Evaluation of normal and abnormal fetal renal microvascular flow characteristics of three-dimensional MV-flow imaging

To evaluate the applicability of three-dimensional MV-Flow imaging for prenatal renal diagnosis.

This prospective study included normal and abnormal kidneys ranging from 20 to 40 weeks gestation between April and July 2023. All participants underwent conventional ultrasound and three-dimensional MV-Flow examinations. The renal volume and microvascular indexes were obtained by the three-dimensional MV-Flow.

A total of 207 normal kidneys from 154 fetuses and 67 abnormal kidneys from 53 fetuses, with conditions such as renal cystic diseases, hyperechoic kidney, large kidney, and small kidney were included. Normal renal volume, vascularization index, and vascularization-flow index increased slightly with gestational age (p < 0.001). No correlation was found between gestational age and flow index (p = 0.604). The microvascular indexes decreased in the fetal renal cystic disease group while renal volume increased. Higher vascularization index and vascularization-flow index were observed in the hyperechoic kidney group. The microvascular indexes of the large and small kidney groups were within the reference range for normal kidneys. Only the autosomal dominant polycystic kidney disease exhibited an absence of distinct subcapsular microvascular flow in the MV-Flow image, referred to as the "thick shell sign".

Fetal renal volume, vascularization index, and vascularization-flow index increase with gestational age. Quantitative evaluation using 3D MV-Flow imaging reveals varying renal volume and microvascular perfusion characteristics among different fetal renal abnormalities.