Ultrasonographic anatomy and physiology of the fetal kidney.

The aim of this work was to demonstrate the impact of ultrasonography in utero to gain a better understanding of the anatomy, growth, anatomical variations and function of the fetal kidney and urinary tract. Three main topics are discussed in this paper based on the authors' personal experience and data from the literature: 1) the technique of ultrasonography in utero, including the main difficulties encountered and limitations of this technique; 2) ultrasonographic study of the morphology, growth and anatomical variations of the fetal kidney. The length of the fetal kidney was found to be the most significant parameter for assessment of its growth. At term, the kidney measures slightly more than 4 cm in length, while the renal pelvis is usually no more than 10 mm thick; 3) current knowledge of the physiology of the fetal urinary apparatus especially the kidney. Excretory function of the kidney begins in the third month of gestation and its main role involves the regulation of the amniotic fluid.