What is the most likely cause of a three‑month continuous whitish vaginal discharge that is especially noticeable at night?

Chronic White Vaginal Discharge for Three Months

The most likely cause of continuous white vaginal discharge over three months is vulvovaginal candidiasis (VVC), particularly if the discharge is thick and accompanied by pruritus, though bacterial vaginosis and physiologic discharge must be systematically excluded through point-of-care testing. 1, 2

Diagnostic Algorithm

Initial Point-of-Care Testing

Measure vaginal pH using narrow-range pH paper (4.0–6.0 range): 2

• pH < 4.5 strongly suggests vulvovaginal candidiasis or physiologic discharge 1, 2
• pH > 4.5 indicates bacterial vaginosis or trichomoniasis 2, 3

Perform microscopy on two preparations: 2, 3

• Saline wet mount: Look for clue cells (bacterial vaginosis) or motile trichomonads (trichomoniasis—though sensitivity is only 40–80%) 2, 4
• 10% KOH preparation: Examine for budding yeast or pseudohyphae to confirm candidiasis 1, 2, 3

Perform the whiff test: Add 10% KOH to discharge; a fishy odor indicates bacterial vaginosis or trichomoniasis, while absence of odor supports candidiasis 2, 3

Interpretation Based on Findings

If pH < 4.5, thick white "cottage cheese-like" discharge, no odor, and yeast/pseudohyphae on KOH:

• Diagnosis is vulvovaginal candidiasis 1, 2
• The three-month duration suggests either chronic/recurrent VVC (≥4 episodes per year) or persistent infection 1, 5

If pH > 4.5, thin gray-white homogeneous discharge, fishy odor, and clue cells:

• Diagnosis is bacterial vaginosis 2, 3
• Recurrent bacterial vaginosis is common and requires maintenance therapy 5

If all testing is negative with pH < 4.5 and clear-to-white discharge:

• Likely physiologic discharge 2, 3
• Reassurance is appropriate; no treatment needed 2

Treatment Recommendations

For Vulvovaginal Candidiasis (Most Likely Given "White Discharge")

For initial treatment of uncomplicated VVC: 1

• Single oral dose of fluconazole 150 mg is the recommended first-line therapy 1
• Alternative: Topical azole therapy for 7 days (clotrimazole 1% cream 5g intravaginally or miconazole 2% cream) 1, 3

For chronic/recurrent VVC (≥4 episodes per year, which three months of symptoms may represent): 1, 5

• Induction therapy: 10–14 days of topical azole OR fluconazole 150 mg on days 1,4, and 7 1
• Maintenance therapy: Fluconazole 150 mg once weekly for 6 months 1, 6
• This achieves >90% response rates in preventing recurrence 1

Critical consideration for non-albicans Candida (if culture reveals C. glabrata): 5

• Boric acid 600 mg intravaginal gelatin capsule daily for 14 days is first-line for azole-resistant species 1, 5
• Azole therapy frequently fails for C. glabrata infections 1

For Bacterial Vaginosis (If Diagnosed)

First-line treatment: 2, 3

• Metronidazole 500 mg orally twice daily for 7 days achieves ~95% cure rates 3
• Alternative: Metronidazole gel 0.75% intravaginally or clindamycin cream 3

For recurrent bacterial vaginosis: 5

• Maintenance therapy is often required after initial treatment 5

For Physiologic Discharge

No treatment is indicated 2, 3

• Reassurance that clear-to-white, odorless discharge with pH < 4.5 and normal microscopy is physiologic 2

Critical Pitfalls to Avoid

Never diagnose based on discharge appearance alone: Clinical characteristics are unreliable for distinguishing causes; pH testing and microscopy are essential 2

Do not assume all white discharge is candidiasis: Bacterial vaginosis can present with thin white-gray discharge, and physiologic discharge is also white 2, 3, 4

Obtain yeast culture with speciation if microscopy is negative but symptoms persist: Microscopy detects yeast in only 50–70% of candidiasis cases 4, 5

Consider NAAT testing for Trichomonas vaginalis if pH > 4.5 and wet mount is negative: Wet mount sensitivity is only 40–80% 2, 3

Avoid empiric antifungal therapy without confirmed diagnosis: This contributes to inappropriate antibiotic use and increasing azole resistance 2, 7

Partner treatment is NOT required for candidiasis or bacterial vaginosis: Only sexually transmitted infections (trichomoniasis, gonorrhea, chlamydia) require partner therapy 3, 8

Special Considerations for Nighttime Symptoms

The patient notes symptoms are worse "during night," which may reflect:

• Increased awareness of discharge when lying down (physiologic) 2
• Nocturnal pruritus from candidiasis disrupting sleep 1
• This symptom pattern does not change the diagnostic algorithm but supports obtaining definitive testing rather than empiric treatment 2