PID refers to the acute clinical syndrome attributed to the ascending spread of infection in women from the vagina and endocervix to the endometrium (lining of the uterus), fallopian tubes, and/or adjoining structures.
The ascent of infection has three stages:
Symptoms are not always present, and because PID is common among sexually active women, it is often known as the "silent epidemic".
As already mentioned, PID can be caused by Chlamydia trachomatis and Neisseria gonorrhoeae, and also by other infectious agents.
Chlamydia is responsible for 50% of PID cases, and gonorrhoea is the cause in 25% of cases. The risk of salpingitis in young women with lower genital tract chlamydial infection is one in 12, and one in 10 for gonorrhoea.
Non-gonococcal urethritis is the most common STD among Australian men. Chlamydia has been found to be the agent in up to 70% of men with non-gonococcal urethritis, and in up to 80% of men with a related syndrome, post-gonococcal urethritis.
It has been estimated that each year in Australia 10,000 women are treated for PID as in-patients in hospitals, but as many as 10 to 30 times that number may be treated as outpatients or suffer more subtle forms of infection. It has also been estimated that chlamydia, the major cause of PID, costs between $75 million and $150 million a year in Australia.
There have been no Australian studies to estimate actual prevalence, however it is known that in the USA PID affects an estimated 4 million women each year, with a yearly cost of $3 billion. One in five women is hospitalised, and surgery is needed in one in 10 cases. There are 26,000 ectopic pregnancies each year in the USA as a result of salpingitis, and 200,000 women are left infertile.
Symptoms can include:
PID is usually sexually transmitted, but gynaecological surgical procedures such as abortion or the insertion of an intra-uterine device (IUD) can cause infectious agents to spread upwards from the cervix and vagina. In Sweden it was found that 12% to 14% of all PID cases had been caused by gynaecological procedures within 6 weeks of admission.
IUDs may increase the risk of PID because the string attached to the device which extends down into the vagina acts as a wick for infection, allowing bacteria to ascend more easily into the upper genital tract. The relative risk of PID for sexually active young women using IUDs is 1.5 (i.e. a risk of PID one-and-a-half times greater than for young women not using IUDs). Those using barrier methods (i.e. condoms and diaphragms) have a relative risk of PID of 0.6 (i.e. the chance that they will acquire PID is about half that of those who do not use barrier methods).
The use of oral contraception appears to have a protective effect among sexually active young women with a relative risk of 0.3 (one-third the risk of those who do not use oral contraception). It is believed that the influence of progestogen on cervical secretions may prevent the ascent of microbes, as it does for sperm. However, these data were collected in the 1970s when higher dose pills were in use, and the protective effect of the currently more commonly used low-dose pills is not known.
PID can have devastating consequences. Salpingitis is the most frequent long-term complication because it can cause scarring of the tubes and infertility, making it impossible for the fertilised ovum to pass through the tube to the uterus.
One episode of PID doubles the risk of tubal infertility, and even a single attack can bring a seven fold increase in the chances of ectopic pregnancy. It has been estimated that one attack of PID carries a 20% risk of tubal blockage, rising to 30% after a second episode and as high as 75% after three or more episodes.
On the basis of these results it has been estimated that, of the theoretical group of women born in 1955, 15,000 per 100,000 would have had PID, and 2,000 per 100,000 would be infertile by their 30th birthday.
If untreated, PID can lead to chronic pain and sometimes severe disability.
Testing for the major causative organisms must be undertaken. However, sometimes laparoscopy (investigation by minor surgery) will be required to correctly diagnose PID.
Outpatient care may be sufficient for women with mild symptoms, but hospitalisation is necessary for women with more severe infection. Because PID can be caused by a wide variety of agents, drug treatments should be used that are active against a broad range of pathogens. Amoxycillin (penicillin) and doxycycline are usually prescribed.
It is imperative that male partners are tested and treated if necessary. In men symptoms can be mild or non-existent and they may not present for testing or treatment.
Indications for hospitalisation
There is no single or combination diagnostic indicator that reliably predicts pelvic inflammatory disease (PID). However general predictors of disease include
- barrier methods (condoms, diaphragms, vaginal spermicides) are associated with a decreased risk.
- Oral contraceptive pill (OCP) - increased risk of chlamydia, but a decreased risk of PID and no significant effect on the risk of tubal infertility.
- Intrauterine contraceptive device (IUCD) - relative risk of PID associated with IUCDs (excluding Dalkon Shield) appears to be highest in the first four months after insertion of the IUCD.
A combination of clinical and laboratory information is required. Symptoms alone are not a good predictor of PID, and clinical diagnosis alone is difficult.
On examination all of the following should be present
These findings may be sufficient for a diagnosis of PID in a woman with a mild presentation, at risk of STDs and in the absence of strong evidence for a competing diagnosis.
There should also be one of the following criteria suggesting genital tract infection or an inflammatory process. When symptoms are severe, other diagnoses should be considered, and more than one of the following criteria should be present to make a diagnosis of PID.
The definitive criteria for diagnosing PID include the following:
Two objectives of antimicrobial therapy:
There is consensus that PID is polymicrobial. Neisseria gonorrhoeae and Chlamydia trachomatis are implicated most often. In addition, a variety of endogenous anaerobic and aerobic bacteria have been isolated from women with PID and may also be causative agents of disease. Treatment is usually initiated empirically before a microbial cause is established.
Outpatient therapy
The following combination regimen should be used. If ongoing parenteral treatment is required, the woman should be hospitalised (see following section)
cefoxitin 2 g im as a single dose
plus
probenecid 1 g orally as a single dose
plus
doxycycline 100 mg orally twice daily for 14 days
plus
metronidazole 400 mg orally twice daily for 14 days
CDC guidelines (MMWR 1998; 47 [No. RR-1] pp79-86) recommend hospitalisation when
Other criteria for hospitalisation which have been considered include
It is common practice to remove an IUCD once PID has been diagnosed, but the effect on the acute infection by doing so is unclear.
Since women with PID are at high risk of a further episode of PID, the IUCD is probably not an appropriate contraceptive.
When a tubo-ovarian abscess is present therapeutic levels of appropriate parenteral antibiotics should be achieved before the IUCD is removed.
Against this background Clinic 275 policy is to remove the IUCD 48 hours after commencement of therapy for gonorrhoea or chlamydial infection, unless there are mitigating circumstances which pose a greater risk than that of PID, eg a likely absconder with a high risk of having an unwanted pregnancy before adequate contraception can be arranged.
Regular sex partners of all women with PID should be evaluated for STD and treated empirically for chlamydia and/or gonorrhoea even when there are no symptoms of disease.
Complications may occur in spite of adequate treatment. There are uncertainties regarding the effectiveness of antimicrobial therapy in totally eradicating tubal infection, even where cervical infection has been eliminated. Delay in diagnosis and treatment, or inadequate treatment may also increase the rate of complications. Complications include
see also:Chlamydial Infection