Inducing factors and complication risks of pelvic inflammatory disease: a review

Pelvic inflammatory disease (PID) is a common infectious condition of the female upper genital tract that imposes a substantial global burden on women's reproductive health and overall quality of life. This narrative review aims to comprehensively synthesize current evidence on the inducing factors and complication risks of PID. We conducted a systematic literature search in PubMed, Embase, and Web of Science databases from January 2010 to December 2025, prioritizing high-quality evidence including systematic reviews, meta-analyses, large-scale population-based cohort studies, and national registry data. The review systematically categorizes PID etiologies into sexually transmitted infections, cervicovaginal dysbiosis, iatrogenic procedures (intrauterine device insertion, assisted reproductive technology, and intrauterine manipulations), anatomical abnormalities, underlying gynecological conditions, lifestyle habits, and environmental exposures, with a particular focus on the emerging role of cervicovaginal microbiota in idiopathic PID. Beyond well-established reproductive sequelae such as tubal infertility, ectopic pregnancy, and chronic pelvic pain, we also summarize evidence linking PID to a broad spectrum of under-recognized systemic complications, including ovarian and colorectal cancer, cardiovascular and metabolic disorders, intestinal obstruction, and mental health problems. The findings underscore the critical importance of early diagnosis, appropriate antimicrobial treatment, and comprehensive risk stratification for optimizing clinical outcomes and reducing the long-term burden of PID.