Sexually Transmitted Infections
A group of infections transmitted by sexual contact, including chlamydia, gonorrhoea, syphilis, HIV, trichomoniasis, and viral hepatitis. UK care emphasises confidential testing, partner notification, and syndrome-based management when empirical therapy is required.
Key Facts
Key points
- Asymptomatic infection is common — screen high-risk groups and contacts.
- Dual testing for HIV and syphilis serology is routine in sexual health screens.
- Gonorrhoea: treat with ceftriaxone 1 g IM/IV plus azithromycin 1 g PO** (UK BASHH — check current national guidance for resistance patterns).
- Chlamydia: doxycycline 100 mg BD for 7 days first-line; azithromycin 1 g** alternative if pregnancy/doxycycline contraindicated (local policy).
- Partner notification: index case should inform partners from the relevant look-back period; clinics can use accelerated partner therapy where appropriate.
- PrEP (HIV pre-exposure prophylaxis) with tenofovir disoproxil/emtricitabine for eligible individuals — specialist initiation.
Overview
Epidemiology (UK context)
Highest rates are seen in young adults and MSM; inequality and stigma remain barriers to testing.
Syndromes
Urethritis, cervicitis, PID, epididymo-orchitis, proctitis, pharyngeal infection, genital ulceration.
Public health
Confidential GUM/sexual health services provide testing, treatment, and contact tracing.
Clinical Presentation
Presenting complaints
Urethral/vaginal discharge, dysuria, intermenstrual/post-coital bleeding, pelvic pain, testicular pain, anorectal symptoms, ulcers, rash.
Examination
Speculum examination where indicated; testicular examination; lymph nodes; rash (palmar/plantar in secondary syphilis).
Differential Diagnosis
| Syndrome | Important differentials |
|---|---|
| Urethritis | Gonorrhoea, chlamydia, Mycoplasma genitalium, UTI |
| Genital ulcer | Syphilis, HSV, chancroid (rare UK), lymphogranuloma venereum |
| Pelvic pain | PID, ectopic pregnancy, appendicitis, endometriosis |
Diagnosis / Investigation
Tests
- NAAT swabs/urine for chlamydia/gonorrhoea; extragenital sites as indicated.
- Syphilis serology (EIA + confirmatory algorithm).
- HIV Ag/Ab test with consent and pre-test discussion.
- Hepatitis B/C serology depending on risk.
- Microscopy of urethral discharge if available (Gram-negative diplococci).
Management
Empirical syndromic therapy (example — follow BASHH)
- Suspected gonorrhoea: ceftriaxone 1 g IM/IV stat + azithromycin 1 g PO stat.
- Chlamydia: doxycycline 100 mg BD 7 days.
Pelvic inflammatory disease (inpatient severe)
- Ceftriaxone 1 g IV OD + metronidazole 400 mg BD + doxycycline 100 mg BD (14-day course common) — per guideline.
Support
- Condoms, vaccination (HPV, hepatitis A/B where indicated), PrEP referral.
Prognosis
Most bacterial STIs are curable; viral infections (HSV, HIV, hepatitis) require longer-term management. Early treatment reduces complications (infertility, chronic hepatitis).
Other Relevant Information
Confidentiality and safeguarding
Follow GMC and local policies; involve safeguarding leads where minors or vulnerable adults are at risk.