Pathophysiology
PID Anatomical Spread
Infection ascends from cervix to upper genital tract structures
- General term for infection of upper genital tract
- Infection ascends from endocervix causing:
- Endometritis
- Salpingitis
- Parametritis
- Oophoritis
- Tubo-ovarian abscess
- Pelvic peritonitis
- Can involve multiple anatomical sites simultaneously
Causes & Microbiology
Primary Pathogens
- Chlamydia trachomatis (14–35% of cases)
- Neisseria gonorrhoeae (2–3% of cases)
- Mycoplasma genitalium (common cause)
Normal Vaginal Flora
- Anaerobes
- Gardnerella vaginalis
- Haemophilus influenzae
- Enteric Gram-negative rods
- Streptococcus agalactiae
Microbiological Causes of PID
Relative prevalence of different pathogens in PID cases
Risk Factors
Sexual Behavior
- Young age (<25 years)
- Early age of first coitus
- Multiple sexual partners
- Recent new partner (within 3 months)
- History of STI in woman or partner
Medical Procedures
- Termination of pregnancy
- Insertion of intrauterine device
- Hysterosalpingography
- In vitro fertilisation
- Intrauterine insemination
Clinical Features
Symptoms
- Pelvic/lower abdominal pain (usually bilateral)
- Deep dyspareunia (recent onset)
- Abnormal vaginal bleeding
- Abnormal vaginal/cervical discharge
- Right upper quadrant pain (Fitz-Hugh-Curtis)
- Secondary dysmenorrhoea
Signs
- Lower abdominal tenderness (bilateral)
- Adnexal tenderness ± mass
- Cervical motion tenderness
- Uterine tenderness
- Mucopurulent discharge
- Fever >38°C (often normal)
Clinical Presentation Patterns
Common symptom patterns and examination findings in PID
Investigations
Diagnostic Approach
Diagnose PID on clinical grounds. Do not delay treatment waiting for test results. Negative swabs do not rule out PID.
Essential Tests
Immediate Tests
- Pregnancy test (exclude ectopic)
- High vaginal swab (BV/candidiasis)
- Chlamydia NAAT
- Gonorrhoea NAAT
- Mycoplasma genitalium test
Microscopy & Blood Tests
- Endocervical/vaginal pus cells
- ESR, CRP, leucocyte count
- HIV test
- Syphilis serology
Imaging
Ultrasound & Advanced Imaging
- Ultrasound: Limited value in uncomplicated PID, helpful for abscess/hydrosalpinx
- Doppler ultrasound: Detects increased blood flow but non-specific
- MRI/CT: Helpful for differential diagnosis, not routine
Differential Diagnosis
Gynecological
- Ectopic pregnancy
- Threatened abortion
- Ruptured corpus luteal cyst
- Endometriosis
- Ovarian cyst complications
Gastrointestinal
- Acute appendicitis
- Irritable bowel syndrome
- Acute bowel infection
- Diverticular disease
Other
- Urinary tract infection
- Mittelschmerz pain
- Functional pain
Management
Empirical Antibiotic Therapy
- Start immediately on clinical diagnosis
- Broad spectrum coverage required
- Outpatient therapy effective for mild-moderate PID
Antibiotic Regimens
| Setting | Regimen | Duration |
|---|---|---|
| Outpatient |
Ceftriaxone 500mg IM single dose + Doxycycline 100mg BD + Metronidazole 400mg BD |
14 days |
| Inpatient |
IV Ceftriaxone + IV Doxycycline + IV Metronidazole |
Until 24h after improvement, then switch to oral |
Pain Management
- Ibuprofen or paracetamol for pain relief
- Assess response to analgesia
- Consider stronger analgesia if severe pain
Admission Criteria
Mandatory Admission
- Surgical emergency suspected
- No response to oral therapy
- Clinically severe disease
- Tubo-ovarian abscess
- Pregnancy
- Intolerance to oral therapy
Severe Disease Indicators
- Pyrexia >38°C
- Signs of pelvic peritonitis
- Systemically unwell
- Vomiting
- Significant abdominal guarding
Partner Management & Prevention
Partner Notification
- Current partners must be treated
- Recent partners (within 6 months)
- Offer screening, treatment, contact tracing
- Avoid unprotected sex until treatment complete
Surgical Management
Laparoscopy
- Divides adhesions
- Drains pelvic abscesses
- May aid early resolution
- Diagnostic and therapeutic
Ultrasound Guidance
- Less invasive than laparoscopy
- Aspiration of fluid collections
- Equally effective for drainage
- Preferred initial approach
Complications
Tubal Infertility
- Most serious long-term complication
- Risk increases with recurrent episodes
- Due to tubal damage and scarring
- Early treatment reduces risk
Ectopic Pregnancy
- 6-10x increased risk
- Due to impaired tubal function
- Lifelong increased risk
- Requires high index of suspicion
Chronic Pelvic Pain
- Occurs in 15-20% of cases
- Due to adhesions and scarring
- May be cyclical or constant
- Significant impact on quality of life
Tubo-ovarian Abscess
- Collection of pus in adnexa
- Requires drainage + antibiotics
- May rupture causing peritonitis
- Surgical emergency if ruptured
Fitz-Hugh-Curtis Syndrome
- Perihepatitis causing RUQ pain
- Especially with Chlamydia trachomatis
- "Violin string" adhesions on laparoscopy
- Responds to standard PID treatment
Long-term Complications of PID
Progression from acute infection to long-term complications