Laparoscopy is considered the standard of care in the diagnosis of pelvic inflammatory disease (PID), but it has the disadvantage of requiring general anesthesia. Transvaginal ultrasonography, which is superior to abdominal ultrasonography in demonstrating evidence of PID, requires the presence of thickened, fluid-filled fallopian tubes to make the diagnosis of PID. Although computed tomography (CT) can identify complex tubo-ovarian abscesses and has proved useful in the diagnosis of PID, it has the disadvantage of exposing reproductive organs to ionizing radiation. Magnetic resonance imaging (MRI) may provide better images of the soft tissue than CT. Tukeva and associates evaluated the accuracy of MRI in the diagnosis of PID and compared its accuracy with that of transvaginal ultrasonography and laparoscopy.
The study included 30 consecutive patients admitted to the hospital because of symptoms of PID. Each patient was evaluated by means of transvaginal ultrasonography, followed by MRI 24 hours later. Laparoscopy was performed immediately after MRI. If an adnexal mass was present, surgical samples were obtained for histology. Laparoscopy confirmed PID in 21 (70 percent) of the 30 patients. Three of the nine patients without PID had tubal torsion. In the other patients without PID, laparoscopy revealed a simple cyst, a dermoid cyst, an endometrioma, a ruptured cyst and free pelvic fluid. One patient had no laparoscopic evidence of a gynecologic disorder.
MRI findings were consistent with the diagnosis of PID in 20 (95 percent) of the 21 patients with laparoscopically proven PID and in one of the nine patients without PID. MRI demonstrated an abscess in 11 of the 21 patients with PID. False-negative MRI findings occurred in only one patient. In this patient, MRI was thought to show an endometrioma and a hemorrhagic cyst; laparoscopy revealed an endometrioma and salpingitis. Conversely, false-positive MRI findings occurred in one patient; this patient was thought to have tubal torsion and pyosalpinx on MRI, but laparoscopy revealed tubal torsion and hydrosalpinx.
Transvaginal ultrasonographic findings were consistent with the diagnosis of PID in 17 (81 percent) of the 21 patients with laparoscopically proven PID and in two of the nine patients without PID. Of the latter two patients, one had an endometrioma and the other had tubal torsion. Three cases of PID were missed by transvaginal ultrasonography. Two of these patients were thought to have an ovarian tumor on ultrasonographic examination but at laparoscopy were found to have an abscess. In one patient, endometrioma was diagnosed by ultrasonography, but this patient was found at laparoscopy to have pyosalpinx in addition to endometrioma.
Overall, MRI had a sensitivity of 95 percent, a specificity of 89 percent and an accuracy of 93 percent in the diagnosis of PID. For transvaginal ultrasonography, the sensitivity, specificity and accuracy rates were 81 percent, 78 percent and 80 percent, respectively.
The authors conclude that MRI was useful not only for establishing the diagnosis of PID but also for detecting other processes responsible for the symptoms. Although it could be argued that transvaginal ultrasonography is far more cost-effective than MRI, the authors state that if proper therapy is initiated early in the disease course and if exploratory laparoscopy can be avoided on the basis of the MRI findings, then MRI could prove to be a cost-effective modality.
editor's note: The difficulty in accurately diagnosing PID has prompted the Centers for Disease Control and Prevention (CDC) to recommend that antibiotic therapy be initiated in any patient presenting with adnexal, uterine and cervical tenderness. According to the CDC, these signs are sufficient evidence of PID to justify antibiotic therapy. If no response occurs in 72 hours, the patient should be reevaluated, and laparoscopy should be considered. Whether use of MRI can help decrease the need for laparoscopy in patients suspected of having PID requires further study. Transvaginal ultrasonography has not been shown to be accurate as the sole imaging method for the diagnosis of PID, although it is widely used in the evaluation of patients presenting with pelvic pain suggestive of PID.—b.a.