The Dangers of PID: A Silent Infection That Affects Millions of Women

Pelvic inflammatory disease, or PID, is an infection of the upper female reproductive system, including the uterus, fallopian tubes, and ovaries. It can cause a number of serious complications, including infertility. The female reproductive system includes all of internal and external organs that help with reproduction. The internal sex organs are the ovaries, which are the female gonads, the fallopian tubes, two muscular tubes that connect the ovaries to the uterus, and the uterus, which is the strong muscular sack that a fetus can develop in. The neck of the uterus is called the cervix, and it protrudes into the vagina.

At the opening of the vagina are the external sex organs, and these are usually just called the genitals and they’re in the vulva region. They include the labia, the clitoris, and the mons pubis. The vagina, uterus, and fallopian tubes all have a mucosa, which is a layer of epithelial cells that lines the inside of these organs. PID usually develops from a bacterial infection in the vagina or cervix which causes inflammation of this mucosal layer. About 60 percent of the time, this changes the composition of the bacterial flora in the vagina, also called bacterial vaginosis.

Because the reproductive tract is essentially one long tunnel that starts at the ovaries and ends at the external sex organs, the infection can travel up the tract pretty easily. Some mechanisms can make it even easier! For example, the cervical mucus, which normally acts as a barrier preventing bacteria from entering the uterus, may become less effective. The mucus can become thinner as a result of normal variations throughout the menstrual cycle, or alternatively, it can become less effective in the context of bacterial vaginosis, which is when the normal balance of the vaginal flora is altered, and anaerobic bacteria proliferate and degrade the cervical mucus.

Other factors contributing to an infection may be retrograde menstruation, which is when menstrual blood flows back through the fallopian tubes and into the pelvic cavity instead of out of the body, and also sexual intercourse. Now, PID is most problematic when the infection reaches the fallopian tubes, in which case it’s called salpingitis. If it also affects the ovaries, it’s called salpingo-oophoritis. The infection triggers a response from the body, which sends in neutrophils, plasma cells, and lymphocytes into the fallopian tubes. That sounds like a good thing, right?

But this actually damages the tubal epithelium and the tubes become filled with pus. When scar tissue forms to repair the damage, areas with damaged epithelium tend to stick to one another, creating closed-off pockets and little dead-end pouches in the fallopian tubes. This scarring in the fallopian tubes can lead to a number of complications related to PID. If pus builds up in the tube and ovary, it can turn into a tubo-ovarian abscess, which can be life-threatening if it ruptures. If a watery fluid builds up in a pocket created by scar tissue in the tubes, this is called hydrosalpinx and it can cause the affected area to become swollen.

In general, because of the structural damage it causes in the fallopian tubes, individuals who have had PID tend to have more difficulty getting pregnant, and have a higher risk for ectopic pregnancy and chronic pelvic pain. One last complication is Fitz-Hugh-Curtis syndrome, which occurs when the inflammation from PID spreads to the peritoneum, and, from there, to Glisson's capsule, which surrounds the liver. This results in “violin string” adhesions, or thin strings of scar tissue that attach the liver to the peritoneum.

There are many different bacteria that are associated with PID, but the most common are Neisseria gonorrhoeae and Chlamydia trachomatis, which are responsible for the sexually transmitted infections gonorrhea and chlamydia, respectively. Occasionally, PID can be caused by other forms of bacteria introduced in the reproductive tract by surgery, abortion, or even normal vaginal childbirth. Most of the time the infection is caused only by one type of bacteria but in about 30-40% of cases it becomes polymicrobial. Essentially, the original infection makes it easier for other bacteria to settle into the reproductive tract. Because of the relationship with chlamydia and gonorrhea infections, sexually active females, particularly those who have multiple sexual partners and do not use condoms, are most at risk of developing PID.

Some women will have few or no symptoms of PID. When there are noticeable symptoms, they include pelvic pain, tenderness around the ovaries and fallopian tubes, fever, and abnormal vaginal discharge. Diagnosis of PID is usually based on clinical findings - particularly pelvic pain and cervical motion tenderness, which is when mobilizing the cervix during a vaginal exam causes pain or discomfort. Tenderness in the right upper quadrant of the abdomen is also common if Fitz-Hugh-Curtis syndrome has developed. There’s no specific test for PID, but there are some that can support the diagnosis, like testing vaginal discharge for signs of bacterial vaginosis, doing a nucleic acid amplification test to look for chlamydia and gonorrhea DNA in a sample taken from the inside of the vagina or cervix, or doing a laparoscopy of the fallopian tubes.

An ultrasound can show if there is fluid in the fallopian tubes, and whether a tubo-ovarian abscess or hydrosalpinx is present. Treatment involves giving a mix of antibiotics, usually an injection of ceftriaxone or cefotetan followed by 14 days of oral doxycycline and metronidazole, to treat the bacterial infection responsible for PID. Acetaminophen can be given to manage the pain until the antibiotics have treated the infection. Occasionally, surgery will be done to remove adhesions that are causing pain or to treat complications of PID, such as tubo-ovarian abscesses and hydrosalpinx.

All right, as a quick recap… Pelvic inflammatory disease is an infection of the upper female reproductive system. It caused inflammation of the mucous membrane of the inner reproductive tract, which damages the epithelium and results in scarring and adhesions, particularly in the fallopian tubes. It is usually caused by Neisseria gonorrhoeae and Chlamydia trachomatis, which are the bacteria responsible for chlamydia and gonorrhea. Complications include infertility, ectopic pregnancies, and tubo-ovarian abscesses.