Chlamydia trachomatis and Neisseria gonorrhoea account for the majority of cases.
- in UK, chlamydia trachomatis is the most important cause of PID, being responsible for at least 50% of identified cases
- Neisseria gonorrhoea and chlamydia trachomatis co-infection can occur
Less commonly, PID may result from:
- Mycoplasma hominis
- Mycoplasma genitalium
- anaerobes such as Bacteroides
- G. vaginalis
- Haemophilus influenzae
- Cytomegalovirus
- U. urealyticum (2)
- Actinomyces israelii - especially with long term IUCD; may cause unilateral infection
- Herpes simplex virus type II - very rarely
No microbiological cause can be found in 20%.
Routes of infection include:
- ascending from the vagina - endogenous infection, for example, Bacteroides; or sexually transmitted infection, especially Chlamydia and Neiserria
- direct inoculation - for example, during dilatation and curettage, termination of pregnancy, insertion of a intrauterine contraceptive device
- transperitoneal - for example, following appendicitis or diverticulitis
- haematogenous - classically tuberculosis, usually at the time of puberty, but theoretically, any bacteraemia may produce pelvic foci of infection
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