Research

A 22-year-old non-gravid lady presented to our facility with left lower abdominal pains of several months duration which gets worse during her menstrual periods. Transvaginal ultrasonography revealed a large probe-tender smoothly-marginated unilocular thick-walled oval cystic mass replete with fine echogenic debris, giving the ‘groundglass’ appearance in the left ovary. The cyst measured 6.4×6.5×6.2cm (estimated volume of 136.4mls). A diagnosis of unilocular left ovarian endometrioma was made. Patient opted for minimally invasive management using ultrasound-guided drainage and sclerotherapy, which were done at our center, with immediate relief of her pain and discomfort. The picture above shows the fresh whole bloody fluid being aspirated from the cyst after guiding the needle into the cyst under aseptic technique, using ultrasound guidance and local anaesthesia.   An amount of the aspirate was collected in a sterile bottle and sent for cytology and microbiological analysis, and patient was referred to a gynaecologist for further management.   DISCUSSION: ENDOMETRIOMA   Epidemiology  These occur in up to 10% of women of reproductive age.   Clinical presentation  The symptoms do not necessarily correlate with disease severity and include pelvic pain, dysmenorrhea, dyspareunia and infertility in 30-40% of patients.   Pathology  Although the pathogenesis is still under discussion, three theories have emerged: Metaplastic transformation of the peritoneal epithelium into functional endometrium Peritoneal seeding due to retrograde menstruation Activation of mesenchymal cells differentiation caused by endometrium in the peritoneal cavity from retrograde flow. Endometriomas contain dark degenerated blood products following repeated cyclical hemorrhage. The cysts may be up to 20 cm in size although they are usually smaller (2-5 cm). Because ovarian endometriomas contain ectopic endometrial glands and stroma, they are hormonally responsive and can undergo decidualisation in the progestational state of pregnancy. During pregnancy, an endometrioma may show decidualised stroma with increased secretory activity, prominent stromal vascularity and edema, a process termed a decidualised endometrioma 15.   Location Typical locations include: ovaries: ~75% anterior/posterior cul-de-sac: ~70% posterior broad ligament: ~50% uterosacral ligaments: ~35% uterus: ~10% colon: ~5% Radiographic features  Plain radiograph  Not usually helpful in diagnosis. ~10% of endometriomas can calcify.   Ultrasound  The appearances of endometriomas can be quite variable. The classical example is an avascular unilocular cyst containing low-level, homogeneous “ground-glass” like internal echoes, as a result of the hemorrhagic debris. This appearance occurs in 50% of cases 7. The kissing ovaries sign may be seen in case of bilateral endometriomas. Less typical features include 7: multiple locules (~85% will have <5 locules) hyperechoic wall foci (present in 35%) due to cholesterol deposits  cystic-solid lesion (~15%) or purely solid lesion (1%) anechoic cysts (rare: 2%) fluid-fluid level 10  Computed Tomography (CT)  CT is not the preferred imaging modality to assess endometriosis, as image findings tend to be non-specific, nevertheless often patients will undergo CT for acute abdominal pain. Endometriomas on CT tend to be complex pelvic cystic masses often with increased attenuation components representing haemorrhage. These appearances are non-specific also being seen with haemorrhagic ovarian cysts or neoplasms. Bilateral lesions points towards endometriomas but again maybe seen with other entities, such as a tubo-ovarian abscess or neoplasm 10.   Magnetic Resonance Imaging (MRI)  Signal characteristics vary according to the age of any complicating hemorrhage 6: T1 typically, lesions appear hyperintense while acute haemorrhage occasionally appears hypointense endometriomas with high T1 signal characteristically 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 T2 typically hypointense owing to the presence of deoxyhaemoglobin and methaemoglobin (shading sign), which is very suggestive of an endometrioma 3 T2 dark spot sign is specific for chronic haemorrhage and is helpful in diagnosing endometriomas 9 old haemorrhage occasionally appears hyperintense DWI/ADC variable restricted diffusion T1 C+ (Gd) may have wall enhancement the presence of an enhancing mural nodule is suggestive of malignant transformation Decidualised ovarian endometrioma is considered a rare phenomenon in pregnancy, with only a limited number of cases described in the literature. On imaging, these lesions may demonstrate wall thickening, smoothly lobulated mural nodules or intracystic papillary projections and increased internal vascularity, closely mimicking borderline or malignant ovarian tumours and making confident differentiation challenging in some cases 15.   Treatment and prognosis  Although endometriomas are usually benign entities, there is an ~1% rate of malignant transformation. Endometrioid tumours of the ovary and clear cell ovarian carcinomas are the most common histological patterns seen 8. They are mostly seen in women >40 years after several years of latency, with endometriomas larger than 9 cm 4,5. Malignant transformation is uncommon in masses <6 cm. If not surgically excised, follow-up should be at least yearly 4. GnRH agonists may be used for medical management. Endometriomas have the potential to decidualise during pregnancy resulting in the formation of vascularized, papillary projections13 (solid internal components with flow on colour doppler). Although rare, these changes give an appearance mimicking malignancy and careful follow-up imaging is recommended. Ovarian endometriomas carry a lower risk of ovarian torsion than other ovarian cysts due to their frequent association with adhesions 14.   Differential diagnosis  General imaging differential considerations include: haemorrhagic ovarian cyst brighter on T2-weighted images absence of the “shading sign“ ovarian dermoid cyst will show fat suppression on MRI fat-suppressed sequences cystic neoplasm tubo-ovarian abscess