Vaginitis: Common Causes and First-Line Treatments
The three most common infectious causes of vaginitis—bacterial vaginosis (40-50% of cases), vulvovaginal candidiasis (20-25%), and trichomoniasis (15-20%)—require prompt diagnosis using office-based testing (vaginal pH, wet mount, KOH prep) and targeted antimicrobial therapy, with metronidazole as first-line for bacterial vaginosis and trichomoniasis, and topical or oral azoles for candidiasis. 1, 2
Bacterial Vaginosis (Most Common)
Pathophysiology
- Bacterial vaginosis results from replacement of normal H₂O₂-producing Lactobacillus species with anaerobic overgrowth, including Gardnerella vaginalis, Prevotella, Mobiluncus, and Mycoplasma hominis. 1, 3
- This represents dysbiosis rather than a sexually transmitted infection, though multiple sexual partners increase risk. 1, 3
Diagnosis: Amsel Criteria (3 of 4 Required)
- Homogeneous, thin white or gray discharge 1, 4
- Vaginal pH > 4.5 1, 4
- Positive whiff test (fishy amine odor with 10% KOH) 1, 4
- Clue cells on wet mount microscopy 1, 4
First-Line Treatment
- Metronidazole 500 mg orally twice daily for 7 days is the CDC-recommended first-line therapy. 1, 4
- Alternative regimens include intravaginal metronidazole gel or intravaginal clindamycin cream. 4, 2
- Tinidazole is an alternative oral option for metronidazole-intolerant patients. 1
Critical Pitfalls
- Up to 50% of women with bacterial vaginosis are asymptomatic, so screening may be warranted before gynecologic procedures. 3
- Treating male partners does not prevent recurrence because this is not a classic STI. 1, 3
- Recurrence rates reach 50-80% within one year due to failure of Lactobacillus recolonization. 3
- In pregnancy, bacterial vaginosis is associated with preterm delivery and premature rupture of membranes; treatment with metronidazole is recommended. 4, 5
Vulvovaginal Candidiasis
Clinical Presentation
- Thick, white "cottage cheese-like" discharge with intense vulvar pruritus is characteristic. 1
- Vulvovaginal erythema and swelling are common findings. 4, 6
- Vaginal pH remains normal (3.8-4.5), distinguishing it from bacterial vaginosis and trichomoniasis. 1, 7
Diagnosis
- Microscopic examination with 10% KOH preparation revealing budding yeast or pseudohyphae confirms the diagnosis. 1, 7
- Culture with speciation is crucial for recurrent or complicated cases to identify non-albicans species (C. glabrata, C. tropicalis). 8, 2
First-Line Treatment
- Topical azole formulations (butoconazole, clotrimazole) or oral fluconazole are equally efficacious for uncomplicated infections. 4, 6
- In pregnancy, only topical azoles are recommended; oral fluconazole should be avoided. 4, 2
Management of Complicated Cases
- For Candida albicans recurrent infections, maintenance fluconazole therapy is effective. 8
- For non-albicans Candida (especially C. glabrata), vaginal boric acid therapy is the first-choice treatment. 8
Trichomoniasis
Clinical Presentation
- Frothy, greenish-yellow vaginal discharge with prominent vulvar itching is the hallmark. 1, 4
- "Strawberry cervix" (punctate hemorrhagic lesions) may be visible on speculum examination. 1
- Vaginal pH > 4.5 (often > 5.4) helps differentiate from candidiasis. 1, 7
Diagnosis
- Wet mount microscopy showing motile flagellated trichomonads is diagnostic but has 30-50% false-negative rate. 1
- Nucleic acid amplification testing (NAAT) is recommended due to superior sensitivity compared to wet mount. 4, 2
First-Line Treatment
- Metronidazole 2 g orally as a single dose is the CDC-recommended first-line therapy. 1, 4
- Tinidazole is an alternative for treatment failures or metronidazole-resistant cases. 1, 8
Critical Management Points
- All sexual partners must be treated simultaneously with the same single-dose regimen to prevent reinfection. 1, 4
- Patients should abstain from sexual intercourse until both partners complete therapy and are asymptomatic. 1, 4
- In pregnancy, the same 2 g single-dose metronidazole regimen is safe and recommended due to associations with preterm delivery and premature rupture of membranes. 1, 4
- Trichomoniasis increases HIV acquisition and transmission risk. 1
Essential Diagnostic Algorithm
Office-Based Testing (Required for All Cases)
- Vaginal pH testing differentiates causes: normal (3.8-4.5) suggests candidiasis; elevated (>4.5) suggests bacterial vaginosis or trichomoniasis. 1, 7
- Wet mount examination identifies motile trichomonads, clue cells (bacterial vaginosis), or budding yeast. 1, 4
- KOH preparation reveals pseudohyphae (candidiasis) and produces fishy odor (positive whiff test) in bacterial vaginosis. 1, 4
- Microscopic examination is essential; symptoms and physical examination alone are inadequate for accurate diagnosis. 1
Additional Testing When Indicated
- NAAT for Trichomonas vaginalis, Chlamydia trachomatis, and Neisseria gonorrhoeae should be performed in high-risk patients or when cervicitis is suspected. 4, 2
- Yeast culture with speciation is indicated for recurrent or treatment-refractory vulvovaginal candidiasis. 8, 2
Noninfectious Causes (5-10% of Cases)
Atrophic Vaginitis
- Results from estrogen deficiency and presents with vaginal dryness, irritation, and dyspareunia. 6, 7
- Topical or systemic estrogen therapy is effective treatment. 6, 2