How should I evaluate and manage a patient presenting with white vaginal discharge?

Evaluation and Management of White Vaginal Discharge

Immediate Diagnostic Workup

Perform point-of-care testing with vaginal pH measurement, saline wet mount microscopy, and 10% KOH preparation to differentiate between the three most common causes: bacterial vaginosis, vulvovaginal candidiasis, and trichomoniasis. 1

Step 1: Measure Vaginal pH

• Use narrow-range pH paper as the critical first step 1
• pH ≤4.5 indicates vulvovaginal candidiasis 1, 2
• pH >4.5 suggests bacterial vaginosis or trichomoniasis 3, 1

Step 2: Prepare Microscopy Slides

• Dilute vaginal discharge sample in 1-2 drops of 0.9% normal saline on one slide 3
• Place 1-2 drops of discharge in 10% KOH solution on a second slide 3
• Perform the "whiff test" immediately when applying KOH—a fishy odor indicates bacterial vaginosis or trichomoniasis 3

Step 3: Microscopic Examination

• Saline wet mount identifies motile trichomonads (trichomoniasis) or clue cells (bacterial vaginosis) 3, 1
• KOH preparation visualizes yeast or pseudohyphae confirming candidiasis 3, 1, 2

Diagnosis and Treatment by Specific Condition

Bacterial Vaginosis (Most Common Cause)

Bacterial vaginosis is the most prevalent cause of vaginal discharge, characterized by replacement of normal H2O2-producing Lactobacillus with high concentrations of anaerobic bacteria. 3

Diagnostic Criteria (Amsel Criteria - Need 3 of 4):

• Homogeneous, white, noninflammatory discharge that smoothly coats vaginal walls 3
• Clue cells on microscopic examination 3
• Vaginal pH >4.5 3
• Positive whiff test (fishy odor with KOH) 3

Treatment:

• First-line: Metronidazole 500 mg orally twice daily for 7 days 3, 4, 5
• Alternative: Metronidazole 2 g orally single dose 3
• Alternative: Intravaginal metronidazole gel or clindamycin cream 3, 1
• Advise patients to avoid alcohol during treatment and for 24 hours after 3
• Do not treat male partners—this does not prevent recurrence 3, 4

Vulvovaginal Candidiasis

Candidiasis presents with white, thick "cottage cheese" discharge, normal pH (≤4.5), and intense vulvar itching and burning. 2

Diagnostic Confirmation:

• Yeast or pseudohyphae visible on KOH preparation 1, 2
• Normal vaginal pH (≤4.5) 1, 2
• Erythema and swelling of vulvovaginal tissues 2

Treatment for Uncomplicated Cases:

• Oral fluconazole 150 mg single dose 1, 6
• Alternative: Topical azoles (clotrimazole, miconazole, terconazole) for 1-7 days 1, 2

Treatment for Complicated/Recurrent Cases (≥4 episodes/year):

• Initial: Topical azole therapy for 7-14 days OR fluconazole 150 mg every 72 hours for 3 doses 2, 4
• Maintenance: Fluconazole 150 mg weekly for 6 months 2, 4

Trichomoniasis

Trichomoniasis causes yellow-green, frothy, malodorous discharge with vulvar irritation. 1, 2

Diagnostic Confirmation:

• Motile trichomonads on saline wet mount 3, 1
• Vaginal pH >4.5 1
• Culture or NAAT for confirmation if wet mount negative 1

Treatment:

• Metronidazole 2 g orally single dose 1, 4
• Alternative: Metronidazole 500 mg twice daily for 7 days 1
• Treat sexual partners simultaneously to prevent reinfection 1, 2

Special Population Considerations

Pregnant Women:

• Treat all symptomatic pregnant women with bacterial vaginosis or trichomoniasis to reduce risk of preterm labor and premature rupture of membranes 1
• For candidiasis in pregnancy: Use ONLY 7-day topical azole therapy—oral fluconazole is contraindicated 1, 2, 4
• For bacterial vaginosis: Oral metronidazole 500 mg twice daily for 7 days is safe 4

HIV-Infected/Immunocompromised Women:

• Treat with identical regimens as immunocompetent women—no modification needed 1, 2

High-Risk Pregnant Women (Prior Preterm Delivery):

• Consider treating asymptomatic bacterial vaginosis to reduce prematurity risk 3

Critical Pitfalls to Avoid

• Never treat based solely on microscopic findings without symptoms—10-20% of women normally harbor Candida without infection 2
• Do not culture Gardnerella vaginalis for diagnosis—it lacks specificity and is present in 50% of normal women 3
• Avoid self-medication recommendations except for women previously diagnosed with candidiasis experiencing identical recurrent symptoms 2, 4
• Do not use vaginal douching—it disrupts normal flora and increases infection risk 4
• Metronidazole treatment can precipitate vulvovaginal candidiasis in 12.5-30% of patients—consider concurrent antifungal therapy when treating bacterial vaginosis in symptomatic women 2

When Laboratory Testing Fails

Laboratory testing fails to identify the cause among a substantial minority of women. 3 In these cases:

• Consider non-infectious causes: mechanical irritation, chemical irritation, allergic reaction, or atrophic vaginitis 3
• Look for objective signs of vulvar inflammation with minimal discharge 3
• Consider culture for Trichomonas (more sensitive than microscopy) 3

Follow-Up Recommendations

• Patients should return only if symptoms persist or recur within two months 4
• Repeat wet mount examination if symptoms develop after initial negative evaluation 2