From the Guidelines
When a bicornuate uterus is identified on ultrasound, MRI would typically reveal a single uterine fundus with partial indentation, two distinct endometrial cavities, and a single cervix, with an indentation depth greater than 1 cm at the fundus, as supported by the ACR Appropriateness Criteria for female infertility 1.
Key Findings on MRI
- A single uterine fundus with partial indentation
- Two distinct endometrial cavities
- A single cervix
- External contour of the uterus shows a heart-shaped appearance with an indentation depth greater than 1 cm at the fundus
- Normal zonal anatomy with preserved myometrium between the two cavities
- Uterine horns separated by myometrial tissue rather than a complete septum
Additional Evaluation
MRI can also better characterize the external fundal cleft, which typically has an angle of less than 105 degrees, and provide superior soft tissue contrast compared to ultrasound, allowing for clear differentiation between a bicornuate uterus and other Müllerian duct anomalies, such as septate uterus, as noted in the study by 1. Additionally, MRI can simultaneously evaluate for associated renal anomalies, which occur in approximately 30% of patients with bicornuate uterus due to the embryological link between urinary and reproductive system development. The high accuracy of MRI in detecting uterine abnormalities, including bicornuate uterus, adenomyosis, and leiomyomas, makes it a valuable tool in the evaluation of female infertility, as demonstrated by the study 1.
From the Research
MRI Findings in Bicornuate Uterus
When a bicornuate uterus is identified on ultrasound, additional findings on MRI may include:
- Two symmetric uterine cavities that are fused caudally and have some degree of communication between them, usually at the uterine isthmus 2
- A separatory cleft of tissue that extends to the internal os in complete bicornuate uterus 2
- Variable degree of septation of the two uterine horns, with partial bicornuate uterus having a lesser degree of septation 2
- Accurate classification of the type of uterine anomaly, with MRI correctly identifying and classifying the anomaly in most cases 3
- Detection of associated anomalies, such as a double cervix and septate vagina, which can be diagnosed with MRI 4
Diagnostic Accuracy of MRI
MRI has been shown to be a valuable tool for the diagnosis of uterine anomalies, including bicornuate uterus, with a high degree of accuracy:
- MRI correctly identified and accurately classified the type of anomaly in 6 out of 8 cases in one study 3
- MRI diagnosis was correct in 24 out of 31 patients in another study, although there were some false-positive diagnoses of bicornuate uterus 5
- Transvaginal 3-D ultrasonography may be more accurate than MRI for the diagnosis and classification of congenital uterine anomalies, but MRI is still a useful diagnostic tool 5