Pelvic inflammatory disease (PID) is caused by an infection developing in the female upper genital tract.

In most cases, the condition is caused by a bacterial infection spreading from the vagina or cervix (entrance to the womb) into the womb, fallopian tubes and ovaries.

PID is often caused by more than one type of bacterium and it can sometimes be difficult for doctors to pinpoint which are responsible.

This means a combination of antibiotics will be prescribed so a variety of bacteria can be treated.

Sexually transmitted infections (STIs)

In about 1 in 4 cases, PID is caused by a sexually transmitted infection (STI) such as chlamydia, gonorrhoea or mycoplasma genitalium.

These bacteria usually only infect the cervix, where they can be easily treated with a single dose of an antibiotic. 

But if they're not treated there's a risk the bacteria could travel into the upper genital tract.

It's estimated 1 in 10 women with untreated chlamydia may develop PID within a year.

Other causes

In many cases, the cause of the infection that leads to PID is unknown.

Sometimes normally harmless bacteria found in the vagina can get past the cervix and into the reproductive organs.

Although harmless in the vagina, these types of bacteria can cause infection in other parts of the body.

This is most likely to happen if:

• you have had PID before
• there's been damage to the cervix following childbirth or a miscarriage
• you have a procedure that involves opening the cervix (such as an abortion, inspection of the womb, or insertion of an intrauterine contraceptive device)

Which areas can become infected?

If an infection spreads upwards from the vagina and cervix, it can cause inflammation of the:

• womb lining (endometrium)
• fallopian tubes
• tissue around the womb
• ovaries
• lining of the inside of the abdomen (peritoneum)

Pockets of infected fluid called abscesses can also develop in the ovaries and fallopian tubes.

Who's most at risk?

Any woman can get PID, but you're more likely to get it if you:

• have more than 1 sexual partner
• have a new sexual partner
• have a history of STIs
• have had PID in the past
• are under 25
• started having sex at a young age

There's no single test for diagnosing pelvic inflammatory disease (PID). It's diagnosed based on your symptoms and a gynaecological examination.

Your doctor will first ask about your medical and sexual history.

The next step is to carry out a pelvic examination to check for any tenderness and abnormal vaginal discharge.

You may experience some discomfort during this examination, particularly if you do have PID.

Swabs are usually taken from the inside of your vagina and cervix. These are sent to a laboratory to look for signs of a bacterial infection and identify the bacteria responsible.

A positive test for chlamydia, gonorrhoea or mycoplasma genitalium supports the diagnosis of PID.

But most women have negative swabs and this doesn't rule out the diagnosis.

As PID can be difficult to diagnose, other tests may also be required to look for signs of infection or inflammation, or rule out other possible causes of your symptoms.

These tests may include:

• a urine or blood test
• a pregnancy test
• an ultrasound scan, which is usually carried out using a probe passed through the vagina (transvaginal ultrasound)

In some cases, laparoscopy (keyhole surgery) may be used to diagnose PID.

A laparoscopy is a minor operation where 2 small cuts are made in the abdomen.

A thin camera is inserted so the doctor can look at your internal organs and, if necessary, take tissue samples.

This is usually only done in more severe cases where there may be other possible causes of the symptoms, such as appendicitis.

Admission to hospital

You may be urgently admitted to hospital if:

• you're pregnant (especially if there's a chance you may have an ectopic pregnancy)
• your symptoms are severe (such as nausea, vomiting and a high fever)
• you have signs of pelvic peritonitis
• an abscess is suspected
• you're unable to take oral antibiotics and need to be given them through a drip (intravenously)
• you may need emergency surgery, such as for appendicitis

If it's diagnosed at an early stage, pelvic inflammatory disease (PID) can be treated easily and effectively with antibiotics.

These can be prescribed by your GP or a doctor at a sexual health clinic.

But left untreated, it can lead to more serious long-term complications. 

Find out more about the complications of PID

Antibiotics

Treatment with antibiotics needs to be started quickly, before the results of the swabs are available.

PID is usually caused by a variety of different bacteria, even in cases where chlamydia, gonorrhoea or mycoplasma genitalium is identified.

This means you'll be given a mixture of antibiotics to cover the most likely infections.

Tell your doctor if you think you may be pregnant before starting antibiotic treatment, as some antibiotics should be avoided during pregnancy.

You'll usually have to take the antibiotic tablets for 14 days, sometimes beginning with a single antibiotic injection. 

It's very important to complete the entire course of antibiotics, even if you're feeling better, to help ensure the infection is properly cleared.

In particularly severe cases of PID, you may have to be admitted to hospital to receive antibiotics through a drip in your arm (intravenously).

If you have pain around your pelvis or tummy, you can take painkillers such as paracetamol or ibuprofen while you're being treated with antibiotics.

Follow-up

In some cases, you may be advised to have a follow-up appointment 3 days after starting treatment so your doctor can check if the antibiotics are working.

If the antibiotics seem to be working, you may have another follow-up appointment at the end of the course to check if treatment has been successful.

If your symptoms haven't started to improve within 3 days, you may be advised to attend hospital for further tests and treatment.

If you have an intrauterine device (IUD) fitted, you may be advised to have it removed if your symptoms haven't improved within a few days, as it may be the cause of the infection.

Treating sexual partners

Any sexual partners you have been with in the 6 months before your symptoms started should be tested and treated to stop the infection recurring or being spread to others, even if no specific cause is identified.

PID can occur in long-term relationships where neither partner has had sex with anyone else.

It's more likely to return if both partners aren't treated at the same time.

You should avoid having sex until both you and your partner have completed the course of treatment.

If you haven't had a sexual partner in the previous 6 months, your most recent partner should be tested and treated.

Your doctor or sexual health clinic can help you contact your previous partners.

This can usually be done anonymously if you prefer.

Pelvic inflammatory disease (PID) can sometimes lead to serious and long-term problems, particularly if the condition isn't treated with antibiotics quickly.

But most women with PID who complete their course of antibiotics have no long-term problems.

Repeated episodes of PID

Some women experience repeated episodes of PID. This is known as recurrent pelvic inflammatory disease.

The condition can return if the initial infection isn't entirely cleared.

This is often because the course of antibiotics wasn't completed or because a sexual partner wasn't tested and treated.

If an episode of PID damages the womb or fallopian tubes, it can become easier for bacteria to infect these areas in the future, making it more likely that you'll develop the condition again.

Repeated episodes of PID are associated with an increased risk of infertility.

Abscesses

PID can sometimes cause collections of infected fluid called abscesses to develop, most commonly in the fallopian tubes and ovaries.

Abscesses may be treated with antibiotics, but sometimes laparoscopic surgery (keyhole surgery) may be needed to drain the fluid away.

The fluid can also sometimes be drained using a needle that's guided into place using an ultrasound scan.

Long-term pelvic pain

Some women with PID develop long-term (chronic) pain around their pelvis and lower abdomen, which can be difficult to live with and lead to further problems, such as depression and difficulty sleeping (insomnia).

If you develop chronic pelvic pain, you may be given painkillers to help control your symptoms.

Tests to determine the cause may be carried out.

If painkillers don't control your pain, you may be referred to a pain management team or a specialist pelvic pain clinic.

Ectopic pregnancy

An ectopic pregnancy is when a fertilised egg implants itself outside of the womb, usually in one of the fallopian tubes.

If PID infects the fallopian tubes, it can scar the lining of the tubes, making it more difficult for eggs to pass through.

If a fertilised egg gets stuck and begins to grow inside the tube, it can cause the tube to burst, which can sometimes lead to severe and life-threatening internal bleeding.

If you're diagnosed with an ectopic pregnancy, you may be given medication to stop the egg growing or have surgery to remove it.

Infertility

As well as increasing your risk of having an ectopic pregnancy, scarring or abscesses in the fallopian tubes can make it difficult for you to get pregnant if eggs can't pass easily into the womb.

It's estimated about 1 in 10 women with PID become infertile as a result of the condition, with the highest risk for women who delayed treatment or had repeated episodes of PID.

But a long-term study in the US showed that women who'd been successfully treated for PID had the same pregnancy rates as the rest of the population.

Blocked or damaged fallopian tubes can sometimes be treated with surgery.

If this isn't possible and you want to have children, you may want to consider an assisted conception technique, such as IVF.

IVF involves surgically removing eggs from a woman's ovaries and fertilising them with sperm in a laboratory, before planting the fertilised eggs into the woman's womb.

This technique can help you get pregnant if you can't have children naturally. But the success rate is often low, depending on your age and other factors.