What is the differential diagnosis of endometrioma ?
1. hemorrhagic cysts also appear hyperintense on T1-weighted images, but typically do not have T2 shading (they are typically bright on T2-weighted images) and T2 dark spot 2. ovarian dermoid cysts also appear hyperintense on T1-weighted images, but signal loss on fat-saturated sequences 3. cystic neoplasms show heterogeneous T1 signal and enhancement 4. tubo-ovarian abscess presents as a T1 hypointense lesion and T2 heterogeneous to hyperintense signal, with wall and surrounding soft tissue enhancement
How to describe the T2 dark spot sign ?
T2 dark spot sign is defined as a hypointense focus on T2-weighted images. It is a marker of chronic haemorrhage (haemosiderin-laden macrophages and fibrous component).
How to describe the Shading sign?
Shading sign is due to repeated haemorrhage, endometriomas show hyperintense on T1-weighted sequences with varying levels of hypointensity on T2-weighted sequences (complete loss of signal intensity or hypointense layering fluid level).
Left adnexal lesion shows high T1 signal on fat suppressed sequence, T2 dark spot sign and T2 shading.
Right adnexal lesion shows high T1 signal on fat suppressed sequence, and T2 shading with elongated lobular appearance, suggestive of haematosalpinx.
Minimal fluid is seen in vesicouterine pouch.