What is the differential diagnosis and recommended management for vaginal itching?

Vaginal Itching: Differential Diagnosis and Management

Immediate Diagnostic Approach

Vaginal itching most commonly indicates vulvovaginal candidiasis (VVC), but requires laboratory confirmation through vaginal pH testing, wet mount microscopy, and KOH preparation before initiating treatment. 1

Essential Office-Based Testing

• Measure vaginal pH immediately: pH ≤4.5 suggests VVC, while pH >4.5 indicates bacterial vaginosis (BV) or trichomoniasis 1, 2
• Perform wet mount microscopy in saline: Look for motile trichomonads (trichomoniasis), clue cells (BV), or increased leukocytes 1, 2
• Prepare KOH slide: Visualize budding yeast or pseudohyphae for VVC diagnosis; KOH disrupts cellular debris to improve yeast visualization 3
• Conduct whiff test: Fishy odor after adding KOH indicates BV, not VVC 1, 2

Critical caveat: Symptoms alone cannot reliably distinguish between causes—approximately 10-20% of women harbor Candida without symptoms, so treatment must be based on both clinical presentation and laboratory findings 1, 4

Primary Differential Diagnoses

Vulvovaginal Candidiasis (Most Likely with Isolated Itching)

• Presentation: Intense vulvar pruritus as the most specific symptom, often with thick white "cottage cheese" discharge, vaginal soreness, dyspareunia, and external dysuria 3, 4, 2
• Diagnostic findings: Normal vaginal pH (<4.5), yeast or pseudohyphae on microscopy, no fishy odor 3, 1
• Treatment for uncomplicated VVC: Short-course topical azoles (1-3 days) or single-dose oral fluconazole 150 mg achieve 80-90% cure rates 3, 5
  • Intravaginal options: Clotrimazole 1% cream for 7-14 days, clotrimazole 100 mg tablet for 7 days, or butoconazole 2% cream for 3 days 3
  • Pregnancy exception: Use only topical azoles; avoid oral fluconazole due to association with spontaneous abortion and congenital defects 3, 4

Bacterial Vaginosis (Minimal Itching, Prominent Odor)

• Presentation: Malodorous discharge (fishy smell) with minimal vulvar irritation or itching; homogeneous thin white-gray discharge 3, 2
• Diagnostic findings: Vaginal pH >4.5, clue cells on microscopy, positive whiff test, absence of inflammation 1, 2
• Treatment: Metronidazole 500 mg orally twice daily for 7 days, or metronidazole 0.75% gel intravaginally for 5 days, or clindamycin 2% cream intravaginally for 7 days 2, 5
• Partner management not required: BV represents vaginal dysbiosis, not simple sexual transmission 2

Trichomoniasis (Itching with Profuse Discharge)

• Presentation: Profuse yellow-green frothy discharge, vulvar irritation, dysuria, and itching; "strawberry cervix" may be visible 1, 2
• Diagnostic findings: Vaginal pH >4.5, motile trichomonads on wet mount (though sensitivity only 50-70%), positive whiff test possible 2, 5
• Treatment: Metronidazole 2 g orally as single dose for both patient and all sexual partners simultaneously 3, 2, 5
• Sexual abstinence required: Until both patient and partner complete therapy and are asymptomatic 3, 2
• Important association: Linked to increased HIV transmission risk and adverse pregnancy outcomes including preterm delivery 3, 2

Contact Dermatitis/Irritant Vaginitis (External Inflammation)

• Presentation: Vulvar inflammation with minimal vaginal discharge, caused by mechanical, chemical, or allergic irritation 3, 1
• Diagnostic findings: External vulvar erythema without vaginal pathogens on microscopy 3
• Management: Identify and eliminate irritant; consider barrier restoration and topical corticosteroids for severe cases 1

Diagnostic Algorithm Summary

1. First step: Obtain vaginal pH—this single test narrows the differential significantly 1, 2

   • pH ≤4.5 → VVC most likely
   • pH >4.5 → BV or trichomoniasis

2. Second step: Perform wet mount microscopy 1, 2

   • Yeast/pseudohyphae → VVC
   • Clue cells → BV
   • Motile trichomonads → Trichomoniasis

3. Third step: KOH preparation and whiff test 1, 2

   • Positive whiff → BV (occasionally trichomoniasis)
   • Improved yeast visualization → VVC

4. If microscopy negative but symptoms persist: Consider culture for VVC (more sensitive than microscopy) or nucleic acid amplification testing for trichomoniasis 3, 5

Common Pitfalls to Avoid

• Do not treat based on symptoms alone: Laboratory confirmation prevents misdiagnosis and inappropriate antibiotic use 1
• Do not assume single infection: Mixed infections occur commonly and may require combination therapy 1
• Do not treat asymptomatic Candida colonization: 10-20% of healthy women harbor yeast without disease 1, 4
• Do not forget partner treatment for trichomoniasis: Failure to treat partners leads to reinfection 3, 2
• Do not use oral fluconazole in pregnancy: Teratogenic risk requires topical azoles only 3, 4

Special Populations

HIV-Infected Women

• VVC may be more severe with lower CD4+ counts, but treatment regimens remain identical to HIV-negative women 3, 4
• Trichomoniasis increases viral shedding and HIV transmission risk 3

Recurrent VVC (≥4 Episodes/Year)

• Requires different management approach with extended induction therapy followed by maintenance suppression 4
• Consider culture to identify non-albicans species requiring alternative treatment 3