Pelvic Inflammatory Disease Workup

A number of procedures can be performed to improve the diagnosis of pelvic inflammatory disease (PID) and its complications. These procedures are not necessary, nor are they indicated, in the management of every case of PID. However, due to the difficulty of definitive clinical diagnosis and the number of important surgical and gynecologic emergencies that may have similar presentations, the clinician should be aware of these modalities. Specific criteria for PID based on procedures that may be appropriate for some patients are as follows:

• Laparoscopic confirmation
• Transvaginal ultrasonographic scanning or magnetic resonance imaging (MRI) showing thickened, fluid-filled tubes with/without free pelvic fluid or tubo-ovarian abscess (TOA)
• Endometrial biopsy showing endometritis

Laparoscopy is the criterion standard for the diagnosis of PID, but the diagnosis of PID in emergency departments and clinics is often based on clinical criteria, with or without additional laboratory and imaging evidence.^[32] No single test is highly specific and sensitive for PID, but laboratory tests, imaging studies, and procedures may be used to increase the specificity of the diagnosis.

Additional criteria that improve diagnostic specificity include the following:

• Oral temperature greater than 38.3° C (101° F)
• Abnormal cervical or vaginal mucopurulent discharge
• Abundant white blood cells (WBCs) on saline microscopy of vaginal secretions
• Elevated erythrocyte sedimentation rate
• Elevated C-reactive protein
• Laboratory evidence of cervical infection with N gonorrhoeae or C trachomatis (culture or DNA probe)

Perform a pregnancy test. If the results are positive, the possibility of ectopic pregnancy must be addressed. This also directly influences antibiotic choice and consideration of the patient for admission.

On a complete blood count (CBC), less than 50% of women with acute PID have a WBC count above 10,000. Due to the poor sensitivity and specificity, an elevated WBC count is not a CDC criterion for diagnosing PID.

In fact, no single test is highly specific and sensitive for PID; however, a number of tests may be used to increase the specificity of the clinical diagnosis. Saline and potassium hydroxide–treated preparations of vaginal secretions can be examined for leukorrhea (>10 WBC/high-power field, >1 WBC/epithelial cell), trichomoniasis, and clue cells.^{[5, 33]} The presence of leukorrhea was found to be the most sensitive, but not specific, laboratory indicator of upper tract infection; the absence of leukorrhea is a negative predictor of PID.

Other nonspecific findings include elevation of the erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), or WBC count.

Gonorrhea DNA probes and cultures are generally used to support the diagnosis and to provide epidemiologic data for public health departments, but they are frequently negative in later stages. Chlamydial DNA probes and cultures are generally used to support the diagnosis and to provide epidemiologic data for public health departments, although there is large variability in recovery from the cervix (5-56%). Quantitative culture for chlamydia identifies rapidly replicating bacteria that appear to be associated with active disease. However, DNA probe and culture results are often not available to the emergency physician at the time of initial evaluation.

One study suggested that women with a high titer of IgG chlamydial antibodies, acute pelvic pain, and a clinical picture suggestive of PID were more likely to have salpingitis than adhesions alone. Those patients with high titers and chronic pelvic pain, but with a clinical picture that did not suggest PID, were more likely to have adhesions alone. The investigators concluded that their limited data suggested that serologic testing might help to formulate the diagnosis.^[34]

Other tests that may be considered include the following:

• Rapid protein reagin (RPR) test for syphilis (syphilis is again increasing in the United States)
• Hepatitis and HIV
• Urinalysis to help exclude urinary tract infections (however, a positive urinalysis does not exclude PID, because any inflammatory process in the contiguous pelvis can produce white blood cells in the urine)

Blood cultures are not helpful in the diagnosis of PID.

Ultrasonographic scanning is one diagnostic imaging examination performed in cases of suspected PID in which clinical findings are nondiagnostic. Transvaginal ultrasonography is superior to transabdominal ultrasonography for diagnosing PID, as well as endometrial abnormalities and pelvic masses.^[33] This modality is readily available and noninvasive and can be performed at the patient's bedside. There are no large randomized trials addressing the specificity and sensitivity of bedside ultrasonography in PID diagnosis. The literature demonstrates that the sensitivity and specificity depend on the criteria used to indicate PID, the quality of the equipment, and the experience of the individual operator performing the test.

Transvaginal ultrasonography has poor sensitivity (81%) and specificity (78%) in mild or atypical PID.^[33] Helpful findings include thickened (>5 mm), fluid-filled fallopian tubes; indistinct endometrial borders; ovaries with multiple small cysts; and moderate-to-large amounts of free pelvic fluid in acute, severe PID. Small amounts of free pelvic fluid have not been shown to be a discriminatory finding. These findings alone do not demonstrate adequate specificity to make a definitive diagnosis of PID.

In the patient who appears toxic or has asymmetric pelvic findings, ultrasonographic scanning is an important diagnostic tool for the identification of a TOA. Pelvic abscesses may be seen as complex, adnexal masses with multiple internal echoes. The modality has been shown to demonstrate as many as 70% of adnexal masses missed on physical examination.

Pelvic ultrasonographic scanning (see the images below) is also useful in evaluating the possibility of ectopic pregnancy in patients whose differential diagnosis includes that condition and PID. The modality can also be helpful in evaluating other disorders in the differential diagnosis, including hemorrhagic ovarian cyst, ovarian torsion, endometrioma, and appendicitis. The use of ultrasound appears to be medical center specific, as some adult academic medical centers do not believe that ultrasound is of appropriate sensitivity and specificity to be used as a solo imaging modality to rule out appendicitis.

Ultrasonographic results in patients with PID may be normal or nonspecific, because salpingitis alone is not usually associated with imaging findings.^[35]

Positive ultrasonographic findings in PID may include the following:

• The uterus may be ill defined because of inflammation; however, inflammation of the uterus is an unusual finding
• Endometritis may result in central-endometrial-cavity echo thickening and heterogeneity
• Hydrosalpinx is depicted as a fluid-filled fallopian tube (if the fallopian tube walls are thickened and if debris is present within the tube, pyosalpinx should be considered in the differential diagnosis, but a pyosalpinx may be imaged as an echoless tube, whereas an imaged echo-filled tube may be due to proteinaceous but noninfected fluid in a hydrosalpinx)
• Oophoritis results in enlarged ovaries with ill-defined margins that often appear adherent to the uterus; adjacent free fluid may be present in the adnexa or cul-de-sac
• Tubo-ovarian abscesses (TOAs) are depicted as complex adnexal masses with thickened walls and central fluid
• Pelvic infection, such as tubal hyperemia, detected by Doppler studies, is one of the most specific criteria in diagnosing PID.^[36]

Thickening of the endometrium is nonspecific for PID because this finding may also be seen with endometrial hyperplasia, polyps, or cancer. Knowledge of the patient's clinical findings and other signs of infection can help in the differential diagnosis.

Hydrosalpinx and pyosalpinx can usually be readily distinguished from pelvic veins and bowel by visualizing the color flow within the patent blood vessels and peristalsis within the bowel.

Imaging findings in TOAs are usually nonspecific and must be distinguished from endometriomas, ectopic pregnancies, hemorrhagic cysts, ovarian tumors, and abscesses from adjacent organs.

Laparoscopy is the criterion standard for the diagnosis of PID. It is significantly more specific and sensitive than are clinical criteria alone. The minimum criteria to diagnose PID laparoscopically include tubal wall edema, visible hyperemia of the tubal surface, and the presence of exudate on the tubal surfaces and fimbriae.

Pelvic masses consistent with tubo-ovarian abscess or ectopic pregnancy can be directly visualized. Hepatic abscess exudate and/or adhesions may be visible. Material can be obtained for definitive culture and histologic studies.

Drawbacks of laparoscopy are that the procedure is expensive and invasive, exhibits interobserver variability, and requires an operating room and anesthesia.^[29] Findings on laparoscopy do not necessarily correlate with the severity of illness, as only the surfaces of structures are visible. Laparoscopy may not fully define PID in up to 20% of cases.

Computed tomography (CT) scanning may also be used as the initial diagnostic study for the investigation of nonspecific pelvic pain in a female, and PID may be found incidentally. Ultrasonographic imaging is preferred over CT scanning as the triaging tool in a female child or adolescent with right lower quadrant or pelvic pain, because of concerns about radiation exposure.

CT scan findings are nonspecific in cases of PID in which there is no evidence of an abscess. Inflammation obliterates the pelvic fat planes, with thickening of the fascial planes. If hydrosalpinx is present, a fluid-filled tubular structure may be seen in the adnexa.

Typically, a TOA is visualized as a mass; the mass may have regular margins and contain debris similar to that seen in endometriomas or hemorrhagic cysts. The margins may be thick and irregular. There may also be an associated low-attenuation area that may represent an adjacent or contained fluid-filled fallopian tube.^[37] Many adult centers also prefer this modality to ultrasonography when a diagnosis of appendicitis is in question.

Tubular, fluid-filled, nonvascular structures in the pelvis that are associated with an adnexal mass are suggestive of dilated fallopian tubes that correlate with cases of PID. A finding of an adjacent or surrounding complex mass confirms the diagnosis of TOA.

Although the specificity (95%) and sensitivity (95%) of magnetic resonance imaging (MRI) are relatively high,^[33] the modality is costly and rarely indicated in acute PID.

Hydrosalpinx is depicted as a tubular structure with low signal intensity on T1-weighted MRI scans and high signal intensity on T2-weighted images. If the walls are thickened, pyosalpinx should be considered in the differential diagnosis.^[38]

Oophoritis may be evidenced by enlarged, polycystic-appearing ovaries with ill-defined margins and adjacent fluid.

TOAs often appear as thick-walled masses with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Occasionally, the TOA may be isointense or hyperintense on T1-weighted images, and they may have heterogeneous signal intensity on T2-weighted images.

Culdocentesis can be performed rapidly in the emergency department. With the advent of transvaginal ultrasonographic scanning, culdocentesis is rarely performed, but it is valuable in settings where current technology is unavailable. For the procedure, an 18-gauge spinal needle attached to a 20-mL syringe is inserted transvaginally into the cul-de-sac. Normally, this yields only 2-4 mL of clear to straw-colored free pelvic fluid; purulent fluid indicates an infectious or inflammatory process. The potential positive findings of leukocytes and bacteria are nonspecific and may indicate PID or may be a product of another infectious or inflammatory process in the pelvis, such as appendicitis or diverticulitis, or may be due to contamination with vaginal contents. A yield of more than 2 mL of nonclotting blood is consistent with ectopic pregnancy.

Endometrial biopsy can be used to determine the histopathologic diagnosis of endometritis, a condition that is uniformly associated with salpingitis. Endometrial biopsy is approximately 90% specific and sensitive. The procedure is performed with an endometrial suction pipette/curette and is well tolerated. Specimens for culture may also be obtained during the procedure, but these are frequently contaminated with vaginal flora.

The 2010 update to the CDC sexually transmitted diseases treatment guideline recommends endometrial biopsy in women undergoing laparoscopy who have no visible signs of salpingitis, since endometritis can be the only sign of PID.^[36]

Diagnostic use of endometrial biopsy in the emergency department is limited due to the requirement for operator training. In addition, results are not immediately available to the clinician.