What are the common causes of vaginitis and how do you tell them apart?
A healthy vagina is acidic (pH below 4.5) and dominated by hydrogen-peroxide and lactic-acid-producing Lactobacillus species. Vaginitis occurs when this ecosystem is disrupted. In practice, three conditions account for most infective discharge: bacterial vaginosis (BV), vulvovaginal candidiasis (VVC) and trichomoniasis. Two bedside tests — vaginal pH and the whiff test (10% KOH) — plus a wet mount separate them in minutes.
| Feature | Bacterial vaginosis | Vulvovaginal candidiasis | Trichomoniasis |
|---|---|---|---|
| Organism | Loss of lactobacilli; overgrowth of Gardnerella vaginalis and other anaerobes | Candida albicans (usually) | Trichomonas vaginalis (flagellate protozoan) |
| Transmission | Dysbiosis; linked to new/multiple partners, douching | Endogenous; not usually sexual | Sexually transmitted (commonest non-viral STI worldwide) |
| Discharge | Thin, homogeneous, milky, fishy odour | Thick, white, curdy (cottage-cheese-like) | Frothy, malodorous, yellow-green |
| Symptoms | Often no itching or inflammation | Pruritus, vulvar erythema, dysuria | Pruritus, dysuria, dyspareunia |
| Vaginal pH | > 4.5 | Normal (< 4.5) | > 4.5 |
| Whiff test (KOH) | Positive (fishy) | Negative | Not a defining feature |
| Microscopy | Clue cells; few WBCs; Gram stain: Nugent score | Budding yeast, hyphae, pseudohyphae (KOH prep) | Motile trichomonads; many WBCs |
| Cervix | Normal | Normal | Strawberry cervix (uncommon) |
How is bacterial vaginosis diagnosed — Amsel criteria and Nugent score?
BV is a vaginal dysbiosis: normal H2O2- and lactic-acid-producing lactobacilli are replaced by high concentrations of anaerobic bacteria including Gardnerella vaginalis. It was once attributed solely to Gardnerella, but is now regarded as a polymicrobial condition. Most women with BV are in fact asymptomatic.
| Criterion | Finding |
|---|---|
| 1 | Homogeneous, thin, milk-like discharge that smoothly coats the vaginal walls |
| 2 | Clue cells on microscopy (vaginal epithelial cells studded with adherent bacteria) |
| 3 | Vaginal fluid pH > 4.5 |
| 4 | Fishy odour before or after adding 10% KOH — the whiff test |
| Score | Interpretation |
|---|---|
| 0–3 | Lactobacillus-predominant normal flora |
| 4–6 | Intermediate flora (emergence of G. vaginalis) |
| 7–10 | Bacterial vaginosis |
How is bacterial vaginosis treated, and should the partner be treated?
| Category | Regimen |
|---|---|
| Recommended | Metronidazole 500 mg orally twice daily for 7 days |
| Recommended | Metronidazole gel 0.75%, one applicator (5 g) intravaginally once daily for 5 days |
| Recommended | Clindamycin cream 2%, one applicator (5 g) intravaginally at bedtime for 7 days |
| Alternative | Clindamycin 300 mg orally twice daily for 7 days; clindamycin ovules 100 mg intravaginally for 3 days; secnidazole 2 g oral granules single dose; tinidazole 2 g daily for 2 days or 1 g daily for 5 days |
| Recurrent BV | Oral metronidazole or tinidazole 500 mg twice daily for 7 days, then intravaginal boric acid 600 mg daily for 21 days, then metronidazole gel twice weekly for 4–6 months |
- Pregnancy: treat all symptomatic pregnant women — symptomatic BV is associated with premature rupture of membranes, preterm birth, intra-amniotic infection and postpartum endometritis. Any recommended regimen may be used, plus oral clindamycin or ovules.
- Condoms: clindamycin cream is oil based and can weaken latex condoms and diaphragms for 5 days after use.
- Alcohol: CDC notes no convincing evidence of a disulfiram-like reaction between alcohol and metronidazole, although many older texts still advise avoidance.
- Partner: older trials found that a woman's response and relapse risk are not affected by treating her male partner, and CDC does not recommend routine partner treatment. The 2025 ACOG advice summarised in StatPearls is to consider partner treatment in recurrent or symptomatic cases. Exam default: no routine partner treatment in BV.
- Douching may increase relapse and has no role in treatment.
What are the features and treatment of vulvovaginal candidiasis?
VVC is usually caused by *Candida albicans*. The classic picture is vulvar pruritus, pain, swelling and redness with a thick, white, curdy discharge, edema and fissures or excoriations. The vaginal pH is normal (below 4.5) and the whiff test is negative. Diagnosis is by a wet preparation (saline or 10% KOH) showing budding yeast, hyphae or pseudohyphae; culture is the reference standard. KOH disrupts cellular debris so yeast and mycelia are easier to see.
Risk factors: raised oestrogen (pregnancy, obesity, oestrogen use), diabetes mellitus, immunosuppression (HIV, chemotherapy, corticosteroids, transplant) and broad-spectrum antibiotic use. Recurrent disease can be triggered by antibiotics, sexual activity or diet.
| Type | Definition | Treatment |
|---|---|---|
| Uncomplicated | Sporadic or infrequent, mild-to-moderate, likely C. albicans, non-immunocompromised | Short-course topical azoles (single dose to 7 days) or fluconazole 150 mg orally once |
| Complicated | Recurrent, severe, non-albicans, or in diabetes/immunosuppression | Topical azole for 7–14 days, or fluconazole 150 mg two doses 72 hours apart |
| Recurrent | Persistent or recurrent episodes | Induction (7–14 days topical, or fluconazole on days 1, 4, 7) then weekly fluconazole for 6 months |
| Pregnancy | — | Only topical azoles for 7 days |
What is trichomoniasis and how is it diagnosed and treated?
Trichomonas vaginalis is a unicellular motile flagellate protozoan that lives in the lower genital tract of women and the urethra and prostate of men. It is the most common non-viral sexually transmitted infection worldwide and is often asymptomatic. Women may have frothy, malodorous, yellow-green discharge, dyspareunia, dysuria and vulvar itching. A strawberry cervix — punctate haemorrhages on the cervix or vaginal mucosa — is classic but uncommon (about 2% of women). Vaginal pH exceeds 4.5.
- Diagnosis: microscopy (motile trichomonads on a wet mount — specificity above 99% but sensitivity only about 60%), a rapid antigen test, or a nucleic acid amplification test (NAAT), which is the preferred method.
- Treatment (women): metronidazole 500 mg orally twice daily for 7 days.
- Treatment (men): metronidazole 2 g orally as a single dose. A single 2 g dose of tinidazole is an alternative in both sexes.
- Partner management: the patient should notify partners for testing and treatment; avoid sex until both have completed treatment and symptoms have resolved.
- Retest within 12 weeks of treatment because of high rates of persistent infection and reinfection (CDC advice).
- Pregnancy and HIV: untreated infection is linked to preterm delivery, low birth weight and premature rupture of membranes; it is strongly associated with other STIs including HIV.
Which traps and one-liners come up in NEET PG and INI-CET?
- Clue cells + pH > 4.5 + fishy smell → BV; drug of choice metronidazole; no routine partner treatment.
- Normal pH + curdy discharge + itching → candidiasis; KOH shows pseudohyphae; fluconazole or topical azole.
- Frothy yellow-green discharge + strawberry cervix + motile flagellates → trichomoniasis; metronidazole; treat the partner.
- Gram stain with a Nugent score 7–10 = BV; Amsel needs 3 of 4.
- Oral fluconazole is avoided in pregnancy in CDC guidance — use topical azoles for 7 days.
- BV is not a simple STI, but a dysbiosis linked with sexual behaviour; it is associated with increased risk of acquiring STIs and with preterm birth and PROM.
- Persistent discharge with cervicitis, or pelvic pain, should prompt screening for gonorrhoea and chlamydia rather than assuming a simple vaginitis; also remember cervical cancer screening is separate from treating discharge.