Pelvic inflammatory disease

Overview

PID = infection and inflammation of the upper female genital tract (endometrium, fallopian tubes, ovaries, pelvic peritoneum). Predominantly affects sexually active women under 25. Prompt empirical treatment is the cornerstone - missed diagnosis risks infertility, ectopic pregnancy, and chronic pelvic pain.

Aetiology

Ascending polymicrobial infection - key pathogens:

•Chlamydia trachomatis - most common STI-related cause; indolent but destructive

•Neisseria gonorrhoeae - more acute, florid presentation; rates rising in UK

•Mycoplasma genitalium - increasingly important; requires specific cover; emerging resistance

•Anaerobes/endogenous flora (e.g. Gardnerella, Bacteroides) - contribute in BV-associated PID and tubo-ovarian abscess

📌

IUCD is associated with increased PID risk in the first 3 weeks after insertion only (procedure-related). After this window, IUCD in situ does not increase risk. If PID develops within 3 weeks of insertion, treat with antibiotics; removal is not routinely required unless the patient fails to improve.

Presentation

•Lower abdominal/pelvic pain - bilateral, dull, recent onset (cardinal symptom)

•Deep dyspareunia

•Abnormal vaginal discharge - mucopurulent

•Abnormal uterine bleeding - intermenstrual or post-coital

•Fever (>38°C) - suggests more severe infection; often absent in mild PID

•Right upper quadrant pain - Fitz-Hugh-Curtis syndrome (perihepatitis); up to 10% of cases

•Bimanual examination: uterine tenderness + adnexal tenderness + cervical motion tenderness (CMT) - minimum clinical criteria for working diagnosis

🎯

CMT (pain on moving the cervix side to side) is the most specific sign. A working diagnosis of PID can be made on clinical examination alone - do NOT wait for swab results before starting empirical antibiotics.

Investigations

🥇 First-line

•urine pregnancy test (βhCG) - must exclude ectopic pregnancy

•high vaginal swab + endocervical swab - NAAT for Chlamydia, Gonorrhoea, M. genitalium; microscopy for BV

•CRP and WCC - support diagnosis and gauge severity; normal values do NOT exclude PID

•HIV and syphilis serology - offered as part of STI screen

•pelvic ultrasound - if tubo-ovarian abscess suspected; may be normal in uncomplicated PID

🏆 Gold standard

•laparoscopy with direct visualisation of tubes - reserved for diagnostic uncertainty or failure to respond to treatment

Management

•Indications for urgent hospital admission:

•Pregnancy or suspected ectopic pregnancy

•Tubo-ovarian abscess

•Surgical emergency cannot be excluded (e.g. appendicitis)

•Severe systemic illness (high fever, peritonism, vomiting, unable to take oral medication)

•Failure to respond to oral antibiotics within 72 hours

•Adolescents (consider admission)

PID antibiotic regimens (BASHH 2019)

Setting	Regimen
Outpatient first-line	Ceftriaxone 1g IM single dose + doxycycline 100mg orally BD + metronidazole 400mg orally BD - all for 14 days (except ceftriaxone)
Outpatient alternative (M. genitalium suspected/confirmed or ceftriaxone unavailable)	Moxifloxacin 400mg orally OD for 14 days; OR ofloxacin 400mg orally BD + metronidazole 400mg orally BD for 14 days (fluoroquinolone cautions: not under 18, tendon risk)
Inpatient IV first-line	Ceftriaxone 2g IV OD + doxycycline 100mg orally/IV BD + metronidazole 500mg IV TDS - step down to oral when improving
Inpatient IV alternative	Clindamycin 900mg IV TDS + gentamicin (weight-based dosing)

•Analgesia - NSAIDs

•Abstain from intercourse until woman and all partners have completed treatment and are symptom-free

•Partner notification - all partners in past 6 months; screen and treat empirically; coordinate via sexual health clinic

Follow-up

•Review within 72 hours for all women managed in primary care - assess clinical response, review swab sensitivities, consider admission if not improving

•Continue antibiotics even if swabs return negative - negative swab does NOT exclude PID

•Test of cure (TOC): gonorrhoea - repeat at 2-4 weeks; chlamydia - repeat at 3-5 weeks if symptoms persist; M. genitalium - repeat at 4 weeks with resistance testing

Complications

•Tubo-ovarian abscess - IV antibiotics ± surgical/radiological drainage; up to 15% of hospitalised cases

•Tubal factor infertility - cumulative risk: ~10% after 1st episode, ~30% after 2nd, ~60% after 3rd

•Ectopic pregnancy - risk ~6-10x higher after PID (tubal scarring)

•Chronic pelvic pain - pelvic adhesions; ~20% of women after PID

•Fitz-Hugh-Curtis syndrome - perihepatitis; RUQ pain; 'violin string' adhesions on laparoscopy; occurs with both chlamydial and gonococcal PID

⚠️

Infertility risk is cumulative and dose-dependent. Prompt treatment and prevention of recurrence are critical for long-term reproductive outcomes.