Key Facts

PID is an ascending infection of the upper female genital tract involving the uterus, fallopian tubes, and/or ovaries. Early diagnosis and treatment are crucial to prevent long-term sequelae including tubal infertility and ectopic pregnancy.

Epidemiology

• Affects approximately 1-2% of sexually active women per year
• Most common in women aged 15-24 years
• True incidence likely higher due to subclinical infection
• Chlamydia prevalence in UK: approximately 3-5% in under 25s

Aetiology

• Chlamydia trachomatis: 25-50% of cases (often subclinical)
• Neisseria gonorrhoeae: 5-10% (more acute presentation)
• Mycoplasma genitalium: increasingly recognised cause
• Anaerobes and other vaginal flora: Bacteroides, Gardnerella, Haemophilus
• Risk factors: age <25, multiple sexual partners, new sexual partner, no barrier contraception, previous PID/STI, IUD insertion (first 3 weeks)

Pathophysiology

• Ascending infection from the lower genital tract through the cervix
• Endometritis → salpingitis → tubo-ovarian abscess → peritonitis
• Inflammatory response causes tubal oedema, adhesion formation, and tubal damage
• Chronic inflammation leads to tubal occlusion and peritubal adhesions
• Fitz-Hugh-Curtis: infection spreads to hepatic capsule via peritoneal cavity

Typical Presentation

• Bilateral lower abdominal/pelvic pain (most common symptom)
• Abnormal vaginal discharge (purulent)
• Intermenstrual or postcoital bleeding
• Deep dyspareunia
• Fever and malaise (in moderate-severe cases)

Examination Findings

• Lower abdominal tenderness with guarding
• Cervical excitation (chandelier sign): pain on moving the cervix bimanually
• Adnexal tenderness (bilateral)
• Purulent cervical discharge on speculum

Red Flags

• Fever >38°C with peritonism (severe PID or tubo-ovarian abscess)
• Fitz-Hugh-Curtis syndrome (RUQ pain with PID symptoms)
• Pregnancy with PID symptoms (exclude ectopic)
• Palpable adnexal mass (tubo-ovarian abscess)
• Failed outpatient treatment

Bedside

• Pregnancy test (essential to exclude ectopic)
• Temperature measurement
• Speculum examination with endocervical swabs
• Bimanual examination: cervical excitation, adnexal tenderness

Bloods

• Endocervical swab: NAAT for Chlamydia and Gonorrhoea
• Mycoplasma genitalium NAAT (if available)
• HVS: for bacterial vaginosis and other organisms
• FBC, CRP, ESR (inflammatory markers elevated)
• Blood cultures if pyrexial

Imaging

• Pelvic USS (TVS): if tubo-ovarian abscess suspected (complex adnexal mass with fluid)
• MRI: if diagnosis uncertain

Special Tests

• Endometrial biopsy: histological evidence of endometritis (plasma cells) provides supportive evidence
• Laparoscopy: gold standard for diagnosis but rarely performed acutely; indicated if diagnosis uncertain or failed treatment

Non-pharmacological

• Rest, adequate hydration, analgesia
• Contact tracing and partner notification (essential)
• Advise abstinence from sexual intercourse until patient and partners have completed treatment
• Removal of IUD only if no clinical improvement after 48-72 hours of antibiotics (leaving IUD in does not worsen outcomes if antibiotics started)

Pharmacological

• Outpatient (mild-moderate PID) per BASHH guidelines:
  • IM ceftriaxone 1g STAT + doxycycline 100mg BD for 14 days + metronidazole 400mg BD for 14 days
  • Alternative: ofloxacin 400mg BD + metronidazole 400mg BD for 14 days (if gonococcal PID excluded)
• Inpatient (severe PID): IV ceftriaxone 2g OD + IV doxycycline 100mg BD + IV metronidazole 500mg TDS; step down to oral when improving
• If Mycoplasma genitalium positive: moxifloxacin 400mg OD for 14 days (after macrolide resistance testing)
• Test of cure: repeat NAAT for gonorrhoea at 2 weeks, Chlamydia at 6 weeks

Surgical/Interventional

• Tubo-ovarian abscess: USS-guided aspiration or laparoscopic/open drainage if not responding to antibiotics (48-72 hours)
• Laparoscopy: diagnostic and therapeutic (adhesiolysis, drainage)

Referral Criteria

• Admit if: severe PID (high fever, peritonism), tubo-ovarian abscess, failed outpatient treatment, unable to tolerate oral therapy, pregnancy, uncertain diagnosis
• GUM/sexual health clinic referral for partner notification and STI screening
• Gynaecology referral for persistent symptoms or suspected tubo-ovarian abscess

• With prompt treatment: most women recover fully with no long-term sequelae
• Tubal factor infertility: 10-20% after 1 episode, 20-30% after 2, 40-60% after ≥3 episodes
• Ectopic pregnancy risk: increased 6-10× after PID
• Chronic pelvic pain: develops in 18-30% of women after PID
• Fitz-Hugh-Curtis perihepatic adhesions may cause recurrent RUQ pain
• Reinfection is common if partners are not treated simultaneously

BASHH PID Treatment Summary

Long-term Sequelae by Number of PID Episodes