Vaginitis for USMLE Step 1
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Vaginitis for the USMLE Step 1 Exam
Definition and Classification
- Definition
- Vaginitis is an inflammation or infection of the vaginal mucosa, leading to discharge, pruritus, odor, or pain.
- Primary causes include:
- Bacterial Vaginosis (BV): Overgrowth of anaerobic bacteria.
- Vulvovaginal Candidiasis (VVC): Fungal infection, usually from Candida albicans.
- Trichomoniasis: Sexually transmitted infection caused by Trichomonas vaginalis.
- Epidemiology
- BV and VVC are common in reproductive-age women, while trichomoniasis is the most widespread non-viral STI globally.
Pathophysiology
- Bacterial Vaginosis (BV):
- Caused by a reduction in lactobacilli, which normally maintain a low vaginal pH through lactic acid production.
- Loss of acidity allows overgrowth of anaerobes such as Gardnerella vaginalis, Mycoplasma, Mobiluncus, and Prevotella.
- BV is associated with sexual activity but is not classified as an STI.
- Vulvovaginal Candidiasis (VVC):
- Overgrowth of Candida species, commonly C. albicans, occurs due to an imbalance in the vaginal flora.
- Risk factors include antibiotic use, diabetes, immunosuppression, and high estrogen levels (e.g., pregnancy, oral contraceptives).
- Trichomoniasis:
- Caused by Trichomonas vaginalis, a flagellated protozoan transmitted through sexual contact.
- Reinfection rates are high due to frequent asymptomatic cases and untreated partners.
Clinical Manifestations
- Bacterial Vaginosis (BV):
- Thin, gray-white discharge with a fishy odor, often more noticeable after intercourse.
- Typically mild or asymptomatic but may present with slight itching or irritation.
- Vulvovaginal Candidiasis (VVC):
- Thick, white, “cottage cheese” discharge without a strong odor.
- Intense pruritus, vulvar erythema, swelling, and sometimes dysuria or dyspareunia.
- Trichomoniasis:
- Frothy, yellow-green discharge with a foul odor.
- Vaginal itching, erythema, and, in some cases, “strawberry cervix” (punctate hemorrhages on the cervix).
Diagnosis
- Microscopy (Wet Mount):
- BV: Presence of clue cells (epithelial cells coated with bacteria) and a positive “whiff” test (fishy odor when KOH is added).
- VVC: KOH preparation shows pseudohyphae and budding yeast.
- Trichomoniasis: Motile trichomonads are observed on a saline wet mount.
- pH Testing:
- BV and Trichomoniasis: Vaginal pH typically >4.5.
- VVC: Vaginal pH is usually normal (≤4.5).
- Additional Testing:
- NAAT (Nucleic Acid Amplification Tests): Highly sensitive for detecting Trichomonas vaginalis.
- Culture: Sometimes used for recurrent VVC to confirm Candida species.
Management
- Bacterial Vaginosis (BV):
- First-Line Therapy:
- Metronidazole 500 mg orally twice daily for 7 days or metronidazole gel 0.75% intravaginally for 5 days.
- Clindamycin 2% cream intravaginally for 7 days.
- Recurrent BV: Metronidazole gel twice weekly for up to 4-6 months may help reduce recurrence.
- Vulvovaginal Candidiasis (VVC):
- Uncomplicated VVC: Topical azoles (clotrimazole, miconazole) or single-dose fluconazole 150 mg orally.
- Complicated VVC: Prolonged treatment with topical azoles for 7-14 days or fluconazole 150 mg every 3 days for 3 doses.
- Recurrent VVC: Induction therapy with fluconazole followed by weekly maintenance therapy for 6 months.
- Trichomoniasis:
- First-Line Therapy: Metronidazole 2 g orally in a single dose or 500 mg twice daily for 7 days.
- Partner Treatment: Essential to prevent reinfection.
- Test of Cure: Recommended after 3 months due to high reinfection rates.
Key Points
- Vaginitis commonly results from BV, VVC, or trichomoniasis, each with unique causes and presentations.
- Symptoms:
- BV: Thin, gray-white discharge with a fishy odor; pH >4.5.
- VVC: Thick, white “cottage cheese” discharge; intense pruritus; pH ≤4.5.
- Trichomoniasis: Frothy, yellow-green discharge with foul odor; pH >4.5.
- Diagnosis:
- Wet mount microscopy, pH testing, and NAATs are key diagnostic tools.
- Treatment:
- BV: Metronidazole or clindamycin.
- VVC: Topical azoles or oral fluconazole for uncomplicated cases; extended treatment for complicated or recurrent cases.
- Trichomoniasis: Single-dose metronidazole; partner treatment required.
- Complications:
- BV and trichomoniasis are associated with higher risks for PID, preterm birth, and increased susceptibility to STIs.