Situs anomalies on prenatal MRI

Area of Science:

• Medical Imaging
• Fetal Medicine
• Developmental Biology

Background:

• Situs anomalies represent abnormal organ arrangement, often linked to severe developmental errors.
• Prenatal ultrasonography (US) is a primary tool, but its visualization capabilities for situs anomalies can be limited.

Purpose of the Study:

• To demonstrate the in utero visualization of fetal situs anomalies using prenatal magnetic resonance imaging (MRI).
• To compare the diagnostic performance of MRI against US for detecting situs anomalies.

Main Methods:

• A retrospective analysis of 12 fetuses diagnosed with situs anomalies via prenatal MRI.
• Standard MRI protocol assessed the entire fetus, focusing on heart, venous drainage, aorta, gastrointestinal tract, liver, gallbladder, and spleen.
• Prenatal US served as the comparative imaging modality.

Main Results:

• Various situs anomalies were identified, including situs inversus totalis, situs inversus abdominis, and situs ambiguous with polysplenia/asplenia.
• Congenital heart defects (CHDs), vascular anomalies, and intestinal malrotations were common associated malformations.
• MRI provided additional diagnostic findings in 7/12 cases compared to US, though fetal CHD visualization was limited.

Conclusions:

• Prenatal MRI can visualize fetal situs anomalies and associated malformations, providing crucial information for perinatal care.
• A standardized MRI protocol can reveal additional details beyond US, aiding in the confirmation and specification of situs anomalies.
• While effective for situs anomalies, MRI has limitations in fully visualizing fetal CHDs.