The term pelvic inflammatory disease (PID) usually refers to an ascending infection of the endometrium, (the membrane that lines the uterus) and/or fallopian tubes, (the tube that connects the ovary to the uterus). These infections are sometimes considered primary meaning that they occur spontaneously, usually sexually transmitted, or secondary meaning that they come as a result of something else such as surgery, insertion of an intrauterine device, or termination of pregnancy.(1) Worldwide, PID is a leading cause of infertility, and in the United States, it is considered responsible for the recent upswing in ectopic pregnancy.(2)

Pelvic inflammatory disease is almost exclusively a disease of sexually active women and may be of the chronic or acute type. Chronic PID caused by Mycobacterium tuberculosis has become uncommon in industrialized countries, however, PID caused by Chlamydia trachomatis is thought to be common. In general, first episodes of acute PID are likely to be caused by sexually transmitted pathogens. These pathogens are less often the cause in women with intrauterine devices, and/or invasive diagnostic or therapeutic procedures. Infections due to use of IUD or diagnostic procedures tend to be caused by ascending infection from the vaginal area.

The term, pelvic inflammatory disease has been used to describe an entire group of infections including simple cervicitis, to endometritis, to salpingitis, (inflammation of the fallopian tubes), to pelvic peritonitis, and finally to generalized peritonitis, perihepatitis, or pelvic abscess. The distinctions may be important, however, since confirmed cases of salpingitis, or inflammation of the fallopian tubes, is most frequently associated with long-term disease states. These disease states include infertility, ectopic pregnancy due to tubal damage, chronic pelvic pain, and sometimes recurrent PID. Sometimes the inflammation of the fallopian tubes (salpingitis) results in infertility in up to 13 percent of women following a single episode of PID, and in up to 75 percent of women after three or more episodes of PID.(3) The risk of ectopic pregnancy is increased approximately eight fold after one or more episodes of PID.(4)

Approximately 85 percent of all cases of acute PID occur by sexual transmission in females of reproductive age, with another 15 percent following procedures requiring the use of some type of instrument such as those used in IUD insertion, abortion, or dilation and curettage.(4, 5) Acute PID develops in 1 percent of sexually active young women annually and causes more morbidity in women (15 to 25 years of age) than all other serious infections combined.(4, 6)

There are several factors that seem to be implicated in the upward spread of infection in PID. Some of these include: attachment to sperm that migrate upwards into the tubes; use of an IUD; vaginal douching; menstruation; and the presence of thin cervical mucous which cannot provide the needed protection. It is important that a person be diagnosed and receive treatment early on in the disease in order to prevent the damage to the fallopian tubes. It is difficult for a physician to determine the damage to the fallopian tubes because there are really no diagnostic tests that can be used. Currently, only the use of a device called a laparoscope allows the clinician to determine damage and it is not practical to use this procedure on a regular basis.