DEFINITION AND EPIDEMIOLOGY
Pelvic inflammatory disease (PID) is a complex inflammatory disorder of the female upper genital tract that usually develops as a result of an initiating sexually transmitted infection, but can also be caused by iatrogenic uterine instrumentation.1–6 The term denotes a wide spectrum of histopathologic entities including endometritis, salpingitis, oophoritis, peritonitis, and abscess formation.
Pelvic inflammatory disease can manifest in a wide range of symptoms, from subtle pelvic discomfort to peritonitis and hemodynamic shock. A distinct entity called subclinical PID has been recognized as an asymptomatic infection with evidence of upper genital tract inflammation. Despite lack of symptoms, subclinical PID is suspected to result in the same long-term reproductive sequelae as its symptomatic counterpart.7–10
According to the 2013/4 National Health and Nutrition Examination Survey, which queried women aged 18–44 years, the lifetime prevalence of PID is estimated to be 4.4% in sexually experienced women.11 Estimates of the true burden of this disease, however, are likely inaccurate because this syndrome is not reportable and is often underdiagnosed because of atypical presentations. Incidence of symptomatic PID is decreasing, from a peak of 1 million cases annually in the early 1980s to 176,000 in 2005 to 51,000 in 2015.12 Total medical cost of PID was estimated at $1.5 billion for the year 2006.13
Demographic, behavioral, and contraceptive practices have been evaluated in cross-sectional studies as risk factors for PID. Previously, risk factors such as age younger than 19 years,14–16 lower socioeconomic group,14,17 nonwhite race,14,15,18 lack of married status,14,19 and lower education15,20 were reported to be associated with increased risk of PID. However, the 2013/4 NHANES survey found that those with highest risk include women with sexual debut less than 12 years of age, with 10 or more lifetime male vaginal sexual partners, or previously diagnosed STI. Of note, there was no significant difference in prevalence based on age, race/ethnicity, income, or health insurance coverage. However, in those women with no history of STIs, lifetime prevalence of PID in black women was 2.2 times that of white women. This may indicate that STIs are being underdiagnosed in black women.11 A history of PID may be an independent risk factor for recurrence.15–17 Use of substances such as alcohol,16,22 tobacco,15,17,20,23 and cocaine15 may also increase PID risk. Additionally, engaging in sex during menses17,24 and douching25–27 are behaviors that remain controversially associated with PID, as studies have been conflicting. Multiple retrospective studies have found an association between douching and PID; however, a prospective study in 2006 demonstrated no association between douching and PID.17
Contraceptive practices also alter the risk of PID. Lack of any contraception is ...