital abnormalities of the external reproductive tract (eg, recessed vulva) and vagina (eg, fibrous band, stricture, ectopic urethra, or hypolastic development) can often be primary causes of VVHD.
- Prepubertal vulvovaginitis is rarely infectious but generally caused by an underlying etiology (ie, congenital abnormalities/hormonal imbalance) that leads to irritation/inflammation and impairment of local immune defenses. Prepubertal vulvovaginitis is most often associated with mucous or mucopurulent discharge. However, hemorrhagic discharges are sometimes observed. Bacteria, if present, are generally nonspecific and of no real significance. Prepubertal vaginitis often resolves spontaneously after the first estrus. It should not be treated with antibiotics until the primary cause has been identified and cured. If clinical signs persist after primary treatment, antibiotics may be considered to control bacterial growth. However, antibiotic treatments will never cure the vaginitis if the primary cause is not corrected.