Pelvic inflammatory disease - Causes of pelvic inflammatory disease

Pelvic inflammatory disease (PID) is an infection. If a woman develops an infection in her vagina, the bacteria causing the infection can move upwards through the cervix (the entrance to the womb) into the womb and spread to the 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 bacteria are responsible. Therefore, a combination of antibiotics may be prescribed so that a variety of bacteria can be treated.

Chlamydia and gonorrhoea

Many different types of bacteria can cause PID. However, the most frequent causes are two common sexually transmitted infections (STIS): chlamydia and gonorrhoea.

In the UK, the bacteria that cause chlamydia (Chlamydia trachomatis) are responsible for 50-65% of cases of PID. The bacteria that cause gonorrhoea (Neisseria gonorrhoeae) are responsible for about 14% of cases. About 8% of women with PID are infected with both chlamydia and gonorrhoea.

Other causes

Sometimes, the infection that leads to PID may start as a result of bacteria introduced into the vagina or upper genital tract during childbirth, an abortion or miscarriage, or a procedure to take a sample of tissue from the inside of the womb (endometrial biopsy).

In rare cases, PID can develop as a result of appendicitis, treatment following an abnormal cervical smear test or after the fitting of an intrauterine device (IUD).

In some cases, the cause of the infection that leads to PID is unknown. Such cases may be the result of normally harmless bacteria found in the vagina. These bacteria can sometimes get past the cervix and into the reproductive organs. Although harmless to the vagina, these types of bacteria can cause infection in other parts of the body. Infection in this way is most likely to happen when there has been damage to the cervix, or if you have had PID before.