What are the considerations for a young adult presenting with tender inguinal nodes after unprotected sex?

Tender Inguinal Nodes After Unprotected Sex: Clinical Approach

Tender inguinal lymphadenopathy following unprotected sexual contact in a young adult requires immediate empirical treatment for sexually transmitted infections (STIs), specifically gonorrhea, chlamydia, and trichomoniasis, while simultaneously testing for these infections plus syphilis and HIV. 1

Immediate Clinical Assessment

Key History Elements

• Timing of exposure: Document when unprotected sexual contact occurred (critical for HIV post-exposure prophylaxis window of 72 hours) 1
• Characteristics of lymphadenopathy: Assess for unilateral vs bilateral involvement, size, mobility, fixation to surrounding structures, and presence of overlying skin changes 1
• Associated symptoms: Evaluate for urethral/vaginal discharge, dysuria, genital lesions or ulcers, fever, and systemic symptoms 2, 3
• Sexual history: Number of partners, types of sexual contact (oral, vaginal, anal), partner symptoms, and geographic HIV prevalence 1

Physical Examination Priorities

• Inguinal examination: Document number of nodes, dimensions, tenderness, mobility, relationship to skin and Cooper's ligament, and presence of scrotal/penile/leg edema 1
• Genital examination: Inspect for urethral discharge, penile/vulvar lesions, ulcers, vesicles, or signs of trauma 1, 4
• Extragenital sites: Examine pharynx and perianal area if oral or anal contact occurred 1

Differential Diagnosis Framework

Most Likely STI Causes

The most common STIs causing inguinal lymphadenopathy include:

• Lymphogranuloma venereum (LGV): Causes tender, often unilateral inguinal/femoral lymphadenopathy that may progress to suppuration 3
• Primary syphilis: Painless chancre with firm, non-tender regional lymphadenopathy (though nodes can be tender) 2, 3
• Genital herpes (HSV): Painful vesicles/ulcers with tender bilateral inguinal adenopathy 2, 3
• Chancroid: Painful genital ulcer with tender, suppurative inguinal nodes 3

Common Non-Ulcerative STIs

• Gonorrhea and chlamydia: Typically cause urethritis/cervicitis without significant lymphadenopathy, but can occur with disseminated infection 1, 2
• Trichomoniasis: Usually presents with discharge rather than lymphadenopathy 1

Diagnostic Testing Strategy

Immediate Testing (Day 1)

• Nucleic acid amplification tests (NAATs): First-void urine for gonorrhea and chlamydia (sensitivity 86.1-100%, specificity 97.1-100%) 2
• Site-specific testing: If oral or anal penetration occurred, obtain pharyngeal and rectal NAATs 1
• Syphilis serology: Both treponemal and nontreponemal antibody tests 2
• HIV testing: Baseline test essential for post-exposure prophylaxis decision-making 1
• Herpes testing: If vesicles or ulcers present, obtain HSV NAAT from lesion 2

Critical pitfall: Up to 70% of chlamydia and trichomoniasis infections and 53-100% of extragenital gonorrhea/chlamydia are asymptomatic, so absence of discharge does not exclude infection 2

Empirical Treatment Protocol

Immediate Antimicrobial Therapy

Administer empirical treatment at the first visit without waiting for test results: 1

• Ceftriaxone 500 mg IM (single dose) for gonorrhea 1
• Doxycycline 100 mg PO twice daily for 7 days for chlamydia 1
  • Alternative: Azithromycin 1 g PO single dose (though doxycycline preferred for efficacy) 1, 5
• Metronidazole 2 g PO (single dose) for trichomoniasis 1
  • Alternative: Tinidazole 2 g PO single dose if alcohol ingestion or drug interactions are concerns 1

Rationale: The CDC explicitly recommends empirical treatment for all three infections following potential sexual exposure, as waiting for results delays treatment and risks ongoing transmission 1

HIV Post-Exposure Prophylaxis (PEP) Decision

Initiate HIV PEP within 72 hours if any high-risk factors present: 1

• Multiple perpetrators/partners
• Known HIV-positive partner
• High HIV prevalence geographic area
• Partner with genital lesions
• Presence of genital trauma or bleeding
• Receptive anal intercourse

Critical timing: PEP effectiveness decreases significantly after 72 hours; ideally start within 24 hours 1

Follow-Up Testing Schedule

Week 1-2

• Assess clinical response to antibiotics 1
• Review initial test results and adjust treatment if needed 1
• Pregnancy test at 2 weeks if female patient 1

Week 6

• Repeat syphilis serology if initial test negative and exposure risk high 1

Month 3

• Repeat HIV testing 1
• Repeat syphilis serology 1

Month 6

• Final HIV testing if initial negative 1

Vaccination Considerations

Immediate Immunization Opportunities

• Hepatitis B vaccine: Initiate series if not previously vaccinated 1
• HPV vaccine: Initiate or complete series (recommended starting age 9 years through age 26) 1

Common Clinical Pitfalls

Testing Errors

• Waiting for test results before treating: This delays care and increases transmission risk; empirical treatment is standard of care 1
• Using only urine NAATs when extragenital exposure occurred: Pharyngeal and rectal sites require separate specimen collection 1
• Relying on physical examination alone: 70% of infections are asymptomatic 2

Treatment Errors

• Omitting trichomoniasis coverage: This is explicitly included in CDC sexual assault prophylaxis guidelines 1
• Missing the 72-hour PEP window: HIV prophylaxis must be considered urgently 1
• Using inadequate gonorrhea treatment: Ceftriaxone 500 mg IM is now the recommended dose due to emerging resistance 1

Follow-Up Failures

• Not arranging mental health support: Sexual assault victims have increased rates of depression, suicidal ideation, and PTSD 1
• Inadequate partner notification: Contact tracing is essential for STI control 2
• Missing repeat HIV testing: Seroconversion can occur up to 6 months post-exposure 1

Special Considerations for Lymphadenopathy

When Nodes Suggest Specific Diagnoses

• Suppurative/fluctuant nodes: Consider LGV or chancroid; may require aspiration (never incision) 3
• Firm, non-tender nodes with painless ulcer: Classic for primary syphilis 2, 3
• Bilateral tender nodes with vesicles: Typical for primary HSV 2, 3

Red Flags Requiring Urgent Specialist Referral

• Nodes fixed to underlying structures or skin 1
• Progressive enlargement despite appropriate antibiotics 1
• Systemic symptoms (fever, weight loss, night sweats) suggesting disseminated infection or alternative diagnosis 1