What is the cause and treatment of yellowish green vaginal discharge?

Yellowish-Green Vaginal Discharge: Diagnosis and Treatment

Yellowish-green vaginal discharge is most commonly caused by trichomoniasis, a sexually transmitted infection caused by Trichomonas vaginalis, and should be treated with metronidazole 2 g orally as a single dose, with mandatory simultaneous treatment of all sexual partners. 1

Diagnostic Confirmation

The diagnosis requires specific laboratory testing to distinguish trichomoniasis from other causes:

• Perform wet mount microscopy to identify motile trichomonads, which is the classic presentation of greenish discharge 1
• Measure vaginal pH using narrow-range pH paper; pH >4.5 supports trichomoniasis or bacterial vaginosis, while pH ≤4.5 suggests candidiasis 1
• Conduct a whiff test by applying 10% KOH to the discharge; a fishy odor indicates bacterial vaginosis or trichomoniasis 2, 1
• Culture for T. vaginalis is more sensitive than microscopic examination if initial wet mount is negative but clinical suspicion remains high 2

First-Line Treatment for Trichomoniasis

Once trichomoniasis is confirmed, treatment is straightforward:

• Metronidazole 2 g orally as a single dose is the standard treatment, achieving cure rates of 90-95% 2, 1, 3
• Alternative regimen: Metronidazole 500 mg orally twice daily for 7 days if single-dose therapy fails or is not tolerated 1
• Instruct patients to avoid alcohol during metronidazole treatment and for 24 hours after completion due to disulfiram-like reactions 1

Critical Management: Partner Treatment is Mandatory

The most common pitfall is failing to treat sexual partners simultaneously, which leads to reinfection:

• All sexual partners must be treated concurrently, even if asymptomatic, as most infected men have no symptoms 2, 1
• Patients must abstain from sexual intercourse until both patient and all partner(s) complete treatment and are asymptomatic 1
• Negative cultures in male partners cannot be relied upon to rule out infection, as isolating the organism from asymptomatic male carriers is difficult 3
• Reinfection is common when partners are not treated, and this is the primary cause of treatment failure 2, 3

Special Populations

Treatment modifications apply to specific patient groups:

• Pregnant women who are symptomatic should be treated with oral metronidazole to relieve symptoms, as trichomoniasis is associated with premature rupture of membranes, preterm delivery, and low birth weight 2, 1
• HIV-infected patients should receive the same treatment regimen as HIV-negative patients 2, 1

Alternative Diagnoses to Consider

If the presentation differs from classic trichomoniasis, consider these alternatives:

• Bacterial vaginosis: If greenish discharge is accompanied by a fishy odor and pH >4.5 but no motile trichomonads are seen, treat with metronidazole 500 mg orally twice daily for 7 days or intravaginal metronidazole gel 0.75% once daily for 5 days 1
• Vulvovaginal candidiasis: If greenish discharge is accompanied by pruritus and pH ≤4.5, confirm with KOH preparation showing yeast/pseudohyphae, then treat with fluconazole 150 mg orally as a single dose or topical azoles 1
• Cervicitis from Chlamydia or Gonorrhea: May present with vaginal discharge and requires nucleic acid amplification testing and appropriate antibiotic coverage 2, 4

Follow-Up Strategy

Follow-up is unnecessary for patients who become asymptomatic after treatment 1

However, patients should return for re-evaluation if:

• Symptoms persist or recur within 2 months, which may indicate treatment failure, reinfection from an untreated partner, or an alternative diagnosis 1
• Pregnant women require follow-up evaluation one month after treatment completion to verify therapeutic effectiveness due to the risk of adverse pregnancy outcomes 2

Common Pitfalls to Avoid

• Do not treat empirically without confirming diagnosis, as symptoms alone cannot distinguish between causes reliably 2, 5
• Do not overlook partner treatment, as this is the primary cause of recurrent infection 2, 3
• Do not assume all discharge is infectious; mechanical or chemical irritation from soaps, douches, or hygiene products may contribute to symptoms 2, 6
• Do not rely on symptom resolution alone in pregnant women; objective follow-up testing is required 2