Treatment of Vaginal Discharge with Fishy Odor and Itch
The combination of fishy odor and itch most likely represents bacterial vaginosis (BV) with concurrent vulvovaginal candidiasis, and you should treat with metronidazole 500 mg orally twice daily for 7 days plus fluconazole 150 mg as a single oral dose. 1, 2
Diagnostic Confirmation
Before initiating treatment, confirm the diagnosis using point-of-care testing:
Measure vaginal pH using narrow-range pH paper—BV typically shows pH >4.5, while candidiasis shows pH ≤4.5. 3, 2 The presence of both conditions may show elevated pH.
Perform the whiff test by adding 10% KOH to vaginal discharge—a fishy amine odor indicates BV. 3
Examine wet mount microscopy with saline preparation to identify clue cells (epithelial cells covered with bacteria) diagnostic of BV, and KOH preparation to identify yeast or pseudohyphae indicating candidiasis. 3, 2
Look for clinical signs: BV presents with homogeneous white-grey discharge coating vaginal walls, while candidiasis causes vulvar erythema, edema, and thick white "cottage cheese" discharge. 3, 4
The fishy odor strongly suggests BV, while itching (pruritus) is the hallmark of candidiasis—this dual presentation indicates coinfection. 5, 4
First-Line Treatment Regimen
For bacterial vaginosis:
Metronidazole 500 mg orally twice daily for 7 days is the CDC-recommended first-line treatment. 1, 2
Alternative if metronidazole is contraindicated: clindamycin 2% vaginal cream. 1
For vulvovaginal candidiasis:
Fluconazole 150 mg as a single oral dose is highly effective, with 55% therapeutic cure rates (complete symptom resolution plus negative culture). 2, 6
Alternative topical options include clotrimazole, miconazole, or terconazole intravaginally for 7 days if oral therapy is contraindicated. 2
Critical Patient Instructions
Alcohol avoidance is mandatory: The patient must avoid all alcohol during metronidazole treatment and for 24 hours after completion to prevent disulfiram-like reactions (severe nausea, vomiting, flushing). 1
Contraception during treatment: Women of childbearing potential should use effective contraception during fluconazole treatment and for 1 week after the final dose. 6
Complete the full course: Even if symptoms resolve early, completing the 7-day metronidazole course reduces recurrence risk. 1
When to Consider Alternative Diagnoses
If symptoms persist after appropriate treatment:
Reconsider trichomoniasis, which also causes fishy odor and elevated pH but includes frothy yellow-green discharge and "strawberry cervix." Wet mount microscopy misses trichomoniasis 30-50% of the time, so nucleic acid amplification testing may be needed. 3, 5
Evaluate for mixed infections: Laboratory testing fails to identify a cause in a substantial minority of women with vaginal complaints. 3, 7
Consider non-infectious causes if all testing is negative, including atrophic vaginitis (postmenopausal), irritant/allergic vaginitis, or desquamative inflammatory vaginitis. 5, 8
Follow-Up Recommendations
No routine follow-up is needed if symptoms completely resolve after treatment. 1, 2
Return for persistent or recurrent symptoms within 2 months, which may indicate treatment failure or reinfection requiring extended therapy or alternative agents. 1, 2
For recurrent BV (≥3 episodes per year), consider extended suppressive therapy after initial treatment, though specific regimens require consultation with current CDC guidelines. 8, 9, 10
Common Pitfalls to Avoid
Do not treat based on symptoms alone—the combination of fishy odor and itch could represent BV alone (with irritation from discharge), candidiasis alone (with secondary bacterial overgrowth), or true coinfection. Confirm with pH and microscopy. 3, 5
Do not use metronidazole as a single 2-gram dose for BV—this regimen is for trichomoniasis only. BV requires the 7-day course for optimal cure rates. 1, 5
Do not treat male partners for BV—partner treatment does not reduce recurrence rates and is not recommended. 3, 1
Avoid empiric treatment without considering pregnancy status—pregnant women with BV require treatment due to associations with preterm birth and should have follow-up evaluation one month after treatment to verify cure. 1