Differentiating between endometriomas and ovarian hemorrhagic cysts on magnetic resonance imaging (MRI) is an important aspect of gynecological imaging.
This pictorial review will provide a detailed textual description of the key features and characteristics that can aid in this differentiation.
It is essential to note that while MRI can be highly informative, a definitive diagnosis often requires a combination of clinical information, imaging findings, and sometimes, histopathological confirmation.
Introduction Endometriomas and ovarian hemorrhagic cysts are two common pathological entities that can present as ovarian cystic lesions in women.
They have distinct etiologies and clinical implications.
Accurate differentiation between them is essential for appropriate management and treatment planning.
Endometriomas: Endometriosis is defined as the presence of functional endometrial glands and stroma outside the uterine cavity and myometrium.
This ectopic tissue is hormonally responsive and may undergo bleeding, inflammation, fibrosis, and adhesion formation, leading to pelvic pain and infertility.
It usually affects women of childbearing age and is estimated to affect approximately 5–10% of the female population.
Peak incidence is in the third decade.
The symptoms depend on the localization of the endometriosis, the depth of the infiltration, and whether the endometriosis is complicated by adhesions.
It is divided into: - Superficial endometriosis - multiple superficial plaques may be seen scattered in the peritoneum and pelvic ligaments - Deep endometriosis - penetrating into the retroperitoneal space or the wall of the pelvic organs to a depth of at least 5 mm, and comprises nodules, cysts, and secondary scarring - Endometriotic cysts - most commonly occur in the ovaries and are the result of repeated cyclic hemorrhage within a deep implant The most common location is in the ovaries, following the pelvic peritoneum.
Less common locations include deep subperitoneal tissues, C-section scars, gastrointestinal tract, bladder, chest, and subcutaneous tissues.
The most common pelvic sites of involvement are the pouch of Douglas, uterosacral ligament, and torus uterinus.
Ever since 2022 diagnostic laparoscopy has been the gold standard.
The 2022 updated endometriosis guidelines from the European Society for Human Reproduction and Embryology guidelines now recommend imaging to be used as a front-line diagnostic test.
MRI has high sensitivity (90%) and specificity (91%), whereas transvaginal ultrasound has been shown to have sensitivities and specificity above 90% for deep endometriosis, depending on location.
On transvaginal ultrasound, endometriotic nodules in deep pelvic endometriosis appear as solid, hypoechoic, irregular masses.
They may contain echogenic foci or small cystic spaces and often show little or no blood flow on color Doppler.
Endometriomas present as unilocular cystic lesions containing uniform low-level echoes, with no blood flow on color Doppler (Fig 1.).
If they are bilateral, ovaries can be adherent to one another posterior to the uterus which is called ‘kissing’ ovaries sing (Fig 2.).
Unlike many other ovarian cysts, endometriomas do not typically resolve.
MRI has greater specificity for the diagnosis of endometriomas than any other non-invasive imaging technique.
Generally, the lesions that can be detected with MRI are those that contain blood products.
These cysts typically have specific MRI characteristics: • T1-Weighted Imaging (T1WI): Endometriomas tend to be hyperintense on T1WI.
This is due to the presence of old blood products and hemosiderin within the cysts.
The hemosiderin has paramagnetic properties that result in a shortened T1 relaxation time, leading to hyperintensity.
This hyperintensity on T1WI can be likened to the "chocolate cyst" appearance, as the contents resemble chocolate syrup.
They do not have signal loss on T1 fat-suppressed sequences, which is important for differentiating it from a mature cystic teratoma of the ovary.
In acute hemorrhage, they appear hypointense. • T2-Weighted Imaging (T2WI): Endometriomas often exhibit a characteristic "T2 shading" appearance.
It consists of low signal (T2 shortening) affecting variable portions of the cyst.
It may involve only a small portion of the cysts, typically layering dependently, or the entire cyst.
The signal is due to the high concentration of protein and iron within the endometrioma resulting from recurrent hemorrhage (Fig 3.).
T2 dark spot is specific for chronic hemorrhage and is useful in diagnosing endometriomas (Fig 4.). • DWI/ADC variable restricted diffusion • T1 Fat Suppression: Endometriomas do not typically contain fat, so the signal remains hyperintense (Fig 5.). • T1 C+: May have wall enhancement on post-contrast images.
The presence of an enhancing mural nodule is suggestive of malignant transformation.
Ovarian Hemorrhagic Cysts: Ovarian hemorrhagic cysts, also known as hemorrhagic corpus luteum cysts or hemorrhagic follicular cysts, result from bleeding into a pre-existing ovarian cyst.
Radiographic features are variable depending on the age of the hemorrhage.
They typically resolve within 8 weeks.
Patients may feel a sudden onset of pelvic pain, can have a pelvic mass, or may be asymptomatic and the hemorrhagic ovarian cyst is then an incidental finding.
On transvaginal ultrasound, they can have a variable appearance depending on the stage of evolution of the blood products and clot.
A cyst with lace-like reticular echoes or an intracystic solid clot can be present.
They usually have a thin wall, but sometimes a clot may adhere to the cyst wall mimicking a nodule.
The nodule does not have a blood flow on Doppler imaging and a clot has concave borders.
Posterior acoustic enhancement may be present.
On MRI ovarian hemorrhagic cysts may have variable signal intensity on both T1 and T2-weighted images due to the presence of blood products at various stages of degradation.
They are usually hyperintense on T1 and T2- weighted images and do not show loss of signal on T1 fat-suppressed sequences, which is important for differentiating it from a mature cystic teratoma of the ovary, but very often they can be hypointense on T1-weighted images.
Hemorrhagic cysts may have a thickened cyst and do not enhance on post-contrast images.
Ovarian hemorrhagic cysts often change in appearance over time as the hemorrhage evolves and undergoes different stages of breakdown.
MRI examination Patient preparation includes: 1.
Patients should fast 3 to 6 hours before the exam to reduce the risk from vomiting and bowel movement artefacts. 2.
The use of an anti-peristaltic agent, unless contraindicated, is the most efficient way to limit bowel motion artefact 3.
A moderately filled bladder is optimal for the pelvic MRI.
MRI imaging sequences Basic protocol include: 1.
At least two T2W orthogonal oblique planes 2.
Axial T1W – the gold standard for the diagnosis of endometriotic cysts Additional sequences: 4.
T1W FS – to differentiate hemorrhagic from fatty lesions 5.
DWI - differentiation of endometriomas from hemorrhagic cysts with significantly lower ADC values in endometriomas when compared with hemorrhagic ovarian cysts at all b values 6.
SWI - the presence of signal voids reflecting acute to chronic hemorrhage are very sensitive in the diagnosis of extra-ovarian endometriosis, especially abdominal wall endometriosis 6.
Postcontrast T1W – gadolinium enhancement is crucial for depicting strongly enhancing mural nodules if atypical features suggest potential malignancy.
Secondly, endometriosis and pelvic inflammatory disease are two conditions that can be easily confused, hence, the presence of a strong wall enhancement within adnexal masses is useful to suggest pelvic inflammatory disease Differential Diagnosis: While the above features can help distinguish between endometriomas and ovarian hemorrhagic cysts, there can be some overlap in imaging characteristics.
Therefore, clinical context and additional imaging findings can be critical for a definitive diagnosis.
In some cases, surgical intervention or histopathological examination may be necessary for confirmation.
It is important to consider the patient's clinical history and symptoms when interpreting MRI findings.
Endometriomas are often associated with endometriosis-related symptoms such as pelvic pain, dysmenorrhea, and dyspareunia.
Ovarian hemorrhagic cysts, on the other hand, may be associated with acute pelvic pain and tenderness, especially if they rupture or bleed significantly.