Chapter 167

Pelvic Inflammatory Disease

Sheila Ann Medina

Definition and Epidemiology

Pelvic inflammatory disease (PID) refers to a spectrum of inflammatory disorders of the upper genital tract in women. It can include any combination of endometritis, salpingitis, tubo-ovarian abscess (TOA), and pelvic peritonitis.¹ There is a wide variation in the signs and symptoms associated with PID; although acute signs and symptoms are often moderately severe, many women have subtle or mild symptoms that go unrecognized. Nonetheless, the long-term sequelae resulting from fallopian tube damage and scarring can be serious and include ectopic pregnancy, recurrent episodes of PID, chronic pelvic pain, and infertility.²^,³

It is estimated that each year in the United States, more than 750,000 women experience an episode of acute PID and 75,000 women are more likely to become infertile as a result of PID.⁴^–⁶ PID is the most common gynecologic reason for emergency department (ED) visits and hospitalizations in the United States. Women with PID make 2 million ED and office visits and incur health care costs exceeding $4 billion. PID affects more women of reproductive age, with a disproportionately higher incidence of African-American women.⁷ Although the number of PID-related ED visits and hospitalizations remains high, more than three fourths of women treated for PID in the United States are now treated as outpatients, a trend that has been increasing during the past two decades.² Based on research looking at trends in PID from 2001 to 2013, cases of PID (based on hospitalizations and estimated ambulatory cases) have decreased significantly, but the annual estimate of acute and unspecified PID cases diagnosed in the United States for 2009 and 2010 was greater than had previously been published.³ It is evident that PID remains an important public health concern for women and health care providers, especially those working in outpatient settings.

Direct costs for care of acute PID and its sequelae are estimated at $1.88 billion yearly, even though the majority of women receive care as outpatients.⁴ The high financial and social costs related to PID are important to consider if the full impact of this disease is to be appreciated.

Risk factors for PID include being younger than 25 years, having multiple sexual partners, not currently or consistently using contraception, and living in an area with a high prevalence of sexually transmitted diseases (STDs). There is a strong correlation between the incidence of STDs and PID in any given population. Other risk factors for PID include penetration of the cervical mucus barrier during medical procedures, including the insertion of an intrauterine contraceptive device, vaginal douching, and cigarette smoking.² A woman’s risk for PID is decreased if she uses barrier contraception, takes oral contraceptives, or has had a tubal sterilization.

The risk of PID in young women is significant; one in five cases of PID occur in women younger than 19, and one in eight adolescent girls will develop PID compared with one in 80 women older than 24 years.¹^,⁸ From 2001 to 2013, 46.8% of all U.S. high school students had engaged in sexual intercourse, and 15% had had four or more partners, making STDs a major public health problem for adolescents.⁹ Contact with multiple sexual partners, inconsistent use of contraception, and biologic vulnerability can account for the increased incidence of STDs in women younger than 25 years, although it does not fully account for the increased incidence of PID. Younger women with chlamydial infections of the cervix have a higher incidence of upper genital tract infection than do older women.¹⁰

Previous diagnosis of PID is a risk factor for subsequent episodes, with approximately 15% to 25% of all women with PID experiencing more than one episode.¹⁰ These subsequent infections are generally new, primary attacks of PID, not flares of latent or chronic infection. Reinfection is often related to contact with untreated sexual partners. In addition, one third of women with PID will develop chronic pelvic pain.⁸

Pathophysiology

PID is usually a polymicrobial infection caused by organisms that ascend from the vagina and cervix along the mucosa of the endometrium to infect the mucosa of the fallopian tubes. The most common organisms implicated in PID (one third to three quarters of cases) include Neisseria gonorrhoeae and Chlamydia trachomatis; however, microorganisms that can be part of the normal vaginal flora (e.g., anaerobes, Gardnerella vaginalis, Haemophilus influenzae, enteric gram-negative rods, and Streptococcus agalactiae) can also cause PID.¹^,² Newer data suggest that Mycoplasma genitalium may also play a role in PID and may be associated with milder symptoms.¹^,¹¹ Mycoplasma hominis and Ureaplasma urealyticum are also possible causative agents.¹ The mildest form of salpingitis involves tubal hyperemia, edema of the tubal wall, and exudate on the tubal surface and fimbriated ends.¹² If salpingitis is left untreated, further inflammatory changes of the pelvic organs occur, including tubal adhesions, pyosalpinx, and TOA.

The increased incidence of PID in young women may be explained by a larger cervical squamocolumnar junction, allowing easier colonization with N. gonorrhoeae or C. trachomatis, and by a decreased antibody response.¹⁰ However, PID is uncommon in pregnancy because of the physiologic changes in the uterus.¹¹ The uterotubal junction is closed as early as the seventh week of gestation, and the chorioamnion covers the endocervix around the 12th to 15th week. An ascending infection before the 12th week often leads to endometritis and spontaneous abortion. After the 12th week, it results primarily in chorioamnionitis.

Rarely, PID can result from secondary extension of infection of adjacent organs, as in appendicitis or diverticulitis. It may also result from hematogenous dissemination of tuberculosis or as a rare complication of a tropical disease such as schistosomiasis. The following discussion refers only to ascending infections resulting in PID.

Clinical Presentation

The clinical presentation of PID varies widely. Although some women are truly asymptomatic, others remain undiagnosed because of their mild or nonspecific signs and symptoms. These symptoms vary based on the pathogen responsible.¹³ These can include fever or chills, cramping, dysuria, low back pain, nausea and vomiting, abnormal vaginal bleeding (postcoital or intermenstrual bleeding), dyspareunia, and vaginal discharge. The most common presenting symptom is lower abdominal and pelvic pain of less than 2 weeks’ duration. The pain is typically described as dull and constant and is worsened by movement and sexual intercourse. The onset of symptoms occurs most commonly in the proliferative phase of the menstrual cycle. Complaints of fever or abnormal vaginal discharge may also be present.¹³

PID caused by gonococci is usually associated with a more intense inflammatory reaction in the tubal lumen than the reaction caused by chlamydial infection. Therefore the woman with a gonococcal PID may have a more acute presentation, often requiring hospitalization.¹⁴

Women with Fitz-Hugh–Curtis Syndrome (FHCS) are initially seen with right upper quadrant pain, pleuritic pain, and tenderness on liver palpation. These symptoms are often mistaken for hepatic disease, cholecystitis, or pneumonia.¹⁵

Physical Examination

The clinical diagnosis of acute PID is imprecise; lower abdominal pain may be mistakenly attributed to pregnancy (ectopic), ovarian cysts, or even appendicitis. No single history, physical, or laboratory finding is both sensitive and specific for the diagnosis of acute PID. According to the Centers for Disease Control and Prevention (CDC), empirical treatment of PID should be initiated in sexually active young women and other women at risk for STDs if they are experiencing pelvic or lower abdominal pain, if no cause of the illness other than PID (e.g., diverticulitis, ectopic pregnancy, or appendicitis) is identified, and if the pelvic examination is significant for one or more of the following criteria: cervical motion tenderness, uterine tenderness, or adnexal tenderness.¹ These criteria may not be sensitive enough to identify the more subtle cases of PID, and the following additional criteria enhance the specificity of the aforementioned minimum criteria and support a diagnosis of PID:

• Oral temperature above 38.3° C (101° F)

• Abnormal cervical or vaginal mucopurulent discharge

• Presence of white blood cells (WBCs) on saline microscopy of vaginal secretions

• Elevated erythrocyte sedimentation rate (ESR)

• Elevated C-reactive protein (CRP)

• Laboratory documentation of cervical infection with N. gonorrhoeae or C. trachomatis

Most women with PID have either mucopurulent cervical discharge or WBCs on microscopic evaluation of vaginal fluid. If the cervical discharge appears normal and no WBCs appear on the wet mount, the diagnosis of PID is unlikely and alternative causes of pain should be considered.¹

Diagnostics

Acute PID is difficult to diagnose because of the wide variation in signs and symptoms. The clinical diagnosis of symptomatic PID has a positive predictive value for salpingitis of 65% to 90% compared with laparoscopy.¹ A pregnancy test should be performed immediately to assess for the possibility of ectopic pregnancy, although a negative result is not conclusive. Pelvic ultrasound evaluation is indicated when TOA is suspected. Additional studies to consider include the rapid plasma reagin (RPR) test for syphilis and serologic studies for human immunodeficiency virus (HIV) infection. PID can be diagnosed clinically, and empirical therapy initiated on the basis of some of the aforementioned findings. However, an evaluation that includes more extensive studies may be necessary if the diagnosis is unclear.

The most specific criteria for diagnosis of PID include endometrial biopsy with histopathologic evidence indicative of endometriosis; transvaginal ultrasonography, magnetic resonance imaging (MRI), or Doppler studies suggesting pelvic infection; and laparoscopic abnormalities consistent with PID.¹⁶ However, these extensive procedures may not be warranted in all cases. Thus, an accurate diagnosis of PID is difficult, given the wide variation in symptoms on presentation. However, the potential damage to the reproductive health of women with even mild or atypical PID is well documented.¹ Diagnosis and management of other causes of lower abdominal pain are unlikely to be affected by the initiation of empirical therapy for PID.

Diagnostics

Pelvic Inflammatory Disease

Laboratory