Overview of PID
Pelvic inflammatory disease (PID) is severe inflammation that results when vaginal and cervical infections spread into the uterus, fallopian tubes, ovaries, and surrounding tissues. PID can cause serious damage to a woman's reproductive tract, causing infertility, chronic pain, and tubal pregnancy. PID can be acute (short, sudden flare-up) or chronic (persistent inflammation and infection).
Because PID primarily involves the fallopian tubes, health care practitioners sometimes use the term "salpingitis" when referring to PID. Salpingitis is inflammation of the fallopian tubes. The terms "endometritis" and "oophoritis" are also sometimes used. Endometritis is inflammation of the uterus, and oophoritis is inflammation of the ovaries.
PID is one of the most common and serious complications of sexually transmitted diseases (STDs) in women. Up to 40 percent of untreated lower genital tract infections progress to PID. Chlamydia and gonorrhea are the two most common causes. PID usually develops from 2 days to 3 weeks after exposure to the bacteria, but it may take months to develop.
Prompt diagnosis and treatment can prevent the development of irreversible, long-term complications. Routine STD testing for sexually active women is an important preventive measure, because as many as 50 percent of PID cases are "silent," that is, without symptoms. Asymptomatic PID can cause permanent damage.
Incidence and Prevalence of PID
In a 1995 U.S. study, 8 percent of all women and 11 percent of African American women reported being treated for PID during their reproductive years. These numbers are down from 11 and 17 percent, respectively, in 1988. Still, PID remains a significant women's health problem. In the United States, more than 1 million women are treated for PID every year, and 200,000 to 300,000 of them require hospitalization. The situation is even worse in developing countries where health care is not readily accessible.
Causes of PID
When disease-causing bacteria migrate through the vagina and cervix, they invade and damage the tissues of the upper genital tract, leading to inflammation and tissue damage. The fallopian tubes, uterus, and/or ovaries may become inflamed, potentially causing obstruction, permanent scarring, and chronic pain.
The two most common culprits are the bacterium that causes gonorrhea (Neisseria gonorrhea) and the bacterium responsible for vaginal chlamydial infections (Chlamydia trachomatis).
PID caused by chlamydia is typically "silent," that is, asymptomatic and of which the woman is unaware. It can cause permanent damage and often does because there are no warning signs. Most infertility from PID is caused by chlamydia.
Other bacteria can also cause PID. For example, Gardnerella vaginalis, the bacteria that can cause vaginitis, but is also often found in healthy, asymptomatic women, has been implicated in some cases. Bacteroides spp., a common bacteria of the colon, may also play a causal role.
How bacteria access the upper reproductive tract
During most of a woman's menstrual cycle, the cervical mucus at the opening of the cervix is thick and acts like a plug, keeping sperm and bacteria from entering the uterus. The plug dissipates during ovulation (when rising levels of estrogen make the mucus clear, thin, and watery) and menstruation, making it easier for bacteria to enter the uterus and upper reproductive tract.
Also during menstruation, many women experience backward menstrual flow, or retrograde menstruation. The backward flow can carry microorganisms as it moves back from the uterus to the fallopian tubes. It is not clear why, but bacterial infections that cause menses-associated PID are usually gonorrheal, not chlamydial.