**5.2 Endometriomas**

Transvaginal sonography (TVS) is universally most frequently used imaging tool for evaluation of endometriomas. USG features of chocolate cysts are diverse. The classical appearance is that of a cystic structure with diffuse low level internal echoes and echogenic wall foci. The cyst may be unilocular or multilocular. It may contain thin or thick septa. Sometimes there may be wall nodularity. Wall nodularity if present requires further investigation to rule out malignancy. Imaging alone cannot exclude malignant neoplasm.

It is interesting to note that out of 20% of the endometriomas exhibiting wall nodularity, 35% had hyperechogenic wall foci (Patel et al). Effort should be made to distinguish between wall nodularity and the hyperechogenic foci within the wall. The latter when present in lesion with low level echoes and no features of malignancy is indicative of endometrioma.

Differential diagnoses of chocolate cyst include haemorrhagic cyst, dermoid cyst and cystic neoplasms. Dermoid cyst usually exhibit either echogenic shadow due to its fat content or acoustic shadowing due to calcium which aids in the diagnosis. To differentiate between haemorrhagic cyst and chocolate cyst can be a difficult task. The haemorrhagic cyst usually displays high level internal echoes within a thin walled cyst which may advance with time and emerge as a more complex cyst. Formation of fibrin may imitate thin septa but these lesions usually resolve on follow up.

The accuracy of USG can be further improved by color Doppler flow studies. Blood flow in the endometrioma is through the regularly spaced vessels running in the hilar region and the pericystic space.

MRimaging is another tool for identifying endometriomas. Due to the cyclical bleeding endometriomas contain blood products at different age. They are seen as bright or hyperintense lesions on T1 weighted image. On T2 they appear more hypointense or dark with foci of hyperintensity, imparting it the classical appearance of 'shading'. Shading is

Imaging Tools for Endometriosis: Role of Ultrasound, MRI

**5.6 Malignant transformation in endometriosis** 

**5.7 Scar endometriosis** 

tools is being non invasive method.

of US. Radiology 1999; 210: 739-745.

**6. Conclusion** 

**7. References** 

and Other Imaging Modalities in Diagnosis and Planning Intervention 445

improved with the use of phased array coils, endovaginal coils and rectal contrast enema. MRI features that can be helpful in diagnosis include thickening of the rectal wall correlated with specific symptoms clinically, low signal intensity on T2 weighted images, and

Endorectal sonography as dicussed earlier is superior to MR imaging for diagnosis of this

Malignant transformation in endometrioma is a rare well-known complication of endometriosis, occurring in a younger age group with estimated incidence is less than 1% of women with ovarian endometriosis. The common histologic types are endometrioid adenocarcinoma and clear cell carcinoma arising from glandular elements and rare form is endometrial stromal sarcoma occurs arising from stromal elements. Loss of the T2 shading effect is more commonly detected in malignant than in benign endometriomas. The postulated reasoning for this is dilution of haemorrhagic fluid by tumor secretions, although is not specific to malignant endometrial cysts. Enhancing mural nodules within a cystic mass is another feature of malignant change in endometriosis. Typically mural nodules are enhancing, T1-weighted low and variable T2-weighted signal intensities. Dynamic subtraction images with a gradient- echo sequence often improve nodule enhancement. Again, enhancing mural nodules within endometriotic cysts, although seen more commonly

in malignant endometriomas is not specific and has been reported in benign lesions.

diagnosis specially in context of myometrium along the surgical scar.

Solid endometriosis can also develop in a caesarian section scar. MRI is valuable in identifying these lesions. MRI characteristically shows high signal intensity on T1 and hypointensity on T2 weighted images. Fat saturated sequences are more helpful in the

The imaging techniques have revolutionized the pre operative diagnosis of endometriosis although the ultimate confirmation is by histopathology only. The major advantage of these

Gougoutas CA, Siegelman ES, Hunt J, et al. Pelvic endometriosis: various manifestations

Knonickx PR, Meulman C, Demeyere S, Lesaffre E, CornillieFJ. Suggestive evidence that

endometriosis is associated with pelvic pain. Fertil Steril 1991; 55: 759-765. Patel MD, Feldstein VA, Chen DC, Lipson SD et al. Endometriomas: diagnostic performance

pelvic endometriosis is a progressive disease, whereas deeply infiltrating

and MR imaging findings. AJR Am J Roentgenol2000; 175: 353-358.

occasionally the presence of punctuate hyperintense foci of haemorrhage.

entity. The deposits on bowel are seen as rounded hypoechoic areas.

effect of degenerated blood products present at different stage within the same cyst. It can range from subtle layering to a complete signal void (black).

Since both the haemorrhagic cysts and the chocolate cyst contain blood products, it can be difficult to distinguish between them except for the fact that hemorrhagic cysts do not display shading, are mostly unilocular and resolve on interval imaging. In contrast dermoid cysts are easily diagnosed on MRI since they lose the signals and become dark on fat suppressed sequences.

After contrast administration, the periovarian peritoneal surface of the cyst can be enhanced which can help in identification of torsion ovary. Endometrioma in an enlarged but poorly enhancing ovary with peripherally located follicles is suggestive of torsion ovary on MRimaging.
