• • No set of signs or symptoms is pathognomonic for pelvic inflammatory disease (PID), and most laboratory tests are nonspecific for its diagnosis.
  
• • Because clinically mild and subclinical PID causes most cases of postinfectious tubal factor infertility, ectopic pregnancy, and chronic pelvic pain due to pelvic scarring in women, a low threshold should be used to make the diagnosis of PID.
  
• • All sexually active young women and other women at risk for sexually transmitted diseases (STDs) who complain of acute lower abdominal or pelvic pain; demonstrate uterine, adnexal, or cervical motion tenderness on examination; and have no other causes for these symptoms, should be diagnosed and treated for PID.

PID is the most common serious infection acquired by sexually active women in the United States. Between 750,000 and one million women develop PID annually, with a 1.5% annual incidence among adolescents and higher rates among nonwhite populations. Since the early 1990s, the numbers of hospitalizations and initial visits to outpatient facilities including physicians’ offices for PID has steadily declined. Nevertheless, PID led to 123,000 initial visits to physicians’ offices in 2003, a figure that underestimates the true number of new outpatient PID cases in the United States because the nature of physician office reporting is inherently incomplete, and excludes emergency department visits.

Postinfectious tubal factor infertility is the second most common cause of female infertility in the United States. Yet the majority of women with this condition do not have a clear history of PID, suggesting that many cases of PID are subclinical and therefore go untreated. Several studies have shown that upon in-depth questioning, 70–80% of patients with tubal factor infertility have a history of lower abdominal pain. Demographic and microbiologic factors associated with acute and subclinical PID are similar, supporting the hypothesis that they share the same pathophysiologic mechanisms. Therefore, until improved tests are available to diagnose subclinical disease, clinicians should use a low threshold in making the diagnosis of PID, and women at risk of an STD should be educated to recognize the symptoms of PID and to seek immediate care and treatment.

Neisseria gonorrhoeae and Chlamydia trachomatis are common causes of PID. In a recent US multicenter study of women with mild to moderate PID, these pathogens accounted for 20% and 21% of cases, respectively; coinfection with N gonorrhoeae and C trachomatis was found in 6% of cases. These bacteria initially cause an endocervical infection; however, as a result of poorly defined anatomic, pathologic, and immunologic changes, between 10% and 20% of primary endocervical gonococcal and chlamydial infections will lead to an ascending infection of the endometrium and fallopian tubes. Over the past two decades, the proportion PID cases caused by N gonorrhoeae and C trachomatis has declined in parallel with the overall reduction of these STDs in the US population.

In many studies, neither gonorrhea nor chlamydia is detected in 60% or more of women with PID. Anaerobic and facultative bacteria have frequently been isolated from the tube, cul-de-sac, and endometrium of women with PID. The highest prevalence of such organisms was seen in studies using culdocentesis, raising the question of transvaginal contamination. Lower prevalences of anaerobic bacteria have generally been discovered in laparoscopically collected specimens. Many of the anaerobic bacteria isolated from the upper genital tract are also commonly found in low concentrations in normal vaginal flora, and at far greater concentrations among women with bacterial vaginosis. In fact, the presence of bacterial vaginosis has been associated with a twofold or greater increased risk of PID.

Prevotella bivius, Bacteroides species, Peptostreptococcus species, staphylococci, group B–D streptococci, Gardnerella vaginalis, Escherichia coli, and more recently, using molecular techniques, novel bacteria including Leptotrichia species and Atopobium vaginae have been isolated from the upper genital tract of women with salpingitis and pelvic abscesses. These organisms have also been isolated from women with gonococcal and chlamydial PID, supporting the hypothesis that N gonorrhoeae and C trachomatis may cause primary infection of the upper genital tract that is followed by secondary infection of the endometrium and fallopian tubes by vaginal organisms such as those associated with bacterial vaginosis. However, anaerobic bacteria are isolated less commonly in women with milder disease. Because of the data just cited, some anaerobic coverage is included in all the inpatient and most outpatient antibiotic regimens recommended for the treatment of PID by the Centers for Disease Control and Prevention (CDC; see Tables 8–3 and 8–4).

Primary measures to identify and treat asymptomatic genital tract infections such as C trachomatis have decreased the frequency of PID. Although condom use is associated with a decreased risk of PID, increased numbers of recent sex partners and history of a prior STD are associated with an increased risk. Therefore, women at risk of an STD, specifically adolescents, HIV-infected women, and women who report high-risk sexual behaviors, should be counseled on the need to reduce their sexual exposure. Hormonal contraception, including combined oral contraceptives and depomedroxyprogesterone, do not appear to affect the risk of PID. Although controversy remains, most experts agree that currently marketed intrauterine devices (IUDs) do not increase risk of PID except at the time of insertion; however, women require screening for N gonorrhoeae and C trachomatis prior to IUD insertion.