ESUR female pelvis group approach to cystic female pelvic lesions

Cystic female pelvic lesions, whether of ovarian or non-ovarian origin, are prevalent in routine clinical practice, with the majority originating from gynaecological (ovarian) structures, ranging from functional cysts to malignant ovarian tumours. Despite the fact that we encounter these lesions in the course of our routine clinical work, arriving at an accurate diagnosis can often prove challenging due to the overlap of imaging appearances. Ultrasound is the primary imaging modality for the evaluation of most cystic female pelvic lesions, while MRI serves as a problem-solving tool. In cases that are more complex or equivocal, pelvic MRI proved to be particularly useful due to its superior soft tissue resolution, multiplanar imaging capability and non-invasive nature. In order to make an accurate diagnosis, it is crucial to have a comprehensive understanding of pelvic topographic anatomy, be familiar with possible differential diagnoses and include all relevant clinical data. The classification of ovarian cystic lesions was undertaken using the O-RADS MRI risk stratification system, which provides standardised language for communication between radiologists and clinicians. The objective of this review is to illustrate the spectrum of typical MRI characteristics of different cystic female lesions of both ovarian and non-ovarian origin, with the emphasis on differential diagnoses. The review includes tables with MRI appearances on T2, T1, DWI sequences and postcontrast tomograms. To facilitate the learning process, schematic representations of MRI appearances of ovarian lesions have been incorporated. CRITICAL RELEVANCE STATEMENT: MRI diagnosis of various ovarian and non-ovarian cystic female pelvic lesions and their differential diagnosis. KEY POINTS: The diagnosis of cystic female pelvic lesions can be challenging due to the overlapping imaging characteristics exhibited by these lesions. Discrimination between ovarian and non-ovarian lesions is of paramount importance, given the existence of marked discrepancies in both prognosis and management. If the lesion is of ovarian origin, the O-RADS MRI risk stratification system should be implemented in order to ascertain the risk of malignancy.