Fetal renal volume assessment by three-dimensional ultrasonography

OBJECTIVE: This study was undertaken to measure fetal renal volume by means of three-dimensional ultrasonography and to use those data to establish th e accurate constant and formula for fetal renal volume assessment with two- dimensional ultrasonography. STUDY DESIGN: Singleton fetuses between 15 and 40 weeks' gestation were inc luded. The volumes of both fetal kidneys were measured with three-dimension al ultrasonography. Three fetal renal diameters (largest anteroposterior, t ransverse, and longitudinal diameters) were measured, and the constant of t he fetal renal volume formula was calculated. Linear regression curves were made for each kidney from the fetal renal volume, the three diameters, and the constant. RESULTS: A total of 112 fetuses were included. The following fetal renal vo lume formula was established: Fetal renal volume = Constant (R) x Largest a nteroposterior diameter (x) x Largest transverse diameter (y) x Largest lon gitudinal diameter (z). The volumes, the three diameters, and the constants appeared different between the right and left kidneys but not statisticall y significantly so. CONCLUSION: Three-dimensional ultrasonography is useful in assessing fetal renal volume. The fetal renal volume formula makes possible accurate measur ements of fetal renal volume by two-dimensional ultrasonography.