Three-dimensional ultrasonography of the fetal distal lower extremity: normal and abnormal

The objective of this study was to compare two-dimensional and three-dimensional ultrasonographic evaluation of fetal distal lower extremities. Data from two-dimensional and three-dimensional ultrasonographic examinations from 40 distal lower extremities in 33 fetuses from a predominantly high-risk patient population were compared. Three-dimensional ultrasonography routinely provided three orthogonal planes (coronal, sagittal, and axial) for distal lower extremity evaluation. Specific features of distal lower extremity evaluation were not different using two-dimensional and three-dimensional ultrasonography. Rotation of the rendered volume provided assistance in assessing all but one of 40 distal lower extremities. Time from image acquisition to assessment for two views (coronal and sagittal) was longer with three-dimensional ultrasonography (8.2 min) than with two-dimensional ultrasonography (3.2 min). Confidence in the diagnosis of abnormal distal lower extremities was slightly improved using three-dimensional ultrasonography compared to two-dimensional ultrasonography. Pregnancy management was assisted in three of the four cases with isolated limb anomalies. In conclusion, three-dimensional ultrasonography improves the ability to evaluate the fetal distal lower extremity because of the multiplanar nature of volume assessment and the ability to rotate volume data sets. In addition, it provides assistance in counseling families, particularly for cases involving isolated limb anomalies.