Differential Diagnosis for Green Vaginal Discharge in a Pessary User
The primary differential diagnosis for green vaginal discharge in a woman using a pessary is trichomoniasis, followed by bacterial vaginosis (BV), pessary-related inflammatory vaginitis, and less commonly vulvovaginal candidiasis with secondary bacterial infection.
Key Infectious Etiologies
Trichomoniasis (Most Likely for Green Discharge)
Trichomoniasis characteristically causes a diffuse, malodorous, yellow-green discharge with vulvar irritation 1, 2. This is the classic presentation for green-colored vaginal discharge and should be your first consideration regardless of pessary use. The diagnosis requires:
- Wet mount microscopy showing motile trichomonads (60-70% sensitivity)
- Culture (most sensitive commercially available method)
- pH typically >4.5
Bacterial Vaginosis
BV presents with a homogeneous, white-to-gray discharge rather than green 1, but can appear greenish when mixed with inflammatory exudate. In pessary users, BV prevalence may be higher (31.1% vs 22.2% in non-users) 3. Diagnosis requires 3 of 4 Amsel criteria:
- Homogeneous discharge adhering to vaginal walls
- Clue cells on microscopy
- pH >4.5
- Positive whiff test (fishy odor with KOH)
Pessary-Specific Considerations
Pessary-Related Inflammatory Vaginitis
Pessary users develop vaginal inflammation early (within 2 weeks) that persists with continued use 4. This inflammatory process causes:
- Increased vaginal discharge (84% of pessary users vs 62.2% non-users) 3
- More alkaline vaginal pH in women with erosions 5
- Altered vaginal microbiota with decreased lactobacilli and increased gram-negative bacteria 5
The discharge from pessary-related inflammation is typically not green but rather increased in volume and may appear discolored due to:
- Vaginal erosions (present in 20% of users) 3
- Bleeding from mucosal trauma
- Mixed bacterial overgrowth
Critical Pitfall: Erosions and Infection
Women with pessary erosions have significantly more complex vaginal microbiota with increased Bacteroidetes and Actinobacteria 5. However, the presence of erosions does NOT necessarily indicate infection—it represents mechanical trauma with secondary inflammatory changes.
Diagnostic Algorithm
Step 1: Obtain vaginal pH
- pH ≤4.5: Consider candidiasis (though typically white discharge)
- pH >4.5: Trichomoniasis or BV most likely
Step 2: Wet mount microscopy (saline and 10% KOH)
- Motile trichomonads = Trichomoniasis
- Clue cells + whiff test = BV
- Pseudohyphae = Candidiasis (uncommon with green discharge)
Step 3: Examine for pessary complications
- Vaginal erosions present
- Degree of inflammation
- Proper pessary fit and position
Step 4: Culture if microscopy negative
- Trichomonas culture (most sensitive)
- Consider aerobic/anaerobic cultures if severe inflammation
Treatment Priorities
For Trichomoniasis (if confirmed):
Metronidazole 2g orally single dose 2 with partner treatment mandatory. Alternative: metronidazole 500mg twice daily for 7 days.
For BV (if confirmed):
Metronidazole 500mg orally twice daily for 7 days 1. Alternative regimens include metronidazole gel 0.75% or clindamycin preparations.
For Pessary-Related Inflammation Without Infection:
- Continue pessary use if tolerated (83.7% develop adverse events but satisfaction remains high) 6
- Consider topical estrogen if postmenopausal (though 23.9% of practitioners fail to prescribe this) 7
- Schedule follow-up every 3-4 months for pessary care 6
Important Caveats
Do not assume green discharge is solely pessary-related. While pessaries cause increased discharge in 48.6% of users 7, the green color specifically suggests trichomoniasis until proven otherwise. Pessary-related discharge is typically clear to white, not green.
Vaginal erosions alone do not require pessary discontinuation. Only 16.3% of long-term users discontinue pessaries, and single erosions are not associated with discontinuation—only recurrent erosions 6.
Multiple infections can coexist. VVC can occur concomitantly with STDs, and pessary use does not protect against sexually transmitted infections 2.