Can Trichomoniasis Lead to Pelvic Inflammatory Disease?
The evidence suggests trichomoniasis has a modest association with PID and endometritis, though the relationship is less established than with chlamydia or gonorrhea, and current CDC guidelines do not list T. vaginalis as a primary causative organism of PID.
Primary Causative Organisms of PID
The established microbial etiology of PID centers on specific pathogens:
C. trachomatis and N. gonorrhoeae are the primary sexually transmitted organisms causing PID, with 10-40% of untreated cervical infections progressing to symptomatic upper genital tract disease 1, 2.
Anaerobic and aerobic bacteria (Bacteroides, Peptostreptococcus, G. vaginalis, Streptococcus species) are isolated from the upper genital tract in 25-50% of acute PID cases, often in polymicrobial infections 1.
Bacterial vaginosis serves as an antecedent to polymicrobial PID, with BV-associated organisms contributing to upper tract infection 1, 2.
Trichomoniasis and PID: The Evidence
The relationship between T. vaginalis and PID is less clearly defined:
CDC guidelines from 1991,2002, and 2006 do not list T. vaginalis among the recognized etiologic agents of PID 1. The guidelines specifically mention C. trachomatis, N. gonorrhoeae, anaerobes, and aerobic bacteria, but trichomoniasis is discussed separately under vaginal discharge syndromes 1.
Cervicitis can accompany trichomoniasis, and cervicitis may be a sign of upper genital tract infection, though this does not establish direct causation 1.
Recent research suggests a possible association: In the PEACH study, women with trichomoniasis had twice the odds of baseline endometritis (AOR: 1.9,95% CI 1.0-3.3) and higher rates of persistent endometritis at 30 days (AOR: 2.6,95% CI 0.7-10.1), though the latter was non-significant 3.
Multiple studies have implicated T. vaginalis as a contributor to cervicitis, urethritis, and potentially atypical PID, though the evidence remains less robust than for chlamydia and gonorrhea 4, 5, 6.
Clinical Implications
The practical approach should focus on established PID pathogens while recognizing trichomoniasis as a potential contributor:
Screen and treat for C. trachomatis and N. gonorrhoeae as the priority in preventing PID, as these have the strongest evidence base 1, 2.
Evaluate women with cervicitis for trichomoniasis using sensitive testing methods (not just wet mount, which has only 50% sensitivity), and treat if present 1, 4.
In women with PID, test for trichomoniasis alongside standard STI testing, as it may contribute to the polymicrobial nature of upper tract infection 3, 7.
Treat trichomoniasis with metronidazole 2g single dose or 500mg twice daily for 7 days, ensuring partner treatment to prevent reinfection 8, 1.
Important Caveats
The association between trichomoniasis and PID sequelae (infertility, recurrent PID) remains uncertain, with modest but non-significant findings in prospective studies 3.
Wet mount microscopy underestimates true T. vaginalis prevalence, so nucleic acid amplification testing should be used when available for accurate diagnosis 4, 5.
Trichomoniasis increases HIV transmission risk and causes adverse pregnancy outcomes, making treatment important even if the PID link is not definitively established 8, 4, 6.