What is pelvic inflammatory disease?

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PID is inflammation in the female upper reproductive tract caused by an infection. The female upper reproductive tract consists of the uterine body, fallopian tubes, ovaries, and pelvic peritoneum. Infections that cause PID generally start in the lower reproductive tract (i.e., the vagina or cervix) and spread to the upper reproductive tract.ⁱⁱ

PID is typically caused by sexually transmitted infections (STIs). The most common STIs related to PID are Neisseria gonorrhea and Chlamydia trachomatis. PID prevalence varies by age, with the highest rates consistently occurring among females between the ages of 16-24.ⁱⁱⁱ Barrier methods used to prevent STIs are thus similarly effective for PID prevention.

A 2017 study revealed a lifetime PID prevalence of 4.4 percent among sexually active women aged 18 to 44 within the United States.^iv The observed risk was largely associated with sexual activity behaviors, such as increased numbers of sexual partners and previous history of an STI. These authors also observed that the lifetime prevalence of PID was variable depending on socioeconomic factors.^v

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What are the symptoms of pelvic inflammatory disease?

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Doctors and researchers classify PID into three distinct categories, defined by the presentation and clinical course of the disease: acute (sudden onset), subclinical (no outwardly observable symptoms), or chronic (ongoing).

Acute PID symptoms include the acute onset of lower abdomen pain, severe pain in the pelvic area, foul-smelling or otherwise unusual vaginal discharge, painful sexual intercourse (dyspareunia), and abnormal vaginal bleeding. On physical examination, women with acute PID may exhibit lower abdominal tenderness when the lower abdomen or uterus is palpated by the examiner, and/or pain with movement of the cervix during an internal vaginal examination.^vi Internal assessment of the cervix and other pelvic organs is done using a technique called bimanual examination, in which the practitioner inserts two fingers into the patient's vagina and uses the other hand to press on the lower abdomen to palpate the upper reproductive tract organs to assess for masses or tenderness. Patients with acute PID may also present with chills and a high fever above 38 degrees C.^vii

One severe complication of PID is the development of a tubo-ovarian abscess (TOA). This area of inflammation includes a collection of pus, and it forms a mass that involves both the fallopian tube and ovary. TOA may be suspected when a patient has more severe symptoms, or when the mass is palpated during a physical exam in patients with PID. It is diagnosed either with pelvic ultrasound or computed tomography (CT) imaging of the pelvis.^viii Patients with PID that involve a TOA should be hospitalized to begin intravenous antibiotic treatment with close monitoring for clinical improvement. A minimally invasive drain may be considered for larger TOAs or if the patient does not improve with intravenous antibiotics.^ix

Subclinical PID presents with minimal to no symptoms, even though there is active inflammation and infection within the upper reproductive tract. Subclinical PID can still result in adverse long-term consequences.^x Because asymptomatic cases do not present for evaluation, PID is often only diagnosed in those cases when scar tissue is identified around the organs of the upper genital tract at the time of abdominal surgery.  

Chronic PID refers to PID due to Mycobacterium tuberculosis or actinomyces species with symptoms lasting longer than 30 days at the time of presentation.^xi Symptoms of chronic PID may include chronic pelvic pain, abnormal vaginal discharge, and pain with intercourse.

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What causes pelvic inflammatory disease?

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As noted previously, PID is most commonly caused by STIs, with most cases arising from chlamydia and gonorrhea, though other STIs such as Mycoplasma genitalum and Trichomonas vaginalis (bacterial and parasitic infections) can be the source of PID.^xii

PID caused by gonorrhea tends to be more severe than PID caused by chlamydia. A study of 4 819 patients with PID found that patients with gonorrhea had an 85 percent chance of hospitalization, while for patients with chlamydia that number was 43 percent. Patients testing positive for both chlamydia and gonorrhea had an 87 percent chance of hospitalization.^xiii

While less common, PID can also be caused by the bacteria associated with bacterial vaginosis (BV).^xiv BV is not an STI but is rather a type of vaginal inflammation caused by overgrowth of bacteria that exist naturally in the vagina. Certain microorganisms that can cause BV are also associated with a significantly increased risk of PID.^xv In addition, another less frequent cause of PID includes infection of the lower reproductive tract by respiratory or enteric (intestinal) pathogens.

Multiple factors put patients at an increased risk for PID, including:^xvi

• Sexual behaviours that increase the risk of STIs, including having unprotected sex, multiple sex partners, a new sexual partner within three months, a personal history of an STI, or a partner with a history of an STI.
• Procedures that involve placing an instrument through the cervix and into the uterine cavity, including a dilation and curettage, hysteroscopy, hysterosalpingography, or insertion of an intrauterine device (IUD). The use of sterile instruments significantly decreases the risk of infection following these procedures.

While these factors increase the risk of PID, that does not mean that STI infections, or infections after procedures, will always lead to PID.

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How is pelvic inflammatory disease diagnosed?

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Doctors usually diagnose PID by performing a thorough medical history and physical examination. Sensitivity of clinical diagnosis for PID is approximately 87 percent, meaning the likelihood of a false negative is low.^xvii

Doctors will diagnose PID in the absence of other causes of pelvic pain in at-risk females with unexplained pelvic pain and cervical, uterine, or ovarian (adnexal) tenderness on bimanual examination.^xviii An at-risk woman is a person who is sexually active or at an increased risk of having an STI. In this subset of patients, treatment may be initiated based on clinical findings alone.^xix This low threshold to diagnose and treat PID based on clinical symptoms and examination findings is chosen because early treatment with antibiotics can prevent severe consequences of PID. Further, PID can still occur when STI testing is negative. Therefore, laboratory testing alone should not be used to diagnose PID and/or to determine whether to initiate antibiotic treatment.

If there is no pain upon examination, routine STI testing and additional testing is often recommended. Pregnancy tests are also advised before diagnosing PID in order to rule out a normal (intrauterine) or ectopic pregnancy.^xx

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How does pelvic inflammatory disease impact fertility?

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Pelvic inflammatory disease may negatively affect female fertility. It most often leads to a condition known as tubal factor infertility (TFI), which may cause scarring, inflammation, and damage of the fallopian tubes, all of which may interfere with the normal tubal function of sperm, oocyte, and embryo transport. Studies suggest 15 to 19 percent of patients with PID develop tubal factor infertility, and multiple episodes of PID increase the risk of developing this type of infertility.^xxi,xxii

Of the bacteria associated with PID, chlamydia infection has the greatest risk of infertility. This may be due to the inflammatory immune response against Chlamydia trachomatis that occurs in the fallopian tubes during infection.^xxiii

Subclinical PID has also been shown to have adverse effects on fertility. In a study of 418 women, those with subclinical PID had a 40 percent reduced incidence of pregnancy compared to those without PID.^xxiv A 2019 study of 121 800 pregnant women (30 450 PID patients and 91 350 matched controls) showed that PID also confers a higher risk of ectopic pregnancy.^xxv Women with PID were just over twice as likely to develop ectopic pregnancy compared to those without PID.^xxvi

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What are the treatment options for PID and how successful are they?

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Patients with PID are treated with antibiotics, most commonly with a combination of ceftriaxone, doxycycline, and metronidazole.^xxvii Ceftriaxone is usually given as a single dose intramuscularly, while doxycycline and metronidazole are typically given orally for at least 14 days.^xxviii Men who have had sexual contact with a patient with PID in the past 60 days should also be evaluated and treated for possible STIs.^xxix

More severe cases may require hospitalization for administering IV antibiotics, and in more rare cases, for abdominal surgery. The decision to admit a patient to the hospital usually occurs when one of the following conditions is present: pregnancy, surgical emergency, tubo-ovarian abscess, nausea and vomiting with a temperature above 38.5C (101F), or when an oral antibiotic regimen is not working.^xxx

Early PID treatment may help reduce the risk of long-term complications or serious adverse effects associated with PID. Women should call a doctor as soon as possible after noticing any unusual symptoms.

Since PID can lead to fallopian tube damage, patients who have had pelvic inflammatory disease have an increased risk of infertility and in these cases often need help to achieve pregnancy. Tubal factor infertility is most often treated by in vitro fertilization (IVF), which completely bypasses the fallopian tubes. According to the latest national summary data reported by the US Society for Assisted Reproductive Technology (SART),^xxxi patients with tubal infertility have a good chance of achieving pregnancy via IVF, with a 44.3 percent cumulative live birth rate per IVF cycle (for women under 35yr). For comparison, this rate is 41.4 percent in women with other non-tubal factor infertility.^xxxii

In select cases, doctors will use surgery to treat patients with tubal factor infertility. Tubal surgery involves the removal of scar tissue and blockages in or around the fallopian tubes.^xxxiii The decision to use tubal surgery must be balanced against the baseline risks of undergoing the surgical procedure. For older patients or those with severe scar tissue around the fallopian tubes, the chance of a successful tubal correction surgery leading to an unassisted pregnancy is generally low and IVF is the preferred treatment in these cases.

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What are the other pelvic inflammatory disease risks/conditions?

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PID can lead to several other health risks and possible complications in addition to female infertility. These include:  

• Recurrent PID: A clinical trial known as the PEACH (PID Evaluation and Clinical Health) study found that 21.3 percent of women treated for mild to moderate PID experienced recurrence at 84 months follow-up. PID recurrence was associated with an increased risk of infertility.^xxxiv This can occur if the initial infection was not completely treated or if infection with a new STI or other PID-causing pathogen occurs.
• Chronic pelvic pain: The PEACH study also found that 42 percent of these patients treated for PID went on to develop chronic pelvic pain at follow-up.^xxxv
• Hydrosalpinx: hydrosalpinx is the accumulation of fluid within and enlargement of the fallopian tubes. Hydrosalpinx can contribute to tubal factor infertility, which can have negative consequences on pregnancy rates and outcomes.^xxxvi

Given the potential for severe outcomes, taking steps to prevent PID is important for all sexually active women. Patients are encouraged to practice safe sex with barrier protection and get tested (along with any partners) for sexually transmitted infections regularly.  

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Conclusion

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Pelvic inflammatory disease can affect women of all ages, but most commonly occurs among women who are at increased risk for contracting a sexually transmitted infection. It is most often caused by STIs but can also be caused by non-sexually transmitted reproductive tract infections.

Anyone experiencing PID symptoms or concerns about their health should contact their health care provider. PID can lead to long-term health problems including infertility and chronic pelvic pain, but prompt treatment may help avoid these complications.