What Is Pelvic Inflammatory Disease?

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Pelvic inflammatory disease (PID) is inflammation of the female reproductive organs and the surrounding area. This means that PID features inflammation of the cervix (cervicitis), the fallopian tubes (salpingitis), the lining of the uterus (endometritis), and the membrane that lines the pelvic and abdominal cavities (peritonitis). Typically, the inflammation is due to a bacterial infection, usually with the species Chlamydia trachomatis or Neisseria gonorrhoeae, which are sexually transmitted infections (STIs). But you also can develop PID from non-sexual infections of bacteria coming either from outside, or from your body. Such non-sexual infections can result from foreign objects in your reproductive tract, such as a douche or tampon (especially if left in too long) or occasionally from an intrauterine device (IUD) inserted for birth control. It is unusual for women to develop PID during pregnancy, but when it does happen during pregnancy, usually it is during the first trimester.

More commonly, PID is an issue affecting how easily you can become pregnant in the first place and your chances of developing an ectopic pregnancy (a pregnancy outside of the uterine cavity), especially an ectopic pregnancy located in the fallopian tube. Thus, PID is a major health issue in young women with implications on fertility and on the risk for ectopic pregnancy.

Based on data from the year 2018, the US Centers for Disease Control and Prevention reports approximately 2.5 million women, ages 18–44, in the United States have been diagnosed with PID at some point in life. You are at elevated risk for PID if you have multiple sex partners, if your partner has multiple sex partners, if you are below age 25, if your age at your first intercourse was below 15 years, if you have a history of sexually-transmitted disease (STD), or, if your ethnicity is not Caucasian. Also, if you have recently received certain types of IUD, this may possibly put you at risk.

Unless known to be pregnant already, any premenopausal woman who is suffering from abdominal pain must be given a pregnancy test, in which your urine is tested for the presence of the hormone beta- human chorionic gonadotropin (β-hCG). This may be followed up with a β-hCG blood test. A positive pregnancy test will lead to testing with a goal of finding, or ruling out, an ectopic pregnancy. If the pregnancy test is negative, then appendicitis and PID will be high on the list of possibilities, especially if you are young (below age 25), and have other risk factors. On the other hand, doctors will be thinking more about gallbladder problems, if you are at least in your forties, and particularly if you have given birth to many babies. Doctors will also test your blood for signs of infection and inflammation, and possibly for STIs. You will also get a pelvic ultrasound exam, and a procedure called laparoscopy in which the gynecologist can view the inside of your pelvis and abdomen with a camera and light through a tube to look for inflammation.

PID causes severe abdominal pain and often fever, plus vaginal discharge and bleeding, painful urination, and pain (and sometimes bleeding) with intercourse. As noted above, PID is rare during pregnancy. When it does occur during pregnancy, usually it is during the first trimester. When this happens, PID can be easily confused with other emergencies that cause pain, such as appendicitis, and any diagnostic confusion related to pain and infection during pregnancy can be dangerous.

PID is often an issue related to fertility and ectopic pregnancy, because of scarring in the fallopian tubes. Normally, after leaving the ovary, an ovum (egg) moves through the fallopian tube, where it can be fertilized by a sperm cell, producing a zygote. The zygote continues through the tube as it develops into a blastocyst, which implants in the endometrium, the lining of the uterus. Fallopian tube scarring from PID makes it difficult to get through the tube. As a result, fertilized ova will typically die, rather than reaching the endometrium and implanting, and so PID impairs fertility. Alternatively, sometimes a blastocyst will get stuck in the tube and take root there, causing a tubal pregnancy. Such a pregnancy is not viable, at least with the current level of medical technology. If it does not terminate itself very early, the growth of the embryo in the tube will cause severe abdominal pain and eventually the tube can rupture, causing internal bleeding, which can lead to shock, a potentially fatal condition.

Whether it occurs during pregnancy (rare), or outside of pregnancy, PID must be treated with antibiotic medication. The first choice antibiotic is ceftriaxone, which is injected and not thought to be dangerous during pregnancy. Outside of pregnancy, the next choice is doxycycline, which is best avoided during pregnancy, but there are still choices of regimens that are not thought to be harmful in pregnancy. Fever should be treated with anti-fever medication such as acetaminophen. If PID occurs during pregnancy, if it is not discovered early and treated with appropriate antibiotics, there is a risk that the fetus will be lost later in the pregnancy. PID is quite rare during the year after a woman has given birth, but if PID does develop while you are nursing, you need antibiotic treatment. Generally, the antibiotics that are given for PID are considered compatible with nursing, when given for short periods of time.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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