Pelvic Inflammatory Disease

Pelvic inflammatory disease (PID) is defined as a polymicrobial infection of the upper female reproductive system. The disease can affect the uterus, fallopian tubes, ovaries, and adjacent structures. Pelvic inflammatory disease is closely linked with sexually transmitted diseases, most commonly caused by Chlamydia trachomatis and Neisseria gonorrhoeae, as well as organisms associated with bacterial vaginosis, such as Gardnerella vaginalis. Common symptoms are lower abdominal pain, cervical discharge, and irregular vaginal bleeding. Complications of PID can include ectopic pregnancy, chronic pelvic pain, and infertility. Diagnosis is primarily clinical in addition to PCR testing of cervical specimens and sometimes imaging or laparoscopy. Due to its polymicrobial nature, PID treatment is with combination antibiotic regimens.

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Pelvic inflammatory disease (PID) is an acute upper genital tract infection in women that affects the uterus, oviducts, ovaries, and possibly the adjacent pelvic organs.


  • Approximately 90,000 outpatient cases per year in the United States, including emergency department visits
  • More common in women < 35 years old
  • PID is rare before menarche. 
  • Risk factors:
    • Unprotected sexual intercourse
    • Multiple sexual partners
    • History of STIs
    • Presence of bacterial vaginosis (depending on the bacteria)
  • The overall incidence of sexually transmitted PID is decreasing because of Chlamydia screening in young women.


  • STIs (85%):
    • Chlamydia trachomatis (most common bacterial STI, which may be subacute and subclinical in presentation)
    • Neisseria gonorrhoeae
    • Mycoplasma genitalium
  • Other isolated bacteria: 
    • Haemophilus influenzae
    • Streptococcus agalactiae
    • Enteric gram-negative bacilli
    • Ureaplasma species
  • Post-operative peritonitis
  • Instrumentation or trauma-related pelvic infection
Chlamydia trachomatis inclusion bodies

Photomicrograph showcasing McCoy cell monolayers with Chlamydia trachomatis inclusion bodies

Image: “Chlamydia trachomatis inclusion bodies” by CDC/Dr. E. Arum. License: Public Domain


Normal pelvic protection

  • Endocervical canal serves as a barrier between the sterile upper genital tract and the vaginal canal, which contains different bacteria.
  • Normal vaginal flora is predominantly Lactobacillus spp. mixed with a low amount of potentially harmful bacteria.

Pelvic infection

  • Infection from STI or vaginal microorganisms (may be asymptomatic) → disruption of mucosal barrier → spread of infection to upper genital tract (usually symptomatic) → spread of infection to peritoneal cavity
  • Infection sites:
    • Cervix: cervicitis
    • Uterus/endometrium: endometritis
    • Fallopian tube: salpingitis
    • Ovaries: oophoritis
    • Surrounding area/peritoneum: peritonitis
  • Increased risk of PID from lower genital tract bacteria occurs:
    • During menses  
    • With an intrauterine device (IUD)
    • Due to poorly understood genetic or immune factors (affecting bacterial load and thickness of cervical mucus)
PID sites

Sites of infection in PID: cervix, endometrium/uterus, ovary, and fallopian tubes

Image: “PID-Sites” by BruceBlaus. License: Public Domain

Clinical Presentation

Signs and symptoms

  • Acute PID:
    • Fever 
    • Nausea and/or vomiting
    • Lower abdominal pain
    • Purulent vaginal discharge
    • Abnormal uterine bleeding
    • Dyspareunia
    • Dysuria
  • Subclinical PID:
    • Signs and symptoms can be mild, especially if due to C. trachomatis or M. genitalium.
    • Some patients present with infertility (from adhesions and distal tube occlusion from PID).
  • Chronic PID:
    • Indolent onset of fever, abdominal pain, and weight loss
    • Noted in actinomycosis and tuberculosis

Physical exam

  • Cervical discharge
  • Cervical motion tenderness
  • Guarding or rebound tenderness
  • Uterine and/or adnexal tenderness 
  • Adnexal mass


  • Tubo-ovarian abscess: presents as an adnexal mass
  • Ectopic pregnancy
  • Infertility
  • Hydrosalpinx 
  • Fitz-Hugh-Curtis syndrome (peri-hepatitis or inflammation of the liver capsule and peritoneal surfaces)

Diagnosis and Management


Diagnosis is primarily clinical with a high index of suspicion.

Laboratory tests:

  • CBC shows leukocytosis in 50% of patients.
  • Elevated inflammatory markers such as erythrocyte sedimentation rate (ESR) or CRP
  • Presence of > 10 WBCs per high-power field in vaginal discharge
  • PCR detection of N. gonorrhoeae and C. trachomatis
  • Cultures for causative organisms for PID
  • Additional STI tests: HIV, syphilis
  • Pregnancy test (to rule out ectopic pregnancy)


  • Transvaginal ultrasound if clinical and laboratory findings inconclusive or complications suspected
  • May show thickened fallopian tube, free pelvic fluid, or indistinct endometrial borders
  • In cases of tubo-ovarian abscess: complex adnexal collection with multiple fluid levels

Laparoscopic exploration:

  • Failed empiric treatment
  • History of PID with negative tests
  • Fitz-Hugh-Curtis syndrome
  • Tubo-ovarian abscess


  • Often, empiric antibiotic therapy with both outpatient and inpatient regimens aimed to cover aerobic and anaerobic infection
  • Main targets: C. trachomatis and N. gonorrhoeae
  • Outpatient management:
    • Long-acting cephalosporin (IM) + oral doxycycline (ceftriaxone 250 mg IM + doxycycline 100 mg oral twice a day x 14 days)
    • Add metronidazole if with Trichomonas vaginalis or bacterial vaginosis.
  • Inpatient management:
    • Cefotetan + doxycycline
    • Cefoxitin + doxycycline
    • Inpatient management indications:
      • Failed oral therapy
      • High fevers
      • Pregnancy
      • Tubo-ovarian abscess
      • If appendicitis or alternate diagnosis cannot be ruled out
  • Surgical:
    • Drain abscesses.
    • Exploratory laparoscopy needed in some cases to establish diagnosis
  • Pelvic rest
  • Patient education regarding safe sex practices and possible complications
Diagnosis of pelvic inflammatory disease

Pelvic inflammatory disease: grayscale ultrasound (A) and color Doppler (B) showing increased vascularity in the uterus (consistent with PID). Laparoscopy (C) confirms PID (uterine and adnexal swelling).

Image: “Pelvic inflammatory disease” by Department of Medical, Surgical and Neuro Sciences, Section of Radiological Sciences, Siena, Italy. License: CC BY 2.0

Differential Diagnosis

  • Ectopic pregnancy: implantation of fertilized egg outside of the uterus, often due to disruption in normal anatomy of the fallopian tube. Abdominal pain is a common symptom as the developing embryo grows. Diagnosis can be made with ultrasound and lab tests. Treatment can be expectant, medical, or surgical. 
  • Appendicitis: acute inflammation of the vermiform appendix. Classic symptoms are periumbilical pain that migrates to the right lower quadrant, anorexia, fever, nausea, and vomiting. Clinical diagnosis shows pain over McBurney’s point in the right lower quadrant. Ultrasound or CT can help establish the diagnosis. Treatment is surgical appendectomy but perforations, which can occur up to 20% of the time, may be managed nonoperatively with antibiotics.
  • Endometriosis: a common condition of implantation of endometrial tissue outside of the uterus, usually within the pelvis. Symptoms include pelvic pain that is worse around menses. The condition can lead to chronic pain, adhesions, and infertility. Diagnosis is clinical. Treatment includes oral contraceptive pills with progestin to suppress the inflammation. Surgery is sometimes needed to establish the diagnosis and remove implantations.
  • Ruptured ovarian cyst: most ovarian cysts are small and benign, but rupture can cause unilateral lower abdominal pain. Diagnosis is made by ultrasound. 
  • Nephrolithiasis: urinary calculi (stones) lead to pain, nausea, vomiting, and, possibly, fever and chills with infection. Diagnosis is by urinalysis and CT. Treatment can include pain relief, antibiotics, lithotripsy, and endoscopy.


  1. Goje, O. (2019). Pelvic Inflammatory Disease (PID). Retrieved February 1, 2021, from,-cervicitis,-and-pelvic-inflammatory-disease-pid/pelvic-inflammatory-disease-pid
  2. Ross, J., Chacko, M. (2020). Pelvic inflammatory disease: Clinical manifestations and diagnosis. Retrieved February 2, 2021, from
  3. Le T, Bhushan, V, Sochat, M, et al. (2020). First Aid for the USMLE 1, 30th ed.(p.185). McGraw-Hill.

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