Mullerian anomalies: revisiting imaging and classification

Mullerian duct anomalies (MDA) are a group of uncommon but treatable causes of infertility and pregnancy complications. This review describes the embryology, American Society of Reproductive Medicine (ASRM) classification 2021, and corresponding imaging features of MDA. The three phases of embryological development of Mullerian duct structures are described. The main emphasis is on the ASRM 2021 classification of MDA into nine descriptive categories, while the European Society of Human Reproduction and Embryology and the European Society for Gynecologic Endoscopy (ESHRE/ESGE) classification is also briefly described where necessary. MRI imaging features of MDA along with the acquisition techniques are discussed in detail, as MRI is the ideal imaging modality for MDA diagnosis. In addition, the current role of imaging modalities such as hysterosalpingography and ultrasound including 3D transvaginal ultrasound is also elucidated. The review aims to revisit the MRI imaging features of Mullerian anomalies and reiterates that an accurate description of each anomaly and precise communication with clinicians is the priority rather than rigidly fitting the anomaly into one particular category. CRITICAL RELEVANCE STATEMENT: The ASRM 2021 classification of Mullerian anomalies has re-defined the criteria for an arcuate uterus. Radiologists must know of the new classification and imaging features and try to describe each anomaly accurately rather than forcefully fitting an anomaly into a definite category. KEY POINTS: MDA has an important role in infertility and pregnancy complications. Knowledge of imaging features helps radiologists aid patient management; MRI is the preferred imaging modality for MDAs. An accurate MRI-based description of Mullerian anomalies is crucial, avoiding the pitfalls of rigid categorization.