Thoracic endometriosis syndrome: imaging findings and the value of a dedicated MRI protocol

Endometriosis is the presence of hormonally sensitive endometrium-like tissue outside the uterus. It is a common condition, affecting 10% of reproductive-age people assigned as female at birth. Although usually occurring in the pelvis, it can rarely involve the thoracic cavity and diaphragm which is termed thoracic endometriosis. Thoracic endometriosis syndrome (TES) refers to four well-recognized clinical entities: catamenial pneumothorax, catamenial hemothorax, catamenial hemoptysis, and lung nodules. However, TES presentation can also be nonspecific, even absent. Optimal management is multidisciplinary, as it depends on patient presentation and lesion characteristics. While initial imaging of thoracic symptoms is with chest radiography and computerized tomography, these modalities have inferior soft tissue contrast resolution and tissue characterization compared to magnetic resonance imaging (MRI), especially for the detection of both hematic and cystic endometriotic implants. Therefore, a dedicated MRI protocol is essential for diagnosing thoracic endometriosis and aiding surgical planning. Considering the dome-shaped morphology of the diaphragm, sagittal and coronal projections can improve visualization of tiny endometriotic plaques or deposits that are inconspicuous on the axial plane. Breath-hold and respiratory-triggered or navigated techniques are critical for mitigating motion artifacts. T1-weighted fat-suppressed sequences are important for identifying intrinsic T1 hyperintensity and blood products associated with endometriotic lesions. T2-weighted fat-suppressed sequences increase sensitivity for cystic or vesicular tissue. Diffusion-weighted and postcontrast imaging can help diagnose alternative causes of symptomology, including malignancy.