What causes Pelvic Inflammatory Disease (PID) and how is it treated?

Causes and Treatment of Pelvic Inflammatory Disease (PID)

Pelvic inflammatory disease (PID) is primarily caused by sexually transmitted infections, most commonly Chlamydia trachomatis and Neisseria gonorrhoeae, along with a variety of anaerobic and aerobic bacteria that ascend from the lower genital tract to the upper genital tract. 1

Etiology of PID

• PID results from direct canalicular spread of organisms from the endocervix to the endometrial and fallopian tube mucosa, with most cases being polymicrobial (involving multiple organisms) 1

• The primary causative organisms include:

  • Chlamydia trachomatis (found in 5-39% of cervical samples from women with PID) 1
  • Neisseria gonorrhoeae (found in 27-80% of cervical samples from women with PID) 1
  • Anaerobic bacteria (Bacteroides, Peptostreptococcus, and Peptococcus species) 1
  • Aerobic/facultative bacteria (Gardnerella vaginalis, Streptococcus species, Escherichia coli, and Haemophilus influenzae) 1
  • Mycoplasmas (including Mycoplasma genitalium), though their role is less clearly defined 1

• Bacterial vaginosis (BV) is often an antecedent to PID, with BV-associated organisms contributing to polymicrobial PID 1

Factors Contributing to PID Development

• Uterine instrumentation (e.g., insertion of an intrauterine device) facilitates upward spread of bacteria 1

• Hormonal changes during menstruation can lead to cervical alterations that remove mechanical barriers preventing ascent of organisms 1

• Retrograde menstruation may favor ascent of organisms to the fallopian tubes and peritoneum 1

• Individual organism virulence factors may contribute to the pathogenesis of PID 1

• Between 10-40% of women with untreated gonococcal or chlamydial cervicitis develop clinical symptoms of acute PID 1

Diagnosis of PID

Empiric treatment should be initiated in sexually active young women at risk for STDs if the following minimum criteria are present and no other cause for illness can be identified:

• Uterine/adnexal tenderness or cervical motion tenderness 1

Additional criteria supporting PID diagnosis include:

• Oral temperature >101°F (>38.3°C) 1
• Abnormal cervical or vaginal mucopurulent discharge 1
• Presence of white blood cells on saline microscopy of vaginal secretions 1
• Elevated erythrocyte sedimentation rate or C-reactive protein 1
• Laboratory documentation of cervical infection with N. gonorrhoeae or C. trachomatis 1

Treatment of PID

Treatment regimens must provide empiric, broad-spectrum coverage of likely pathogens including N. gonorrhoeae, C. trachomatis, anaerobes, gram-negative facultative bacteria, and streptococci to prevent long-term sequelae such as infertility, ectopic pregnancy, and chronic pelvic pain. 1, 2

Inpatient Treatment (Recommended for severe cases)

Recommended Regimen A:

• Cefoxitin 2g IV every 6 hours or cefotetan IV 2g every 12 hours 1, 3, 4
• Plus doxycycline 100mg orally or IV every 12 hours 1
• Continue for at least 48 hours after clinical improvement 1
• After discharge, continue doxycycline 100mg orally twice daily for a total of 10-14 days 1

Recommended Regimen B:

• Clindamycin IV 900mg every 8 hours 1
• Plus gentamicin loading dose IV or IM (2mg/kg) followed by maintenance dose (1.5mg/kg) every 8 hours 1
• Continue for at least 48 hours after improvement 1
• After discharge, continue doxycycline 100mg orally twice daily for 10-14 days 1

Criteria for Hospitalization

Hospitalization is particularly recommended when:

• The diagnosis is uncertain 1
• Surgical emergencies such as appendicitis or ectopic pregnancy cannot be excluded 1
• A pelvic abscess is suspected 1
• The patient is pregnant 1
• The patient is an adolescent (compliance may be unpredictable) 1
• Severe illness precludes outpatient management 1
• The patient is unable to tolerate an outpatient regimen 1
• The patient has failed to respond to outpatient therapy 1
• Clinical follow-up within 72 hours cannot be arranged 1

Outpatient Treatment (For mild to moderate cases)

• A single intramuscular injection of a recommended cephalosporin followed by oral doxycycline for 14 days 5
• Additionally, metronidazole is recommended for 14 days in cases of bacterial vaginosis, trichomoniasis, or recent uterine instrumentation 5

Prevention of PID

• Prevention of lower genital tract infections with C. trachomatis and N. gonorrhoeae 1
• Early detection and prompt treatment of lower tract infections 1
• Screening for C. trachomatis and N. gonorrhoeae in all women younger than 25 years and those at risk 5
• Intensive behavioral counseling for adolescents and adults at increased risk of STIs 5
• Treatment of sex partners; expedited partner treatment where legal 5

Important Clinical Considerations

• PID can be acute, chronic, or subclinical and is often underdiagnosed 5
• Untreated PID can lead to serious sequelae including chronic pelvic pain, infertility (12% after one episode, 25% after two episodes, and over 50% after three or more episodes), ectopic pregnancy, and intra-abdominal infections 1, 5
• Patients with tubo-ovarian abscess that does not respond to antibiotics should undergo surgical drainage 1
• Prevention of long-term sequelae has been linked directly with immediate administration of appropriate antibiotics 1