Pelvic Inflammatory Disease (PID)

Introduction

Pelvic inflammatory disease (PID) is the inflammation of the upper female genital tract that usually arises from an ascending infection from the endocervix. PID can affect the uterus, fallopian tubes, and ovaries.

An estimated 1 in 1000 women aged between 15 and 34 are diagnosed with PID every year.

Aetiology

PID can be caused by sexually transmitted infections, including:

• Chlamydia trachomatis (most common, accounts for 14-35% of PID cases)
• Neisseria gonorrhoea
• Mycoplasma genitalium

PID can also be caused by non-sexually transmitted bacteria that can be part of the normal vaginal flora, such as Gardnerella vaginalis and other anaerobic bacteria.

Risk factors

Risk factors for PID include:

• Young age, especially <25
• Multiple or new partners
• Previous history of a sexually transmitted infection or PID
• Not using condoms during sex
• Instrumentation of the uterus (e.g. abortions, gynaecological procedures such as endometrial biopsies, intrauterine device fitting)

Clinical features

History

Typical symptoms of PID include:

• Lower abdominal pain, which can be bilateral or unilateral
• Pain during penetrative sex (deep dyspareunia)
• Menstrual changes, such as bleeding after sex (post-coital bleeding), bleeding between periods (inter-menstrual bleeding) and heavy bleeding (menorrhagia)
• Abnormal vaginal discharge

Other important areas to cover in the history include:

• Menstrual history (e.g. first day of last menstrual period)
• Sexual history (e.g. when did the patient last have unprotected sexual intercourse, previous sexually transmitted infections etc.)

Clinical examination

If PID is suspected, abdominal, speculum, and bimanual examinations are required. Microscopy can also be considered if suspecting Neisseria gonorrhoea.

Patients with severe symptoms should have a set of basic observations (vital signs) recorded. Severe PID may cause a fever. 

Typical findings on abdominal examination may include:

• Abdominal tenderness (unilateral or bilateral)
• Guarding
• Peritonism & rebound tenderness: in cases of severe PID

Speculum examination may show mucopurulent cervicitis (pustular discharge from the cervix).

Typical findings on bimanual examination may include:

• Cervical motion tenderness
• Adnexal tenderness (unilateral or bilateral)
• Palpable mass (if a tubo-ovarian abscess has formed)

Differential diagnoses

Differential diagnoses to consider in the context of PID include:

• Ectopic pregnancy
• Urinary tract infection
• Acute appendicitis
• Diverticulitis
• Endometriosis
• Complications of an ovarian cyst (e.g. torsion or rupture)

Investigations

Bedside investigations

Relevant bedside investigations include:

• Pregnancy testing: to rule out an ectopic pregnancy
• Urinalysis: to exclude urinary tract infection

Laboratory investigations

Relevant laboratory investigations include:

• Vaginal swabs: chlamydia, gonorrhoea and mycoplasma genitalium nucleic acid amplification technique (NAAT)
• MC&S swab of cervical discharge (for gonorrhoea culture, but will also detect other bacteria)
• Routine HIV and syphilis testing

Patients admitted to hospital with PID will have routine blood tests, including a full blood count (neutrophilia) and inflammatory markers (raised CRP). 

Imaging

A transvaginal ultrasound scan can be performed to exclude ovarian pathology, free fluid in the pelvis or if there is suspicion of a tubo-ovarian abscess. A pyosalpinx is the presence of pus in the fallopian tube. Salpingitis is an infection in the tube.

Ultrasound is also helpful when considering other diagnoses (e.g. ectopic pregnancy in the context of a positive pregnancy test).

Diagnosis

There is no single test to diagnose PID. The diagnosis is based on clinical judgement according to clinical features, risk factors and consideration of other differential diagnoses. A negative STI screen does not rule out PID.

There is a low threshold for diagnosis as the consequences of delaying treatment can have significant complications.

Management

PID is managed with antibiotics. The type of antibiotics used and the route of administration depend on the severity of the illness. The antibiotic regimen is designed to cover chlamydia, gonorrhoea, and anaerobic bacteria.

The first line treatment does not cover Mycoplasma genitalium; a subsequent positive result for mycoplasma may need treatment with moxifloxacin.

Patients should be advised to use regular analgesia and abstain from sexual contact until the antibiotic course has been completed (usually two weeks) and their partner has also completed their course of antibiotics.

Outpatient management

First line outpatient antibiotic treatment is:

• 1g intramuscular ceftriaxone single dose
• 100mg oral doxycycline twice daily for fourteen days
• 400mg oral metronidazole twice daily for fourteen days

Second line outpatient antibiotic treatment is:

• 400mg oral ofloxacin twice daily for fourteen days PLUS 400mg oral Metronidazole twice daily for fourteen days OR
• 400mg oral moxifloxacin once daily for fourteen days

Inpatient management

Inpatient management is reserved for patients with systemic illness, no response to outpatient management, intolerance to outpatient management (e.g. vomiting), or evidence of a tubo-ovarian abscess.

First line inpatient antibiotic treatment is:

• 2g intravenous ceftriaxone once daily
• 100mg intravenous OR oral doxycycline twice daily for fourteen days
• 400mg oral metronidazole twice daily for fourteen days

Intravenous therapy should be continued for 24 hours after clinical improvement. The patient can then switch to oral therapy.

Follow up

Clinical symptoms should improve within 72 hours of treatment. If symptoms have not improved, consider arranging further investigations, switching to inpatient treatment or making an alternative diagnosis

A test of cure is required: 

• If positive for chlamydia, a repeat test is recommended 3 to 5 weeks after completing treatment if the patient is still experiencing symptoms or you suspect poor treatment compliance
• If positive for gonorrhoea, a test of cure is recommended 2 weeks after completing treatment
• If positive for mycoplasma genitalium, a test of cure is recommended 5 weeks after completing treatment

Complications

If left untreated, PID can have several long-term complications including:

• Chronic pelvic pain (even after treatment)
• Increased risks of future ectopic pregnancies
• Subfertility (due to scarring caused by infections)
• Abscesses in the ovaries and fallopian tubes (tubo-ovarian abscess) and pus (pyosalpinx) or fluid (hydrosalpinx) in the fallopian tubes

Key points

• Pelvic inflammatory disease is an upper genital infection caused by a spreading infection from the endocervix
• This can be caused by sexually transmitted infections as well as normal bacteria found in the vagina
• Risk factors include young age, multiple or new partners, not using condoms and a history of previous sexually transmitted infections or PID
• PID can be asymptomatic, or patients can present with abdominal pain, pain during sex, abnormal vaginal discharge, or abnormal bleeding patterns.
• Clinical signs include a tender abdomen, cervical excitation, and adnexal tenderness
• Routine investigations should include vaginal swabs for bacterial sexually transmitted infections
• Treatment of PID is with a combination of antibiotics; early antibiotic treatment is important to reduce the risk of complications
• Complications of untreated PID can include long-term pelvic pain, subfertility and abscesses

Reviewer

Dr Najia Aziz

Consultant in Sexual and Reproductive Health

Editor

Dr Chris Jefferies

References

1. British Association of Sexual Health and HIV. United Kingdom National Guideline for the Management of Pelvic Inflammatory Disease (2019 Interim Update) Available from: LINK
2. Oxford University Press. Oxford Handbook of Genitourinary Medicine, HIV, And Sexual Health. 3^rd edition.