Trichomoniasis is caused by a flagellated protozoan, Trichomonas vaginalis. It is always sexually transmitted.

Bacterial vaginosis is the most common cause of vaginitis, vaginal discharge or malodor. It results from overgrowth of anaerobic bacteria.

Vulvovaginal candidiasis is caused by overgrowth of yeasts where 70-90% of cases are secondary to Candida albicans. It most commonly occurs when the vagina is exposed to estrogen (ie, reproductive years, pregnancy) and may be precipitated by antibiotic use.


  • Clinical and sexual history, and physical examination are important parts of investigation


  • Inquire about characteristics of discharge (ie odor, onset eg association with menstrual cycle, duration, color, consistency) and any associated symptoms (eg itch, dysuria, dyspareunia, abdominal pain, abnormal vaginal bleeding)
  • Assess possible risk for sexually transmitted infections (ie <25 years old, new or multiple sexual partners, prior sexually transmitted infection)
  • Know other comorbid conditions (eg diabetes mellitus, immunocompromised states), contraception use, and history or current medication use

Physical Examination

  • Perform general assessment and look for signs of sexually transmitted infection
  • Examine mucocutaneous regions including the pharynx
  • External genitalia should be inspected for anatomical irregularities, cutaneous lesions, inflammation and urethral discharge
  • Perianal inspection
    • Digital rectal exam and anoscopy should be considered if patient has practiced receptive anal intercourse or has rectal symptoms
  • Inguinal lymph nodes should be palpated

Illuminated Speculum Exam

  • Visualize cervix and vaginal walls
  • Evaluate vagina and endocervical vaginal discharges (consistency, amount, color, odor, pH)
  • Observe for cervical mucopus, erosions, friability, foreign bodies, growth
  • If resources are available, obtain specimens
    • Cervical swab for Chlamydia test, gonorrhea culture
    • Vaginal swab for Gram stain and Trichomonas slide

Bimanual Pelvic Exam

  • Perform if upper genital tract infection is suspected
  • Detect uterine or adnexal masses, tenderness or cervical motion tenderness
    •  A finding of lower abdominal tenderness or cervical motion tenderness should prompt the attending physician to evaluate the patient for salpingitis and/or endometritis which are part of pelvic inflammatory disease (PID)
      • Treat patient accordingly (See Pelvic Inflammatory Disease Management Chart for details)
      • Differential diagnoses may also include other surgical or gynecological conditions

Laboratory Tests

Settings Where Diagnostic Lab Tests are Not Available

  • Consider syndromic management for patients presenting with vaginal discharge
  • A spontaneous complaint of abnormal vaginal discharge is most commonly a result of a vaginal infection T vaginalis, C albicans, and bacterial vaginosis are the commonest causes of altered vaginal discharge
  • In settings where Gram stain can be carried out in an efficient manner, identification of T vaginalis can be attempted
  • In settings where diagnostic tests for the etiologic agent of vaginal infection cannot be done, it is recommended that patients be offered treatment for bacterial vaginosis and T vaginalis

Specimen Collection in Settings Where Diagnostic Lab Tests are Available 

Collect vaginal specimens for the following:

  • pH test
    • Specimen should be obtained from the mid-portion of the vaginal side wall to avoid false elevations in pH secondary to cervical mucus, blood, or semen
  • Amine odor/whiff test
    • Considered positive if release of fishy odor occurs when swab from vaginal discharge is placed in 10% KOH
  • Wet mount with saline or 10% KOH
  • Gram stain
    • Dry Gram stain is the definitive diagnostic test for bacterial vaginosis
  • High vaginal swabs
    • Helps in diagnosing bacterial vaginosis, vulvovaginal candidiasis, T vaginalis, or other genital tract infections particularly in pregnant, postpartum, or post-instrumentation patients with recurrent or inconsistent signs and symptoms, or in treatment failure
  • Culture
    • Used to identify Candida when microscopy is inconclusive or in recurrent infection where identification of specific causative agent is useful

Lab Tests for Trichomoniasis:

  • pH: >4.5
  • Amine odor/whiff test: Not consistently positive
  • Wet mount with saline: Specimen from the posterior vaginal fornix may reveal motile flagellated trichomonads with polymorphonuclear cells
    • with low sensitivity
    • Should be performed as soon as possible after taking the sample as motility is decreased with time
  • Gram stain: May reveal T vaginalis and/or polymorphonuclear cells
  • Culture: Has higher sensitivity than microscopy
    • Considered in patients with negative wet mount test result, history of trichomoniasis with persistent symptoms even after treatment, or positive T vaginalis on Pap test
  • Nucleic acid amplification test: Has the highest sensitivity for T vaginalis detection
    • Should be the test of choice where diagnostic lab tests are available
  • Rapid tests for trichomoniasis include immunochromatographic capillary flow dipstick technology-based tests and nucleic acid probe test
    • Availability may be limited
  • Cervical screening (Pap smear) alone is not diagnostic of trichomoniasis

Lab Tests for Bacterial Vaginosis:

  • Culture is not recommended because of low specificity
  • Should fulfill 3 out of 4 of the Amsel’s criteria:
    • Abnormal thin gray/white vaginal discharge
    • pH: >4.5
    • Amine odor/whiff test: Positive
    • Wet mount with saline: Presence of clue cells (epithelial cells with granular appearance and obscured borders caused by adherent bacteria)
  • Gram Stain: May reveal a shift in vaginal flora with a decrease in large Gram-positive rods and a marked increase in smaller Gram-variable coccobacilli (Nugent’s criteria)
    • Considered to be the gold standard in diagnosing patients who fail to fulfill the Amsel’s criteria

Lab Tests for Vulvovaginal Candidiasis:

  • pH: 4-4.5
  • Amine odor/whiff test: Negative
  • Wet Mount with 10% KOH: Typically shows budding yeast and/or branching pseudohyphae
  • Gram Stain: May reveal polymorphonuclear cells, budding yeast and/or branching pseudohyphae
  • Culture: Positive for yeast species
    • Not routinely indicated; should be obtained in patients with recurrent vulvovaginal candidiasis, possible non-albicans candidiasis, or symptomatic patients with negative microscopy
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