Trichomoniasis occurs in approximately 3 million women annually. T. vaginalis, a small, mobile protozoan, is not part of normal vaginal flora. It is sexually transmitted and frequently occurs in the presence of other infections. It occurs in 13% to 25% of women attending gynecologic clinics and 7% to 35% of women attending clinics for sexually transmitted diseases, with a prevalence in the United States of just over 3%. It is more common in African Americans, clusters with other sexually transmitted diseases, and appears to be seen more frequently in older women. Although sexual contact is the primary mode of transmission, T. vaginalis can survive in hot tubs, tap water, and chlorinated swimming pools. Its sexual transmission is supported by the high prevalence (30% to 70%) in male partners of infected women and the improved cure rates of infected women whose partners are also treated. Fewer than 20% of men with T. vaginalis in their urine are symptomatic, and the infection may be self-limited; those that do have symptoms present with urethritis. A substantial percentage of women with trichomoniasis (10% to 50%) are also asymptomatic, but one third of asymptomatic infected women become symptomatic within 6 months.

Symptoms include a malodorous discharge, pruritus, dyspareunia (caused by vulvar edema), dysuria, and increased frequency of micturition. Physical examination generally reveals vulvar erythema and edema and, occasionally, characteristic petechial hemorrhages of the external genitalia and cervix (strawberry cervix is seen by the naked eye in only 1% to 2% of patients). Vaginal discharge may be minimal or abundant, frothy, and foul smelling. Signs and symptoms alone are not sufficiently helpful to make the definitive diagnosis.

Candidiasis is very common in the vagina, seen in up to half of asymptomatic women in some studies. In one private practice study, the incidence of candidiasis was 8.5%, and of these individuals, 25% were asymptomatic. In women with symptoms, complaints include vulvar pruritus and burning associated with a discharge. Symptoms are usually rather rapid in onset, classically occurring shortly before menstruation when the pH of the vagina falls. Up to one third of women are prone to vulvovaginal candidiasis after treatment with systemic antibiotics. Uncontrolled diabetes also predisposes to candidal infections, as does HIV, although usually at a more advanced stage with serious immune dysfunction. On physical examination, erythema, edema, and excoriation of the vulva are often prominent; sometimes there are pustules apparent on the skin. The discharge is typically thick, white, and adherent, often described as resembling cottage cheese.

Bacterial vaginosis, previously referred to as Gardnerella vaginitis or “nonspecific vaginitis,” can be asymptomatic in up to 50% of women. It is the most common clinical vaginitis and occurs when the normal lactobacillus, which produces hydrogen peroxide and keeps the vaginal pH acidic, is overgrown by other components of vaginal flora, typically anaerobes such as Gardnerella or Mycoplasma. Although it is not sexually transmitted, it is more common in women with multiple or new partners and also has a high prevalence in women who have sex with women. Other risk factors are douching, intrauterine device use, and smoking. The clinical picture tends to be one of mild discomfort without significant erythema or inflammation, although in 10% to 20% of cases, the vaginal burning and itching are more pronounced. Often, patients note a disagreeable “fishy” odor, particularly after unprotected intercourse. The discharge ranges from grayish to occasionally a yellow-green color. Wet mount of the discharge shows short, motile rods and characteristic clue cells (see Laboratory Evaluation).

A number of other infectious etiologies have been identified.

Group A streptococcus vaginitis, long recognized among prepubescent girls, has now been accepted as an uncommon but established etiology of vaginitis in adult women. It typically causes an acute onset of purulent discharge with vulvovaginal pain, burning, irritation, and pruritus, and responds quickly to oral penicillin or vaginal clindamycin.

Mucopurulent cervicitis caused by Chlamydia trachomatis or Neisseria gonorrhoeae (also covered in Chapter 137) is characterized by a thick, yellow-white discharge coming from the cervical os, which may be confused with a true vaginitis. Patients may complain of pruritus, purulent discharge, dysuria, or frequency and occasionally postcoital bleeding, although pain is usually absent unless upper tract infection is present. Generally, 10 or more leukocytes per microscopic field (high-power oil immersion) are seen on Gram stain examination. Erythema, friability, and ectocervical ulceration may occur.

In type 2 herpesvirus (see also Chapter 192), the infection can extend to the cervix in 75% of cases, producing ulceration, friability, and a grayish exudate in conjunction with a profuse watery discharge. In severe cases of condyloma acuminata, genital warts caused by papillomavirus, a profuse, irritating vaginal discharge may occur (see Chapter 194).

Atrophic vaginitis is the most common cause of vaginal discharge in older postmenopausal women and may also occur in younger woman with a hypoestrogenic state, such as postpartum or during lactation. Among postmenopausal women attending a vaginitis clinic in one study, a defined diagnosis of T. vaginalis, C. albicans, or bacterial vaginosis could be made in only one third of cases. Estrogen deficiency leads to thinning of the vaginal epithelium with a decrease in glycogen stores, contributing to a decline in Lactobacillus species and subsequent reduction in lactic acid production. The vaginal pH increases to up to 7.0, and vaginal flora changes from those listed to streptococci, coliform bacteria, and gut anaerobes; superinfection occurs more commonly in
this environment. Symptoms include vaginal and vulvar burning and soreness, occasional bleeding or itching, and dyspareunia. External burning on urination is sometimes noted, resulting from localized irritation of raw and inflamed mucosa rather than from infection of the urinary tract. Examination of the vaginal mucosa reveals a thin, erythematous surface and scant watery discharge.

A variety of other noninfectious processes occasionally result in vaginal discharge:

Cervical ectropion, found in 15% to 20% of healthy young women, occurs when columnar epithelium extends farther out on the exocervix, causing the cervix to appear granular and red. A large ectropion may result in a nonirritative mucoid vaginal discharge.

Cytolytic vaginosis results from an overgrowth of lactobacilli causing hyperacidity (pH 3.5 to 4.5) with cytolysis of vaginal epithelium and a frothy white discharge. Symptoms are similar to those of a candidal infection, including dyspareunia, vulvar pruritus, white vaginal discharge, and dysuria, often with a luteal phase increase in symptoms.

Desquamative inflammatory vaginitis, typically seen in perimenopausal women, is a rare and often chronic disorder, characterized by a change in vaginal bacterial composition, with replacement of lactobacilli by gram-positive cocci. It may cause purulent vaginal discharge, erythema, or vulvovaginal burning and irritation. Although responsive to clindamycin or hydrocortisone suppositories, it may require long-term maintenance therapy.

Lichen planus, an idiopathic inflammatory mucocutaneous disease, may cause a desquamative vaginitis. Certain collagen vascular diseases can also produce a type of vaginal inflammation and discharge.