Pelvic Inflammatory Disease (PID) — Comprehensive Notes

1. Definition

• Colpitis — vaginal infection
• Endocervicitis — cervical infection
• Endometritis — uterine infection
• Salpingitis — fallopian tube infection (most clinically significant component)
• Oophoritis — ovarian infection
• Tubo-ovarian abscess (TOA)
• Pelvic peritonitis

PID is a common and serious complication of sexually transmitted diseases (STDs). The standard clinical diagnosis is confirmed laparoscopically in only ~70% of cases — meaning diagnostic error is significant.

2. Pathogenesis & Spread

Vagina/Cervix → Endometrium (endometritis) → Fallopian tubes (salpingitis)
             → Ovaries (oophoritis) → Pelvic peritonitis → Tubo-ovarian abscess
             → Perihepatic/perisplenic adhesions (Fitz-Hugh-Curtis syndrome)

• Secondary extension from adjacent foci (appendicitis, diverticulitis, Crohn's)
• Hematogenous spread (e.g., tuberculosis, staphylococcal bacteremia)
• Iatrogenic — after D&C, IUD insertion, hysterosalpingography, termination of pregnancy

Symptoms frequently begin during or just after menstruation — this suggests menstrual flow facilitates cervicovaginal organisms ascending into the uterus.

3. Microbial Etiology

N. gonorrhoeae and C. trachomatis are co-present in ~25–75% of patients. Because exact microbial etiology is hard to determine without invasive sampling, treatment is always empirical and broad-spectrum.

4. Epidemiology & Risk Factors

Risk Factors

Why does adolescence confer risk? The cervical ectropion (larger transformation zone) present in younger women creates a larger surface area vulnerable to N. gonorrhoeae and C. trachomatis attachment.

Why does the IUD increase risk? Risk is highest within the first 3 weeks after insertion, likely due to disruption of the endocervical mucus barrier during the procedure. The risk returns to baseline after this window.

5. Clinical Manifestations & Symptoms

Endometritis (lower-tract disease)

• Less prominent tenderness; milder presentation
• Less often associated with fever or elevated CRP
• May be the only manifestation in subclinical PID

Salpingitis (upper-tract disease — classic PID)

• Bilateral, worse with movement, intercourse, or menstruation

• Abnormal vaginal discharge (purulent, increased)
• Dyspareunia (pain during/after sex)
• Intermenstrual or post-coital bleeding
• Fever (often with chills)
• Nausea, vomiting, dizziness
• Dysuria, urinary frequency
• Lower back pain, leg pain

Important caveat: symptoms alone are not a reliable predictor. Clinical diagnosis without additional criteria is inadequate.

6. Diagnosis

Clinical Diagnostic Criteria

The CDC minimum threshold: treatment should be initiated empirically in any sexually active woman with pelvic or lower abdominal pain if one of the three major criteria is present on pelvic examination, and no other cause is identified.

Major Criteria (all three must be present for clinical diagnosis)

1. Cervical motion tenderness (CMT) — "chandelier sign"
2. Uterine tenderness
3. Adnexal tenderness

Minor Criteria (increase specificity)

• Fever > 38.3°C
• Abnormal cervical/vaginal discharge
• Leukocytosis > 10 × 10⁹ WBC/L
• Elevated ESR
• Elevated CRP
• Pelvic abscess or inflammatory complex on bimanual examination
• Gram stain of endocervix showing gram-negative intracellular diplococci
• Positive chlamydia test

Definitive Diagnostic Criteria

1. Endometrial biopsy — histopathologic evidence of endometritis
2. Transvaginal ultrasound — thickened fluid-filled fallopian tubes ± free pelvic fluid or tubo-ovarian complex
3. Laparoscopy — gold standard; direct visualization of abnormalities consistent with PID

Investigations

7. Differential Diagnosis

8. Complications

9. Treatment

When to Hospitalize

• Surgical emergency (e.g., appendicitis) cannot be excluded
• Pregnancy
• Failure to respond to oral antibiotics after 72 hours
• Unable to tolerate oral regimen (nausea/vomiting)
• Severe illness, high fever
• Tubo-ovarian abscess
• HIV with low CD4 count

Parenteral (IV/IM) Regimens — Inpatient

• Cefoxitin 2 g IV every 6 hours + Doxycycline 100 mg orally or IV every 12 hours × 14 days
• Or: Cefotetan 2 g IV every 12 hours + Doxycycline 100 mg orally or IV every 12 hours
• Or: Ceftriaxone 1 g IV every 24 hours + Doxycycline 100 mg orally or IV every 12 hours ± Metronidazole 500 mg every 12 hours

• Clindamycin 900 mg IV every 8 hours + Gentamicin loading dose 2 mg/kg IV/IM, then 1.5 mg/kg every 8 hours

Why clindamycin + gentamicin? Clindamycin covers anaerobes and Gram-positive organisms; gentamicin covers Gram-negative facultative organisms including E. coli. Together they cover the polymicrobial spectrum of PID.

Oral Regimens — Outpatient (Mild-to-Moderate Disease)

• Levofloxacin 500 mg once daily × 14 days OR Ofloxacin 400 mg twice daily × 14 days
• ± Metronidazole 500 mg twice daily × 14 days (add if anaerobic coverage needed)

⚠️ Important 2025 update: A recent meta-analysis (PMID [41327742]) of fluoroquinolones in PID treatment found them effective but highlighted rising N. gonorrhoeae fluoroquinolone resistance. Fluoroquinolones should only be used after local resistance data confirm susceptibility or if cephalosporins cannot be used.

• Ceftriaxone 250 mg IM single dose + Doxycycline 100 mg twice daily × 14 days ± Metronidazole 500 mg twice daily × 14 days
• OR: Cefoxitin 2 g IM single dose + Probenecid 1 g orally concurrently + Doxycycline 100 mg twice daily × 14 days ± Metronidazole
• OR: Third-generation cephalosporin + Doxycycline ± Metronidazole

Why add probenecid with cefoxitin IM? Probenecid is a uricosuric agent that inhibits renal tubular secretion of cefoxitin, prolonging its serum half-life and increasing antibiotic tissue levels — maximizing efficacy of the single-dose IM administration.

Why metronidazole? Metronidazole covers anaerobic bacteria (which cause ~25–33% of PID cases) and also treats co-existing bacterial vaginosis, which is a risk factor for ascending infection.

If an IUD is in situ, it should be removed if clinical improvement does not occur within 72 hours.

Surgical Management

• Ruptured abscess with spread to peritoneum (peritonitis)
• Failure of medical treatment after 48–72 hours
• Abscess persists after 2–3 weeks with ongoing abdominal pain

10. Prevention & Public Health

Screening

• Annual chlamydia screening for all sexually active women ≤25 years
• Annual screening for sexually active women >25 with high-risk behavior
• Screen pregnant women in the first trimester

Rationale: Asymptomatic chlamydia is extremely common. Treating it before it ascends prevents PID and its long-term sequelae (infertility, ectopic pregnancy).

Partner Management

• All male sex partners of women with PID should be examined and treated empirically
• Male partners of women with gonorrhea or chlamydia-related PID are frequently asymptomatic but act as reservoirs for re-infection
• Treatment should cover both C. trachomatis and N. gonorrhoeae regardless of identified pathogen

Reporting

• Gonorrhea and chlamydia are reportable in all U.S. states
• PID itself is reportable in some states — check local mandates

Patient Education

• Explain nature and transmission of the infection
• Risk-reduction counseling (condom use, limiting partners)
• Individualized risk-reduction plans
• Importance of completing the full antibiotic course
• Partner notification and treatment

11. Summary Flowchart

Sexually active woman + pelvic/lower abdominal pain
              ↓
Pelvic exam: cervical motion tenderness, uterine/adnexal tenderness?
              ↓ YES
Exclude: ectopic pregnancy (β-hCG), appendicitis, ovarian torsion
              ↓
Collect cervical swabs (GC, Chlamydia); check WBC, CRP, ESR; pelvic US
              ↓
Hospitalization criteria met?
     YES → IV Cefoxitin + Doxycycline (± Clindamycin/Gentamicin)
     NO  → Oral Ceftriaxone IM + Doxycycline (± Metronidazole) × 14 days
              ↓
Review at 72 hours — no improvement?
     → Hospitalize / Consider laparoscopy / IUD removal
              ↓
Screen and treat partner; arrange follow-up