Investigations
1st investigations to order
white blood cell count
Test
Consider at first consultation.
White blood cell count is a non-specific test for infection.
Result is not specific, but may increase index of suspicion for PID.
Result alone is unlikely to alter management.
Medium predictive value.
Result
elevated
polymorphonuclear cells on wet mount of vaginal secretions
Test
Indicated at first consultation.
Presence of vaginal polymorphonuclear cells confirms vaginal infection.
Absence of these cells on wet mount excluded histological endometritis more than 90% of the time in one study, with a negative predictive value of 94.5%.[3][29]
High positive predictive value but not specific for pathogens most likely to cause PID.
Result
present on smear
genetic probe or culture of vaginal secretions for Neisseria gonorrhoeae and Chlamydia trachomatis
Test
Should be performed at first consultation in any patient with suspected PID.
Specificity for these infections is 100%; however, other organisms can also cause PID.[1][22]
Negative culture does not eliminate possibility of upper genital tract disease, so treatment should be initiated in a patient with clinical symptoms, regardless of test results.[30]
Result
positive result indicates presence of organisms
Investigations to consider
serum erythrocyte sedimentation rate (ESR)
Test
Non-specific test for inflammatory process.
Usually only elevated in moderate or severe PID. Result of this test alone is unlikely to change management.
In a study of serum white blood cell counts, wet mount polymorphonuclear cells, and ESR in women with a clinical diagnosis of acute PID, no single laboratory test had good sensitivity and specificity. A negative result on all three tests effectively excludes PID.[3][24]
Result
elevated
transvaginal ultrasound
Test
Test is useful in confirming an uncertain diagnosis.
Less expensive than other imaging methods and less risky than other invasive tests.
In one study, colour Doppler flow identified all laparoscopically confirmed cases of acute PID, making it 100% sensitive for this diagnosis.[31]
Result
classic signs are tubal wall thickness >5 mm, incomplete septae within the tube, fluid in the cul-de-sac, and a cog-wheel appearance on the cross-section of the tubal view; may also see tubo-ovarian abscess
pelvic CT
Test
CT can be used to confirm an uncertain diagnosis. It is indicated in patients with diffuse pelvic pain, peritonitis, or difficult or equivocal ultrasound. It should be performed with both oral and intravenous contrast, as un-opacified bowel may be mistaken for an abscess.[28] Indicated if MRI is not available or if ultrasound is inconclusive or non-diagnostic. The risk of cumulative radiation exposure should be considered in young women undergoing repeat imaging.[32]
Result
subtle changes in appearance of pelvic fascial floor planes, thickened uterosacral ligaments, inflammatory changes of the tubes and ovaries, abnormal fluid collection; in progressive disease, reactive inflammation of surrounding pelvic and abdominal structures may be seen
pelvic MRI
Test
MRI is considered superior to ultrasound at diagnosing PID when there is a tubo-ovarian abscess, pyosalpinx, fluid-filled tube, and/or enlarged polycystic ovaries with free intrapelvic fluid. However, both ultrasound and CT are more cost effective than MRI. Therefore, MRI is rarely used and plays only a complementary problem-solving role.[28]
Result
may show thickened fluid-filled tubes, tubo-ovarian abscess, pyosalpinx
laparoscopy
Test
Laparoscopy is the preferred invasive method of diagnosis, allowing direct visualisation of the gynaecological and abdominal structures.
Laparoscopy enables specimens to be taken from the fallopian tubes and pouch of Douglas, and is particularly useful in obtaining a more accurate diagnosis of salpingitis and a more complete bacteriological diagnosis. Laparoscopy will not detect endometritis or subtle inflammation of the fallopian tubes. It should not be used as a routine diagnostic tool, especially when symptoms are mild or vague.[1]
Result
laparoscopic abnormalities consistent with PID
endometrial biopsy
Test
Can confirm the diagnosis of endometritis. Endometrial biopsy should not be used as a routine diagnostic test. It is indicated in women undergoing laparoscopy who do not have visual evidence of salpingitis.[1]
Result
histological appearance of endometritis
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