Bacterial vaginosis vs Trichomonas and Candida vaginitis
How to tell Bacterial vaginosis and Trichomonas and Candida vaginitis apart when a board question makes them look alike.
BV is fishy clue cells; Trichomonas is frothy motile strawberry cervix; Candida is itchy thick white pseudohyphae with normal pH.
Side by side
Bacterial vaginosis causes thin gray fishy discharge, elevated vaginal pH, positive whiff test, and clue cells without prominent inflammation.
Trichomonas causes frothy green-yellow discharge, strawberry cervix, motile organisms, and high pH; Candida causes thick white discharge, itching, pseudohyphae, and normal pH.
BV reflects loss of lactobacilli and overgrowth of anaerobes such as Gardnerella, producing amines and biofilm.
Trichomonas is a sexually transmitted flagellated protozoan; Candida is yeast overgrowth, often after antibiotics, diabetes, or immunosuppression.
Clue cells, fishy odor with KOH, and pH above 4.5 support BV.
Motile trichomonads and strawberry cervix support trichomoniasis; budding yeast/pseudohyphae on KOH support Candida.
The trap
Vaginal discharge alone does not pick the diagnosis. The deciding triad is pH, microscopy, and amine (whiff) test: (1) bacterial vaginosis is a polymicrobial overgrowth (Gardnerella vaginalis with anaerobes) with pH ABOVE 4.5, gray thin discharge, positive whiff test on KOH, and clue cells (epithelial cells coated with bacteria) on saline wet mount; treat with metronidazole; (2) trichomoniasis is a sexually transmitted protozoan (Trichomonas vaginalis) with pH ABOVE 4.5, frothy yellow-green discharge, motile flagellated trichomonads on wet mount, strawberry cervix on exam; treat both partners with metronidazole; (3) candidiasis is yeast overgrowth (often after antibiotics, in diabetes or pregnancy) with NORMAL pH UNDER 4.5, thick white cottage-cheese discharge, itching, pseudohyphae on KOH; treat with topical or oral azole.
The repair move
For vaginitis, use pH and microscopy before relying on discharge description alone.
Try a free question
CoreA 28-year-old sexually active woman has 1 week of thin gray-white vaginal discharge with a fishy odor most noticeable after intercourse. Pelvic exam shows minimal vulvar irritation. Vaginal pH is 5.2, KOH whiff test is positive, and saline wet mount shows epithelial cells coated with bacteria obscuring cell borders. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Bacterial vaginosis. Bacterial vaginosis is diagnosed by Amsel criteria: thin homogeneous discharge, pH >4.5, positive whiff test, and clue cells on wet mount; it is dysbiosis with Gardnerella overgrowth rather than infection.
Why the other choices are tempting
- B. Trichomoniasis causes frothy yellow-green discharge with strawberry cervix and motile organisms, not clue cells.
- C. Candida produces thick white cottage-cheese discharge with intense pruritus, normal pH (<4.5), and budding yeast/pseudohyphae on KOH.
- D. Atrophic vaginitis occurs in low-estrogen states with thin friable mucosa, not clue cells.
- E. Chlamydia cervicitis causes mucopurulent cervical discharge and friable cervix, not thin gray vaginal discharge.
Flashcards
Tap a card to flip it.
What microscopy finding supports BV?
Clue cells support bacterial vaginosis.
What pH pattern supports Candida?
Normal vaginal pH supports Candida compared with BV or Trichomonas.
Quick answers
What is the fastest way to tell Bacterial vaginosis from Trichomonas and Candida vaginitis?
BV is fishy clue cells; Trichomonas is frothy motile strawberry cervix; Candida is itchy thick white pseudohyphae with normal pH.
What is the key clue for Bacterial vaginosis?
Bacterial vaginosis causes thin gray fishy discharge, elevated vaginal pH, positive whiff test, and clue cells without prominent inflammation.
What is the key clue for Trichomonas and Candida vaginitis?
Trichomonas causes frothy green-yellow discharge, strawberry cervix, motile organisms, and high pH; Candida causes thick white discharge, itching, pseudohyphae, and normal pH.
What is the common trap with Bacterial vaginosis vs Trichomonas and Candida vaginitis?
Vaginal discharge alone does not pick the diagnosis. The deciding triad is pH, microscopy, and amine (whiff) test: (1) bacterial vaginosis is a polymicrobial overgrowth (Gardnerella vaginalis with anaerobes) with pH ABOVE 4.5, gray thin discharge, positive whiff test on KOH, and clue cells (epithelial cells coated with bacteria) on saline wet mount; treat with metronidazole; (2) trichomoniasis is a sexually transmitted protozoan (Trichomonas vaginalis) with pH ABOVE 4.5, frothy yellow-green discharge, motile flagellated trichomonads on wet mount, strawberry cervix on exam; treat both partners with metronidazole; (3) candidiasis is yeast overgrowth (often after antibiotics, in diabetes or pregnancy) with NORMAL pH UNDER 4.5, thick white cottage-cheese discharge, itching, pseudohyphae on KOH; treat with topical or oral azole.