Epidemiology

• among women aged 15 to 49 years, the estimated global prevalence of chlamydia was 3.4%, gonorrhoea was 2%, and trichomoniasis was 4.0% (1)
• PID is almost always caused by a sexually transmitted infection (STI) (2)
  • Chlamydia trachomatis accounts for 14–35% of cases (3)
  • other causative organisms include Neisseria gonorrhoeae (2–3% of cases)
  • however, based on the pattern of organisms isolated from the upper genital tract, the infection may often be polymicrobial (caused by more than one type of bacteria) (1)
    • this suggests that initial damage produced by C trachomatis or N gonorrhoeae may permit the opportunistic entry of other bacteria, including anaerobes
    • however, in many cases, no infection is found in the lower genital tract
      
      
• risk factors for developing PID include:
  • sexual behaviour related factors, for example (2):
    • women younger than aged 25 years
    • early age of first coitus
    • recent new partner (within the previous 3 months)
    • multiple sexual partners.
    • past history of STI in the woman or her partner
      
      
  • Iatrogenic - for example:
    • termination of pregnancy.
    • insertion of an intrauterine device - suggested that may be not immediate and within the past 4–6 weeks, especially in women with pre-existing gonorrhoea or C. trachomatis infection (2)
    • hysterosalpingography.
    • in vitro fertilization and intrauterine insemination
      
      
• in the UK, the prevalence of PID is about 2% among women between 16 and 46 years old
• 10% to 20% may become infertile, 40% will develop chronic pelvic pain, and 10% of those who conceive will have an ectopic pregnancy

Reference:

• 1. Savaris RF et al. Antibiotic therapy for pelvic inflammatory disease. Cochrane Database of Systematic Reviews 2020, Issue 8. Art. No.: CD010285. DOI:0.1002/14651858.CD010285.pub3.
• 2. Curry A et al. Pelvic Inflammatory Disease: Diagnosis, Management, and Prevention. Am Fam Physician. 2019 Sep 15;100(6):357-364.
• 3. Price MJ, Ades AE, Welton NJ, et al. Proportion of pelvic inflammatory disease cases caused by Chlamydia trachomatis: consistent picture from different methods. J Infect Dis. 2016 Aug 15;214(4):617-24.