What a bicornuate uterus looks like on ultrasound
A bicornuate uterus is a congenital uterine shape where the upper uterus (fundus) is indented, creating a heart-like轮廓 on imaging. On ultrasound, this appears as two horns separated at the top with a wider base below. Transvaginal ultrasound is often the first step; saline infusion sonohysterography can outline the cavity, while MRI best defines external fundal indentation and confirms the diagnosis. Accurate imaging is essential because a bicornuate uterus differs from a septate uterus and is associated with particular obstetric outcomes. Understanding the pattern seen on ultrasound guides further testing, counseling, and, when needed, surgical or obstetric management.
Typical ultrasound features of a bicornuate uterus
Ultrasound features reflect the outward indentation of the fundus and the two symmetrical cavities. Key signs on imaging help distinguish a bicornuate uterus from other Müllerian anomalies and guide next steps.
Two symmetric cavities with an external fundal cleft
Each uterine horn is seen in the upper corners of the pelvis, and the fundal indentation is visible on the outer contour of the uterus as a dip or cleft. MRI is the standard for confirming this external indentation and measuring its depth.
Transvaginal and saline infusion sonohysterography findings
Transvaginal ultrasound shows the indentation at the top; sonohysterography fills the cavity with saline to reveal two separate horns and the shape of the inner lining. The cavity does not have a longitudinal septum dividing it from inside, which helps separate bicornuate from septate uterus.
Size, wall thickness, and cervical findings
Uterine size and cavity dimensions vary; the cervix is usually normal, and a single cervix is present. The fallopian tubes are typically normal in position and structure. Absence of a vagina or renal anomalies should prompt a broader evaluation of Müllerian derivatives.
How it forms and related anatomy
During embryonic development, incomplete fusion of the Müllerian ducts results in a bicornuate uterus. The degree of fusion failure determines the appearance and obstetric implications. Accurate classification influences counseling and management.
Embryology in brief
- Müllerian ducts fuse, and the lower portions canalize to form the uterine cavity and cervix.
- Incomplete fusion at the top produces a heart-shaped uterus with two horns.
- Absorption of the septum between ducts typically completes by midgestation; in bicornuate, the septum is absent inside, but an external indentation remains.
Key anatomical distinctions
- Bicornuate vs septate: external indentation present in bicornuate; internal septum present in septate.
- Unicornuate: only one developed horn, often with a single fallopian tube.
- Didelphys: complete duplication of cervix and sometimes vagina, with two separate uterine bodies.
Pregnancy risks and outcomes
A bicornuate uterus can increase certain pregnancy risks compared with a typical uterine shape. Early ultrasound assessment and close monitoring can improve outcomes, although many people with a bicornuate uterus have successful pregnancies.
Common obstetric considerations
- Miscarriage risk may be moderately elevated, especially in the second trimester.
- Preterm birth and breech presentation are more common.
- Fetal growth restriction and placenta-related issues can occur, warranting surveillance.
Role of imaging and specialist care
Early obstetric ultrasound and, when indicated, MRI define the anatomy and guide planning. Consultation with maternal–fetal medicine or reproductive surgery can help tailor prenatal care and delivery planning.
Diagnostic pathway and imaging comparison
A stepwise approach to imaging improves accuracy and avoids unnecessary procedures. Ultrasound is usually first; MRI adds detail when the diagnosis is uncertain or surgical planning is considered.
| Attribute | Verified Detail | Source Type |
|---|---|---|
| First-line imaging | Transvaginal ultrasound with saline infusion sonohysterography | Clinical guideline consensus |
| Best for external fundal contour | MRI | Imaging literature and expert review |
| Key distinguishing feature vs septate | External fundal cleft with no internal septum on MRI | Imaging studies |
| Cavity assessment | Sonohysterography or MRI to outline the two horns | Imaging literature |
| Associated anomalies | Renal ultrasound when indicated due to Müllerian–renal association | Clinical practice guidance |
When to consider further evaluation or surgery
Not all bicornuate uteri require intervention; management focuses on symptoms and obstetric history. Surgical options are considered when pregnancy loss or preterm birth recurs and imaging confirms a significant external contour abnormality.Surgical repair (metroplasty) is individualized and typically offered after thorough imaging review and specialist consultation. Postoperative outcomes and future pregnancy planning depend on the extent of resection and uterine function.
Key points to remember
- Ultrasound often shows two horns with a fundal cleft; MRI confirms external indentation.
- A single cervix and normal tubes are typical; distinguish from septate, unicornuate, and didelphys anatomy.
- Pregnancy risks include miscarriage and preterm birth; early and coordinated care can improve outcomes.
- Use a stepwise imaging approach: ultrasound first, MRI when clarification or surgical planning is needed.
- Management is individualized; consult subspecialists when recurrent loss or compelling symptoms are present.