Aside from AIDS, the most common and serious complication of sexually transmitted diseases (STDs) among women is pelvic inflammatory disease (PID), an infection of the upper genital tract. PID can affect the uterus, ovaries, fallopian tubes, or other related structures. Untreated, PID causes scarring and can lead to infertility, tubal pregnancy, chronic pelvic pain, and other serious consequences.

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 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 1997 alone, an estimated $7 billion was spent on PID and its complications.

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

Investigators are learning more about how these organisms cause PID. The gonococcus, Neisseria gonorrhea, probably travels to the fallopian tubes, where it causes sloughing (casting out) of some cells and invades others. Researchers think it multiplies within and beneath these cells. The infection then may spread to other organs, resulting in more inflammation and scarring.

Chlamydia trachomatis and other bacteria may behave in a similar manner. Researchers do not know how other bacteria that normally inhabit the vagina (e.g., organisms such as Gardnerella vaginalis and Bacteroides) gain entrance into the upper genital tract. The cervical mucus plug and secretions may help prevent the spread of microorganisms to the upper genital tract, but it may be less effective during ovulation and menses. In addition, the gonococcus may gain access more easily during menses, 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 often begin immediately after menstruation as opposed to any other time during the menstrual cycle. It is noteworthy that the co-incidence of menses and chlamydial infection is not a prominent feature of chlamydial PID.

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 chlamydial infection, may produce only minor symptoms or no symptoms at all, even though it can seriously damage the reproductive organs.

Women with STDs - especially gonorrhea and chlamydial infection - 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 genital 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.

Recent data indicate that women who douche once or twice a month may be more likely to have PID than those who douche less than once a month. Douching may push bacteria into the upper genital tract. Douching also may ease discharge caused by an infection, so the woman delays seeking health care.

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. The doctor also should check the patient for fever, abnormal vaginal or cervical discharge, and evidence of cervical chlamydial infection or gonorrhea. 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 microscopic studies, if necessary.

Because culture of specimens from the upper genital tract are difficult to obtain and because multiple organisms may be responsible for an episode of PID, especially if it is not the first one, the doctor will prescribe at least two antibiotics that are effective against a wide range of infectious agents. The symptoms may go away before the infection is cured. Even if symptoms do go away, patients should finish taking all of the medicine. Patients should be re-evaluated by their physicians two to three 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. The doctor may recommend this if the patient is severely ill; if she cannot take oral medication and needs intravenous antibiotics; if she is pregnant or is an adolescent; if the diagnosis is uncertain and may include an abdominal emergency such as appendicitis; or if she is infected with HIV (human immunodeficiency virus, the virus that causes AIDS).

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

Women with recurrent episodes of PID are more likely than women with a single episode to suffer scarring of the tubes that leads to infertility, tubal pregnancy, or chronic pelvic pain. Infertility occurs in approximately 20 percent of women who have had PID.

Most women with tubal infertility, however, never have had symptoms of PID. Organisms such as C. trachomatis can silently invade the fallopian tubes and cause scarring, which blocks the normal passage of eggs into the uterus.

A women 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, which 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 pregnancy-related death in African-American women.

In addition, untreated PID can cause 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 repeated attacks of PID. 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.