Introduction
During embryogenesis, interference with the normal development of the Müllerian ducts of the female reproductive tract can lead to congenital malformations known as Müllerian anomalies. These abnormalities affect approximately 5-7% of women and may lead to a wide range of gynecologic and reproductive complications, including amenorrhea and infertility.
Further, adolescents may experience obstruction with concomitant pain after menarche due to retained menstrual blood caused by these malformations. Obstructive abnormalities can also lead to endometriosis due to retrograde menstruation. These anomalies are notably associated with renal pathologies as well. Diagnosing the broad spectrum of Müllerian anomalies accurately is crucial to ensure appropriate treatments are being chosen and reproductive outcomes are
optimized. Imaging is the primary method by which these anomalies are evaluated. Modalities such as magnetic resonance imaging (MRI) and ultrasound enable radiologists to differentiate various cervical, uterine, and vaginal abnormalities.
Background/Clinical Context
Embryology of Müllerian Anomalies
During the development of the fetus, paired Müllerian ducts give rise to the uterus, cervix, fallopian tubes, and upper two-thirds of the vagina. Three events are required for typical development to occur: duct formation, midline fusion, and resorption of the intervening septum.
Disruption of any stage of this process can result in a congenital Müllerian anomaly. These anomalies are further classified as specific developmental anomalies based on which event was affected. For instance, Müllerian agenesis or unicornuate uterus occur due to failure of duct development. Problems with fusion result in pathologies like uterine didelphys and bicornuate uterus. Finally, the most common anomaly, septate uterus, is caused by failure of septal resorption.
Current Imaging Approaches
Multiple imaging modalities can be used to diagnose Müllerian anomalies. Ultrasound is commonly the first-line imaging modality due to its ubiquitous nature and low cost. Of note, three-dimensional ultrasound is desirable for high-resolution visualization of uterine morphology, namely the contour of the uterus and internal indentation of the cavity. MRI is
particularly valuable due to its superior soft tissue contrast and multiplanar imaging capabilities including evaluation of structures beyond the uterus. In the setting of infertility evaluation, hysterosalpingography (HSG) is beneficial, as it can elucidate uterine cavity morphology and tubal patency.
Clinical Implications
The correct identification and diagnosis of Müllerian anomalies through imaging is paramount to optimal patient care. Adolescents experiencing cyclic pelvic pain and primary amenorrhea can benefit from early detection of obstructive pathologies to prevent complications such as endometriosis. Discovering and correctly identifying uterine anomalies in women of reproductive age influences fertility planning and ensures that the correct treatment is selected. Further, preoperative planning relies heavily on accounting for any malformations that may interfere with the usual surgical procedure. Taking these factors into account minimizes the risk of interference with surrounding structures and postoperative complications. Identification of both kidneys is paramount when assessing a patient with a Müllerian anomaly as these pathologies often coexist.
MRI also offers the advantage of evaluation of structures beyond the uterus, allowing for a comprehensive assessment of the female reproductive tract and ensuring that associated abnormalities are identified when evaluating a Müllerian anomaly.
Key Evidence/ Recent Advances
AFS Guidelines
The most widely used classification system for Müllerian anomalies is the American Fertility Society (AFS) guidelines established in 1988. This system is notable for its strong correlation with pregnancy outcomes in addition to its simplicity and recognizability. A downside is that it focuses on uterine abnormalities without allowing for complete analysis of the vagina and cervix. This may lead to insufficient classification of complex pathologies. In 2021, the American Society for Reproductive Medicine presented an updated Müllerian anomaly classification which expanded the previous guidelines and includes all categories of anomalies.
MRI and 3D Ultrasound
The main imaging modalities used to evaluate Müllerian anomalies are MRI and three-dimensional ultrasound (3D-US). One study demonstrated greater diagnostic accuracy of MRI (AUC 0.92) compared with 3D-US (AUC 0.88). MRI remains the main imaging modality for evaluation of complex female reproductive tract anomalies. The combined use of MRI and 3D-US may provide optimal diagnostic accuracy and treatment outcomes.
Key Takeaways
- Approximately 5-7% of women are affected by Müllerian anomalies, experiencing pathologies like primary amenorrhea, miscarriage, and pelvic pain.
- 3D transvaginal ultrasound and MRI are the optimal imaging modalities to diagnose and classify Müllerian anomalies.
- Endometriosis and renal abnormalities should be considered when evaluating a patient with a Müllerian anomaly.
Conclusion
The failure of any step in the normal development of the female reproductive tract can lead to deficits known as Müllerian anomalies, greatly impacting reproductive function and overall quality of life. The accuracy of diagnosis and classification of these anomalies has recently improved due to the evolution of imaging modalities such as MRI and ultrasound. The current ASRM classification system provides a straightforward, practical approach in this process. Radiologists will continue to play a crucial role in the efficient diagnosis and treatment of these anomalies as imaging technology continues to advance.
References
1. Pfeifer S et al. ASRM müllerian anomalies classification 2021 Fertility and Sterility, 116, 1238-1252
2. Ramakrishnan KK, Jerosha S, Subramonian SG, Murugappan M, Natarajan P. Comparing the Diagnostic Efficacy of 3D Ultrasound and MRI in the Classification of Müllerian Anomalies. Cureus. 2024 Oct 1;16(10):e70632. doi: 10.7759/cureus.70632. PMID: 39483598; PMCID: PMC11526810.
3. Singh et al. Müllerian Anomalies: Revisited Journal of Gastrointestinal and Abdominal Radiology 2026; 09(01): 003-017 DOI: 10.1055/s-0045-1811972
