Bacterial Vaginosis
A 26-year-old woman presents with 2 weeks of thin, greyish-white vaginal discharge with a fishy odour that is worse after intercourse. She has no itching, dysuria, or dyspareunia. Speculum examination shows discharge coating the vaginal walls with no vulval or vaginal erythema and no cervical motion tenderness. Vaginal pH is 5.0, and potassium hydroxide releases a pungent amine odour. Which of the following is the most likely diagnosis?
- A.Gonococcal cervicitis
- B.Trichomonas vaginalis infection
- C.Vulvovaginal candidiasis
- D.Bacterial vaginosisCorrect
Explanation
Bacterial vaginosis results from replacement of the normal hydrogen peroxide producing Lactobacillus flora by an overgrowth of anaerobes such as Gardnerella vaginalis, Prevotella, and Mobiluncus, which generate volatile amines. The diagnosis is clinical using the Amsel criteria, requiring three of four features: thin homogeneous discharge, vaginal pH above 4.5, a positive whiff test after adding potassium hydroxide, and clue cells on saline microscopy. This patient has the characteristic discharge, an elevated pH, and a positive amine test, which is sufficient. Importantly, bacterial vaginosis is not an inflammatory condition, which explains the absence of pruritus, dysuria, and vulvovaginal erythema. Trichomoniasis also raises vaginal pH and can produce a malodorous discharge, but it is typically frothy yellow-green with vulvovaginal irritation, dysuria, and a strawberry cervix, and motile trichomonads are seen on wet mount. Candidiasis causes intense pruritus with thick white curd-like discharge and a normal pH of 4.0 to 4.5. Gonococcal cervicitis produces mucopurulent cervical discharge with a friable cervix and often coexists with chlamydia. First-line treatment is oral or intravaginal metronidazole, or intravaginal clindamycin; routine treatment of male partners is not recommended. In pregnancy, bacterial vaginosis is associated with preterm labour and premature rupture of membranes, so symptomatic pregnant women should be treated.
Why each option
- A.
- Gonorrhoea causes mucopurulent cervicitis with a friable bleeding cervix and often dysuria or pelvic pain, none of which are present here.
- B.
- Trichomoniasis raises vaginal pH but characteristically causes a frothy yellow-green discharge with vulvar irritation, dysuria, and a punctate strawberry cervix.
- C.
- Candidiasis presents with intense pruritus and thick white curd-like discharge and characteristically has a normal vaginal pH of 4.0 to 4.5.
- D.
- Correct. Thin homogeneous discharge, pH above 4.5, and a positive whiff test satisfy the Amsel criteria for bacterial vaginosis in a non-inflamed vagina.
Reference: CDC Sexually Transmitted Infections Treatment Guidelines, 2021; Williams Gynecology, 4th ed., 2020
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