Management of Green Discharge and Post-Coital Dysuria with Negative STI Testing
Despite negative STI testing, this patient should be treated empirically for nongonococcal urethritis (NGU) with doxycycline 100 mg orally twice daily for 7 days, as the most common causes of NGU (Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma genitalium, and Trichomonas vaginalis) may not be detected by standard STI panels. 1
Clinical Context and Diagnostic Considerations
The presentation of green discharge with burning after intercourse is consistent with urethritis, even when initial STI tests are negative. 1, 2
Key diagnostic points:
- Urethritis is confirmed by mucopurulent/purulent discharge, ≥5 white blood cells per oil immersion field on urethral Gram stain, or ≥10 white blood cells per high-power field in first-void urine 1, 2
- C. trachomatis causes only 23-55% of NGU cases, with the proportion declining over time 1
- Ureaplasma urealyticum accounts for 20-40% of NGU cases, and Trichomonas vaginalis causes 2-5% 1
- The etiology of many NGU cases remains unknown even with comprehensive testing 1
Treatment Algorithm
First-Line Treatment
Doxycycline 100 mg orally twice daily for 7 days 1, 2, 3
This regimen provides coverage for:
- Chlamydia trachomatis (if missed by initial testing) 2, 4
- Ureaplasma urealyticum 1
- Mycoplasma genitalium (partial coverage) 2, 3
Alternative Regimens (if doxycycline contraindicated)
- Erythromycin base 500 mg orally 4 times daily for 7 days, OR 1
- Erythromycin ethylsuccinate 800 mg orally 4 times daily for 7 days 1
For patients intolerant of high-dose erythromycin:
- Erythromycin base 250 mg orally 4 times daily for 14 days, OR 1
- Erythromycin ethylsuccinate 400 mg orally 4 times daily for 14 days 1
Management of Persistent or Recurrent Symptoms
If symptoms persist or recur after completing initial therapy: 1
First, assess compliance and re-exposure:
- Re-treat with initial regimen if poor compliance or re-exposure to untreated partner 1
If compliance was adequate and no re-exposure:
- Perform wet mount examination and culture of intraurethral swab for Trichomonas vaginalis 1
- If T. vaginalis is positive, treat with metronidazole 2 g orally as single dose 1, 3
- If T. vaginalis is negative, re-treat with extended alternative regimen (erythromycin base 500 mg orally 4 times daily for 14 days) to cover possible tetracycline-resistant U. urealyticum 1
Partner Management
Sexual partners must be evaluated and treated: 1
- Partners with last sexual contact within 30 days of symptom onset should be evaluated and treated 1
- If the patient is asymptomatic, partners with contact within 60 days of diagnosis should be evaluated and treated 1, 5
- Patient should abstain from sexual intercourse until both patient and partners complete therapy and are symptom-free 1, 2
Important Caveats and Pitfalls
Common pitfalls to avoid:
- Do not rely solely on negative STI testing to exclude urethritis—many causative organisms are not detected by standard panels 1, 5
- Specific diagnostic tests for U. urealyticum are not routinely indicated and would not alter initial therapy 5
- Do not re-treat based on symptoms alone without documenting objective signs of urethral inflammation (discharge or elevated WBC count) 1
- Ensure partner treatment to prevent reinfection—this is a leading cause of treatment failure 1, 6
For persistent symptoms after doxycycline and erythromycin:
- Reassure the patient that persistent NGU does not cause known complications and is not necessarily sexually transmitted 1
- However, re-evaluate if exposed to new sexual partner 1
- Urologic examination rarely reveals specific etiology in these cases 1
Follow-Up Recommendations
- Return for evaluation only if symptoms persist or recur after completing therapy 1
- Failure to improve within 3 days of starting treatment requires re-evaluation of diagnosis and therapy 1
- Repeat testing for STIs should occur at 3 months after treatment 2
- Avoid repeat testing less than 3 weeks after treatment due to risk of false-positive results 2