Diagnosis of Endometriosis

Robert Z. Spaczynski, MD, PhD, Antoni J. Duleba, MD

Disclosures

Semin Reprod Med. 2003;21(2) 

In This Article

Imaging Techniques

Selective use of imaging studies may be helpful in identifying patients with endometriosis. Detection of large endometriotic implants and endometriomas may be accomplished by transvaginal ultrasonography and magnetic resonance imaging (MRI). Other techniques, such as computed tomography, while occasionally helpful in localizing lesions, often yield nonspecific findings.

Ultrasound

Ultrasonographic examination is the most common imaging modality used to evaluate women suspected of having endometriosis. Ultrasound is particularly helpful in the evaluation of endometriotic cysts but has a limited role in the diagnosis of adhesions or superficial peritoneal implants.[120] Transvaginal ultrasound should be performed preferably using high-frequency probes (6-7.5 MHz) and with the aid of color Doppler imaging. In selected cases, such as abdominal wall endometriosis and bladder endometriosis, a transabdominal approach may also be useful.[121,122]

Ultrasonographic features of endometriomas are diverse. Usually, they present as cystic structures with diffuse low-level internal echoes (95%) and echogenic wall foci.[123,124] Occasionally, endometriotic cysts may have septations, thickened walls, and wall nodularity. Diagnostic performance of ultrasound in the detection of endometriomas was reported to have up to 92% sensitivity and 99% specificity ( Table 3 ).[178,179] Diagnostic accuracy of ultrasound may be enhanced by color Doppler flow studies. Blood flow in endometriomas is usually pericystic, especially noticeable in the hilar region, and usually visualized in regularly spaced vessels.[125] Kurjak and Kupesic[125] demonstrated excellent results with the application of a scoring system based on clinical parameters, CA-125 levels, and sonographic and color Doppler flow characteristics. However, these observations were not reproduced by others, possibly due to differences in clinical characteristics of the populations studied.[126]

There is also controversy regarding the presence of endometrioma vascularization, reported to range from 31 to 98%.[125,127,128] Alcazar[129] found that in patients with pelvic pain vascularization of ovarian endometriomas is higher and the pulsatility index is lower than in asymptomatic patients. Improvement in diagnostic accuracy may be achieved with the introduction of power Doppler, which allows detection of low-velocity flow.[127]

Dermoid cysts, hemorrhagic cysts, and cystic neoplasms may resemble endometriomas and must be considered in the differential diagnosis.[123,124] The application of three-dimensional ultrasound may allow better visualization of the topography of the surface and internal echoes as well as the vasculature of cystic ovarian tumors. More detailed information obtained with the three-dimensional technique may result in more accurate ultrasound performance and better differentiation of endometriomas from other benign and malignant masses.[130,131]

Transrectal ultrasonography was reported to be a useful tool in the diagnosis of deep infiltrating endometriosis. The use of rectal ultrasound with a 6.5-MHz biplane convex probe had a sensitivity of 97% and 80% and a specificity of 96% and 97% in detection of rectovaginal endometriosis and uterosacral ligament infiltration, respectively, as confirmed by surgery and histopathological findings.[132] Infiltration of the intestinal wall by endometriosis was identified by endoscopic rectal ultrasonography (EUS) using 7.5- and 12-MHz radial probes.[133,134] This technique allows circumferential imaging of the rectum and surrounding areas and had a reportedly positive predictive value of 100% in the detection of rectal wall involvement.

Magnetic Resonance Imaging

MRI is particularly helpful in identification of endometriomas. Occasionally, it may also visualize solid endometriotic implants and adhesions. It is an adjunctive noninvasive examination, useful in a preselected, high-risk population.

Endometrial implants are often small and their signal intensity is variable. They usually express an intensity similar to that of normal endometrium -- hypointense on TI- and hyperintense on T2-weighted images -- but may also be hypo- or hyperintense on both TI- and T2-weighted images. Small endometriotic implants are difficult to visualize.[135,136] Some improvement may be achieved with application of the TI-weighted fat suppression technique.[137] Theoretically, implants may be enhanced using contrast medium (gadolinium); but use of this technique failed to improve sensitivity or specificity of MRI in the detection of endometriosis.[138] MRI may also occasionally be suggestive of dense adhesions in the presence of a distortion of the adjacent bowel and in the absence of a detectable interface between the ovary and the surrounding anatomic structures.[135]

MRI is most useful in identification of endometriomas and it has a sensitivity and specificity comparable to or greater than those of transvaginal ultrasound; however, direct comparisons of MRI with ultrasound in the same population of patients are not available ( Table 4 ). Identification of endometriosis by MRI relies on detection of pigmented hemorrhagic lesions. Endometriomas have a relatively homogeneous high signal intensity on TI-weighted images because of degenerated blood products, including methemoglobin and deoxyhemoglobin. A characteristic feature of an endometrioma is "shading" -- hypointense signal on T2-weighted images. High concentrations of iron and protein accumulated in endometriotic cysts result in cross-linking of proteins and a subsequent decrease in T2 relaxation time. Signal characteristics vary according to the age of hemorrhage, and endometriomas may have a mixed spectrum of appearances. Acute hemorrhage may be associated with hypointense TI- and T2-weighted images, whereas old hemorrhage may result in hyperintensity of both TI- and T2-weighted images. A hypointense rim of endometrioma may be due to a fibrotic cyst wall combined with hemosiderin-laden macrophages.[135,136,139,140]

Excellent diagnostic performance of MRI was reported by Togashi et al.[141] A diagnosis of endometrioma was best accomplished not only in the presence of hyperintense TI- and hypointense T2-weighted images but also when multiple hyperintense lesions were observed on TI-weighted images regardless of their signal intensity on T2-weighted images. In addition to using routine imaging, a TI-weighted fat-suppressed image improves diagnostic accuracy.[138,142] Administration of gadolinium-based contrast medium resulted in a variable enhancement of the endometrioma wall and was not helpful in differentiation from other cysts.[138]

Pelvic magnetic resonance may also be useful in monitoring the effects of medical therapy as well as in predicting treatment outcome in patients with endometriomas prior to therapy initiation.[143,144,145] Furthermore, MRI may be useful in detection of nerve invasion (e.g., sciatic endometriosis) and abdominal wall lesions.[80,81,146]

MRI was reported to be valuable in the diagnosis of extraperitoneal endometriotic lesions, especially in the rectovaginal septum. Kinkel et al[147] described the use of MRI in the identification of subsequently histopathologically demonstrated deep endometriosis. They concluded that MRI was able to detect infiltrations of the uterosacral ligaments on T2-weighted images with 100% sensitivity. MRI was also helpful in the diagnosis of bladder and cul-de-sac endometriosis but had unsatisfactory sensitivity in the detection of rectal lesions.[147] The reliability of MRI in the assessment of deep endometriosis was achieved with the introduction of new technologies, particularly endocavitary and phased-array coils.[122,147] In rare instances, MRI may be helpful in identification of hepatic and rectal endometriotic lesions.[68,148]

Other Imaging Techniques

Various additional imaging procedures may be occasionally useful in the diagnosis of endometriosis. Computed tomography can detect lesions in pleura, brain, and other uncommon locations.[75,79] Barium enema, especially with double contrast, can demonstrate bowel infiltration.[65,149] If bladder or ureteral involvement is suspected, intravenous pyelography, cystoscopy, or ureteroscopy may be performed.[71,150] However, the findings of these techniques are nonspecific and are usually compatible with other conditions such as various inflammatory processes or neoplasms.

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