Each year in the United States, more than 1 million women experience an episode of acute PID, with the rate of infection highest among teenagers. More than 100,000 women become infertile (cannot become pregnant) each year as a result of PID, and a large proportion of the 70,000 ectopic (tubal) pregnancies occurring every year are due to the consequences of PID. In 1990 alone, an estimated four billion dollars were spent on PID and its complications.

Cause

PID occurs when disease-causing organisms migrate upwards from the vagina and cervix into the upper genital tract. Many different organisms can cause PID, but most cases are associated with gonorrhea and chlamydial infections, two very common STDs. Scientists have found that bacteria normally present in the vagina and cervix may also play a role.

Investigators are learning more about how these organisms cause PID. The gonococcus probably travels to the fallopian tubes, where it causes sloughing of some cells and invades others. It is believed to multiply within and beneath these cells. The infection then may spread to other organs, resulting in more inflammation and scarring. Chlamydia and other bacteria may behave in a similar manner. It is not known how other bacteria that normally inhabit the vagina (e.g., organisms such as Gardnerella vaginalis and Bacteroides) gain entrance into the upper genital tract. It appears that the cervical mucus plug and secretions, believed to prevent the spread of microorganisms to the upper genital tract, are less effective during ovulation and menstruation. In addition, the organisms may gain access more easily during menstruation, if menstrual blood flows backward from the uterus into the fallopian tubes, carrying the organisms with it. This may explain why symptoms of PID caused by gonorrhea or chlamydia more often begin immediately after menstruation rather than at any other time during the menstrual cycle.

Symptoms

The major symptoms of PID are lower abdominal pain and abnormal vaginal discharge. Other symptoms such as fever, pain in the right upper abdomen, painful intercourse, and irregular menstrual bleeding can occur as well. PID, particularly when caused by chlamydia, may produce only minor symptoms or no symptoms at all, even though it can seriously damage the reproductive organs.

Risk Factors for PID

• Women with sexually transmitted diseases--especially gonorrhea and chlamydia--are at greater risk of developing PID; a prior episode of PID increases the risk of another episode because the body's defenses are often damaged during the initial bout of upper tract infection.

• Sexually active teenagers are more likely to develop PID than are older women.

• The more sexual partners a woman has, the greater her risk of developing PID.

• IUD insertion, induced abortion, and other procedures during which instruments are passed through the cervix into the uterus increase the risk of PID.

Diagnosis

PID can be difficult to diagnose. If symptoms such as lower abdominal pain are present, the doctor will perform a physical exam to determine the nature and location of the pain. Additional evaluation should be conducted to determine if the patient has a fever, abnormal vaginal or cervical discharge, and evidence of cervical infection with gonorrhea or chlamydia. If the findings of this exam suggest that PID is likely, current guidelines advise doctors to begin treatment.

If more information is necessary, the doctor may order other tests, such as a sonogram, endometrial biopsy, or laparoscopy to distinguish between PID and other serious problems that may mimic PID. Laparoscopy is a surgical procedure in which a tiny, flexible tube with a lighted end is inserted through a small incision just below the navel. This procedure allows the doctor to view the internal abdominal and pelvic organs as well as take specimens for cultures or pathologic studies, if necessary.

Treatment

Because culture specimens from the upper genital tract are difficult to obtain and because multiple organisms are usually responsible for an episode of PID, at least two antibiotics are given so that they will be effective against a wide range of infectious agents. The infection may still be present after the symptoms are gone, so it is important to finish taking all of the medicine, even if symptoms go away. Patients should be re-evaluated by their physician 2 to 3 days after treatment is begun to be sure the antibiotics are working to cure the infection.

About one-fourth of women with suspected PID must be hospitalized. This may be recommended if the patient is severely ill, if she cannot take oral medication and needs intravenous antibiotics, if she is pregnant or is an adolescent, or if the diagnosis is uncertain and may include an abdominal emergency such as appendicitis.

Many women with PID have sex partners who have no symptoms. Because of the risk of reinfection, however, sex partners should be treated. Even if they do not have symptoms, they may be infected with organisms that can cause PID.

Consequences of PID

Women with recurrent episodes of PID are more likely than women with a single episode to suffer long-term consequences, such as infertility, tubal pregnancy, or chronic pelvic pain. Infertility occurs in approximately 20 percent of women who have had PID.

However, most women with tubal infertility never have had symptoms of PID. Organisms such as chlamydia can silently invade the fallopian tubes and result in scarring, which blocks the normal passage of eggs into the uterus.

A woman who has had PID has a six- to tenfold increased risk of tubal pregnancy, in which the egg can become fertilized but cannot pass into the uterus to grow. Instead, the egg usually attaches in the fallopian tube that connects the ovary to the uterus. The fertilized egg cannot grow normally in the fallopian tube. This type of pregnancy is life-threatening to the mother, and almost always fatal to her fetus. It is the leading cause of maternal death in African- American women.

In addition, untreated PID results in chronic pelvic pain and scarring in about 20 percent of patients. These conditions are difficult to treat but are sometimes improved with surgery.

Another complication of PID is the risk of repeat episodes. As many as one-third of women who have had PID will have the disease at least one more time. With each episode of reinfection, the risk of infertility is increased.

Prevention

You can play an active role in protecting yourself from PID by taking the following steps:

• If you think you have a sexually transmitted disease, get tested. Early treatment may prevent the development of PID.

• To prevent sexually transmitted diseases that can cause PID, use a barrier contraceptive such as a diaphragm and ask your partner to use a latex condom (rubber).

Although much has been learned about the biology of the microbes that cause PID and the ways in which they damage the body, there is still much to learn. Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID) are studying the effects of antibiotics, hormones, and substances that boost the immune system on the interactions between STD organisms and fallopian tube tissue. These studies may lead to insights about how to prevent infertility or other complications of PID. Vaccines to prevent gonorrhea and chlamydial infection are also under development.

Meanwhile, the search continues for faster and more accurate ways to detect PID, particularly in women with "silent" or asymptomatic PID.

Prepared by:
Office of Communications
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Bethesda, MD 20892

Public Health Service
U.S. Department of Health and Human Services