Polymicrobial ascending infection of the upper female genital tract — empiric treatment with low threshold to prevent sequelae.
Also known as: PID, salpingitis, endometritis, tubo-ovarian abscess, TOA
Overview
Infection and inflammation of the upper female genital tract including any combination of endometritis, salpingitis, oophoritis, tubo-ovarian abscess, and pelvic peritonitis, typically caused by ascending sexually transmitted organisms.
Epidemiology
~1 million US cases/year. Most common in sexually active women 15-25 years old. A major preventable cause of infertility, ectopic pregnancy, and chronic pelvic pain.
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Prior PID or STI (especially gonorrhea or chlamydia)
Inconsistent barrier contraception
Intrauterine procedure within 3 weeks (IUD insertion, endometrial biopsy)
Bacterial vaginosis
Pathophysiology
Cervical pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium) ascend through the endocervical canal to the upper tract, disrupting the cervical mucus barrier. Subsequent polymicrobial infection with anaerobes (Bacteroides, Peptostreptococcus), aerobes (E. coli, streptococci), and genital tract flora produces tubal inflammation, abscess formation, and scarring.
Clinical presentation
Symptoms
Lower abdominal/pelvic pain (often bilateral)
Abnormal vaginal discharge
Intermenstrual or postcoital bleeding
Dyspareunia
Fever, chills, nausea (variable)
Many cases are mild or subclinical — silent PID
Signs / physical exam
Cervical motion tenderness, uterine tenderness, or adnexal tenderness on bimanual exam
Mucopurulent cervical discharge or friability
Fever >38.3°C (101°F)
Right upper quadrant tenderness suggests Fitz-Hugh-Curtis syndrome (perihepatitis)
Classic findings
Sexually active young woman with bilateral lower abdominal pain, cervical motion tenderness, and mucopurulent cervical discharge.
Differential diagnosis
Ectopic pregnancy — Always check hCG; unilateral pain, vaginal bleeding, possible adnexal mass
Appendicitis — RLQ migration, anorexia, McBurney point tenderness; CT scan
Ovarian torsion — Sudden severe unilateral pain, nausea/vomiting; Doppler ultrasound
Ruptured ovarian cyst — Sudden pain, may have small free fluid; ultrasound
CDC minimum criteria (initiate empiric therapy if any one is present in a sexually active young woman with pelvic pain and no other cause): cervical motion tenderness, uterine tenderness, OR adnexal tenderness. Additional supportive criteria: oral temperature >38.3°C, abnormal cervical discharge, leukocytes on wet mount, elevated ESR/CRP, lab-confirmed GC or chlamydia.
Labs
Pregnancy test
Nucleic acid amplification tests for Neisseria gonorrhoeae and Chlamydia trachomatis (cervical or urine)
Wet mount of vaginal secretions: leukocytes confirm inflammation, identify BV/trichomonas
HIV and syphilis testing
CBC (leukocytosis), CRP/ESR (elevated)
Urinalysis
Imaging
Transvaginal ultrasound — if TOA suspected (severe pain, palpable mass, systemic illness, or no response to therapy)
CT scan — alternative diagnosis (appendicitis) or complicated disease
Laparoscopy — gold standard but rarely required; reserved for diagnostic uncertainty or failed therapy
Diagnostic algorithm
flowchart TD
A[Sexually active woman<br/>with pelvic pain] --> B[hCG, pelvic exam,<br/>GC/CT, urinalysis]
B --> C{CMT, uterine, or<br/>adnexal tenderness?}
C -->|Yes| D[Empiric PID treatment]
D --> E{Inpatient criteria?<br/>Pregnancy, TOA, severe,<br/>cannot tolerate PO}
E -->|No| F[Outpatient: ceftriaxone IM<br/>+ doxycycline + metronidazole<br/>× 14 days]
E -->|Yes| G[Inpatient IV antibiotics]
G --> H[Pelvic ultrasound:<br/>TOA?]
H -->|Yes| I[IV abx ± drainage<br/>if >7 cm or refractory]
F --> J[Reassess 48-72 h]
J -->|Improving| K[Complete 14-d course<br/>treat partners<br/>retest at 3 mo]
J -->|Not improving| L[Hospitalize, image,<br/>reconsider diagnosis]
PID management pathway — low threshold to treat empirically; escalate based on severity.
Treatment
First-line
Outpatient regimen (CDC 2021): ceftriaxone 500 mg IM × 1 + doxycycline 100 mg PO BID × 14 days + metronidazole 500 mg PO BID × 14 days
Inpatient indications: pregnancy, severe illness, TOA, failure of outpatient therapy, inability to tolerate PO, surgical emergency cannot be excluded
Inpatient regimen: cefoxitin 2 g IV q6h or cefotetan 2 g IV q12h PLUS doxycycline 100 mg IV/PO q12h (transition to oral doxycycline + metronidazole × 14 days total)
Alternative IV: clindamycin + gentamicin (especially for TOA)
Tubo-ovarian abscess
IV antibiotics with anaerobic coverage (clindamycin + gentamicin or ampicillin-sulbactam + doxycycline)
Image-guided drainage if abscess >7-9 cm, no response in 48-72 h, or clinical deterioration
Surgical drainage/oophorectomy if rupture suspected (acute abdomen, sepsis)
Pregnancy
Hospitalize
IV antibiotics; avoid doxycycline if possible — use azithromycin alternative
Maternal-fetal medicine and infectious disease consultation
Second-line / adjunct
Treat all sexual partners from previous 60 days for GC/CT
Abstinence until both treated and asymptomatic
Re-test for GC/CT 3 months after treatment (high re-infection rate)
Do NOT routinely remove IUD — leave in place if clinically improving
Complications
Infertility (12% after first episode, ~50% after three)
Ectopic pregnancy (6-10x risk)
Chronic pelvic pain
Tubo-ovarian abscess and rupture (life-threatening)
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