What are the differential diagnoses for vaginal pruritus?

Differential Diagnoses for Vaginal Pruritus

Vaginal itching is most commonly caused by vulvovaginal candidiasis, but a systematic evaluation must also consider bacterial vaginosis, trichomoniasis, atrophic vaginitis (especially in postmenopausal women), and noninfectious causes including contact dermatitis and vulvar eczema. 1

Primary Infectious Causes

Vulvovaginal Candidiasis (VVC)

• VVC is the leading cause of vaginal itching, presenting as the most specific symptom and sometimes the only complaint 1
• Characterized by thick, white "cottage-cheese" discharge, severe vulvar pruritus, and vaginal pH ≤ 4.5 2, 1
• Diagnosis is confirmed by microscopy showing yeast or pseudohyphae on 10% KOH preparation, or by culture 1
• Important caveat: 10–20% of women are asymptomatic carriers of Candida species, so treatment should be based on both symptoms and laboratory findings, not colonization alone 2, 1

Bacterial Vaginosis (BV)

• Accounts for 40–50% of vaginitis cases when a cause is identified 3
• Presents with malodorous discharge (fishy odor) with minimal irritation rather than prominent itching 1
• Vaginal pH > 4.5, positive whiff test, and clue cells on saline wet mount are diagnostic 2, 1
• Key distinction: BV typically causes discharge and odor but is not a primary cause of intense itching 1

Trichomoniasis

• Accounts for 15–20% of vaginitis cases 3
• Presents with malodorous yellow-green frothy discharge, dysuria, and vulvar irritation 1
• Vaginal pH > 4.5 and motile trichomonads on wet mount (though sensitivity is only 60–70%) 2
• Nucleic acid amplification testing (NAAT) is preferred when clinical suspicion is high due to low wet-mount sensitivity 2, 1

Cervicitis (Gonorrhea/Chlamydia)

• Neisseria gonorrhoeae or Chlamydia trachomatis may uncommonly cause vaginal discharge but rarely present with itching as the primary symptom 4
• NAAT testing from vaginal swab has 97.1–100% sensitivity and specificity 2

Noninfectious Causes

Atrophic Vaginitis (Genitourinary Syndrome of Menopause)

• Critical diagnosis in postmenopausal women presenting with vaginal itching, dryness, irritation, and dyspareunia 5, 6
• Vaginal pH > 4.5 with absence of lactobacilli on microscopy 5
• Results from estrogen deficiency leading to thinning of vaginal epithelium 7, 8

Contact Dermatitis/Irritant Vaginitis

• Caused by mechanical, chemical, or allergic irritation from soaps, detergents, douches, or hygiene products 1
• Presents with external vulvar inflammation and minimal discharge 4, 1
• Objective signs of vulvar inflammation without vaginal pathogens suggest this diagnosis 4

Vulvar Eczema

• A chronic dermatosis causing vulvar pruritus requiring restoration of epidermal barrier function 1
• Diagnosis is clinical based on characteristic skin findings 1

Desquamative Inflammatory Vaginitis

• Associated with hypoestrogenism and encountered in persistent vaginitis cases 9
• May improve with topical clindamycin and steroid application 3

Diagnostic Algorithm

Step 1: Measure vaginal pH with narrow-range pH paper 2

• pH ≤ 4.5 → Consider VVC
• pH > 4.5 → Consider BV, trichomoniasis, or atrophic vaginitis

Step 2: Perform wet mount microscopy 2, 1

• Saline preparation: Look for clue cells (BV) or motile trichomonads (trichomoniasis)
• 10% KOH preparation: Look for yeast/pseudohyphae (VVC) and perform whiff test

Step 3: Apply Amsel criteria for BV (≥3 of 4 required) 2

• Homogeneous discharge
• Clue cells on microscopy
• pH > 4.5
• Positive whiff test (fishy odor with KOH)

Step 4: Consider NAAT testing 2, 1

• For Trichomonas vaginalis when wet mount is negative but suspicion is high
• For N. gonorrhoeae and C. trachomatis if mucopurulent cervical discharge is present

Step 5: Culture when indicated 1, 9

• Yeast culture with speciation for recurrent or complicated VVC
• Differentiates Candida albicans from non-albicans species (e.g., C. glabrata), which has important treatment implications

Common Pitfalls to Avoid

• Do not rely on symptoms alone to distinguish between causes—symptoms overlap significantly and mixed infections are common 1
• Do not treat asymptomatic Candida colonization—treatment should be based on both symptoms and laboratory findings 2, 1
• Do not use wet mount alone for trichomoniasis—NAAT is superior due to higher sensitivity 2, 1
• Do not confuse urine pH with vaginal pH—they are measured from different anatomic sites and are not correlated for vaginitis diagnosis 2
• In postmenopausal women, do not overlook atrophic vaginitis—it is a common and treatable cause of vaginal itching 5, 6
• Laboratory confirmation before treatment is essential, especially for first episodes, to avoid inappropriate therapy that may delay correct diagnosis 1, 6