There are several reasons for this:

1. Chlamydial or gonorrhea may have passed directly into the reproductive organs without infecting the cervix first (ie they may have been carried into the reproductive organs by sperm).

2. Chlamydia or gonorrhea may have caused a cervical infection first, but the cervical infection may have been eradicated while infection remains in the fallopian tubes.

3. The PID can be caused by other bacteria (ie not chlamydia or gonorrhea).

Generally, research has shown that there is a poor correlation between bacteria found on the cervix and bacteria found in the fallopian tubes. For these reasons, cervical tests are most useful if they are positive, because they may indicate bacteria which might have caused PID, but a negative result does not rule out PID.

ULTRASOUND: This is a picture created by sound waves. An ultrasound cannot show infection (bacteria are too small to be seen), but it can show a thickening or mass, which could be caused by PID. A transvaginal ultrasound (a picture taken through the vagina) is a fairly accurate way to diagnose abscesses. It is important to know if an abscess is there, because this is a serious complication of PID which can cause serious long-term health consequences, and different and longer treatment may be needed. Transvaginal ultrasound, in combination with a serum pregnancy test, can also accurately diagnose ectopic pregnancies, a common and serious complication of PID.

VAGINAL TESTS: These include checking a sample of vaginal fluid for inflammatory cells, for bacterial vaginosis, and to determine the vaginal PH (an acidic PH is healthy). Swedish PID experts believe that if inflammatory cells are present in the vagina, the woman may have PID, but research establishing this as a reliable criteria hasn't been reported. An abnormal vaginal PH or bacterial vaginosis don't indicate if the woman does or doesn't have PID, but they do indicate a condition which might progress to PID (or which may have already done so).

ENDOMETRIAL BIOPSY: This is an office procedure which many believe will improve the accuracy in diagnosing PID without surgery. The basic idea is that a small piece of tissue is removed from the lining of the uterus, stained, and then examined under a microscope for signs that the body is fighting an infection (ie neutrophils, lymphocytes, plasma cells). This procedure has just begun to be tested and initial results are promising. Endometrial biopsy has a good correlation with the results of laparoscopy which is the surgical examination of the reproductive organs which is the most accurate way to diagnose PID.

However, inflammation in the lining of the uterus can be patchy and only a small sample is taken, so endometrial biopsy may miss some inflammation/infection. Also, a woman may have infection in her fallopian tubes, but no infection in the uterus. In this case, the PID would not be detected by an endometrial biopsy, even though pelvic infection was actually there. Thus, while a positive endometrial biopsy does indicate that a woman has PID, a negative endometrial biopsy does not rule out PID.

LAPAROSCOPIC DIAGNOSIS (SURGERY): Laparoscopy allows direct examination of the pelvic organs, so it is the most accurate way to diagnose pelvic infection. During laparoscopy, a general anesthetic is given, a small incision is made below the navel, carbon dioxide gas is used to inflate the abdomen, and a laparoscope (a lighted instrument through which the pelvic organs can be seen) is inserted into the abdomen. Laparoscopy allows the physician to see the state of the pelvic organs, to take cultures, and to take samples of tissue. During laparoscopy, a physician can see if other conditions are present, such as endometriosis or appendicitis, which are easily confused with PID. Another advantage of laparoscopy is that the practitioner can take cultures to indicate what bacteria are involved in the infection so that the most effective treatment can be given. Laparoscopy also allows the physician to see if there are complications such as abscesses, adhesions, or a spread of infection to other organs, so that appropriate treatment can be given.

Most experts recommend the use of laparoscopy to diagnose PID to ensure that all women with PID are promptly and accurately treated. A recent study has shown that laparoscopy is not expensive, because a lot of money is saved when incorrect diagnoses are avoided. In other words, if a clinical diagnosis is used, many women aren't treated until serious damage has occurred, and many women who actually don't have PID are treated unnecessarily for PID. Both of these errors are costly to the health care system and to women.