Congenital cystic renal diseases may become clinically apparent in the fetus, child, or adult. Congenital cystic renal diseases that can be diagnosed by antenatal ultrasound examination will be reviewed here. The diagnosis, clinical manifestations, and prognosis of renal cysts and cystic disorders in children and adults are discussed separately. (See "Renal cystic diseases in children" and "Diagnosis of and screening for autosomal dominant polycystic kidney disease" and "Genetics and pathogenesis of nephronophthisis" and "Autosomal dominant interstitial kidney disease (medullary cystic kidney disease)", section on 'Mucin 1 mutations'.)
ULTRASOUND APPEARANCE OF THE KIDNEY
The normal renal cortex is as echogenic as the liver or spleen, while the medulla is relatively hypoechogenic. By definition, a hyperechogenic kidney has a renal cortex more echogenic than the liver and spleen. It is important to note that normal fetal kidneys can be physiologically hyperechogenic in the first and second trimester.
Ultrasound examination of fetuses with hyperechoic kidneys includes assessment of :
- Amniotic fluid volume
- Kidney size
- Corticomedullary differentiation
- Level of renal echogenicity
- Location and size of renal cysts (if present)
Corticomedullary differentiation can be absent or present and, if present, is further classified as normal, increased, or reversed . Normal corticomedullary differentiation is defined according to the echogenicity of the cortex and medulla. The combination of renal cortex as echogenic as liver or spleen and relatively hypoechogenic medulla is characteristic of well-defined, normal corticomedullary differentiation.