Pelvic inflammatory disease (PID)

Summary

Pelvic inflammatory disease (PID) is a polymicrobial infection of the upper female genital tract, most often caused by Chlamydia trachomatis or Neisseria gonorrhoeae. It typically follows ascending infection from the lower genital tract and can lead to infertility, ectopic pregnancy, and chronic pelvic pain. Risk factors include multiple partners, unprotected sex, age < 35, prior STIs, and recent IUD insertion. Symptoms include lower abdominal pain, fever, abnormal discharge, and cervical motion tenderness. Diagnosis is mainly clinical, supported by STI testing and imaging. Treatment is prompt empiric antibiotics—outpatient regimens combine ceftriaxone, doxycycline, and metronidazole; severe cases require inpatient IV therapy, with possible surgical drainage for tubo-ovarian abscess. Partner treatment and sexual abstinence during therapy are essential.

Definition

 Pelvic inflammatory disease (PID) is a polymicrobial infection of the upper female genital tract, involving the uterus (endometritis), fallopian tubes (salpingitis, pyosalpinx, tubo-ovarian abscess), ovaries (oophoritis), parametrium (parametritis), and/or pelvic peritoneum (peritonitis). It most commonly results from ascending infection from the cervix or vagina, typically following disruption of the cervical barrier.

Epidemiology

• Lifetime prevalence: ~4.5% in women aged 18–44 years.

• PID is a major cause of tubal factor infertility, ectopic pregnancy, and chronic pelvic pain.

Etiology

Common pathogens:

• Chlamydia trachomatis (most common)

• Neisseria gonorrhoeae (second most common)

Other possible organisms:

• Escherichia coli, Mycoplasma genitalium, Ureaplasma urealyticum, anaerobes, Gardnerella vaginalis.

• Intrauterine device (IUD) use increases PID risk primarily in the first 3 weeks post-insertion.

Risk factors:

• Multiple sexual partners, unprotected intercourse

• Age < 35 years, nulliparity

• Prior STIs or adnexitis

• Vaginal dysbiosis

Protective factors:

• Barrier contraception, oral contraceptive pills, progestogen-only methods

Pathophysiology

An initial lower genital tract infection (cervicitis, vaginitis) allows pathogenic organisms to ascend into the upper genital tract, triggering inflammation and tissue damage. Chronic or untreated infection leads to tubal scarring, adhesions, and loss of ciliary function, predisposing to infertility and ectopic pregnancy.

Clinical Features

• Bilateral lower abdominal or pelvic pain (may progress to acute abdomen)

• Fever, chills

• Abnormal vaginal discharge (often mucopurulent)

• Dyspareunia, postcoital bleeding

• Menorrhagia or metrorrhagia

• Dysuria or urinary urgency

• Cervical motion tenderness, uterine tenderness, adnexal tenderness on examination

Complications

Acute:

• Sepsis

• Tubo-ovarian abscess (TOA)

• Peritonitis

• Fitz-Hugh–Curtis syndrome (FHCS): Perihepatitis with right upper quadrant pain, often radiating to the shoulder, caused by adhesions between the liver capsule and abdominal wall.

Chronic:

• Tubal factor infertility

• Ectopic pregnancy

• Chronic pelvic pain

• Hydrosalpinx

Diagnosis

Approach:
PID is primarily a clinical diagnosis. Maintain a low threshold in sexually active women with pelvic or lower abdominal pain and no other clear cause.

Minimum diagnostic criteria (in a sexually active woman with pelvic pain):

• Cervical motion tenderness

• Uterine tenderness

• Adnexal tenderness

Supportive findings criteria:

• Oral temperature > 38.3°C

• Mucopurulent cervical discharge or cervical friability

• Abundant WBCs on vaginal microscopy

• Elevated ESR/CRP

• Positive NAAT for C. trachomatis or N. gonorrhoeae

Investigations:

• Pregnancy test (to exclude ectopic pregnancy)

• STI testing (NAAT for chlamydia/gonorrhea)

• Pelvic ultrasound (to exclude TOA or other pathology)

• Laparoscopy: gold standard, but reserved for unclear or refractory cases.

Management

General principles:

• Initiate empiric broad-spectrum antibiotics promptly when PID is suspected—do not delay for microbiological confirmation.

• Treat sexual partners from the past 60 days for chlamydia and gonorrhea.

• Advise abstinence until therapy is completed and partners are treated.