Congenital anomalies of the kidney and urinary tract (CAKUT) constitute approximately 20 to 30 percent of all anomalies identified in the prenatal period . Defects can be bilateral or unilateral, and different defects often coexist in an individual child.
An overview of the congenital anomalies of the kidney and urinary tract (CAKUT) is presented here. The antenatal screening and postnatal evaluation of infants with CAKUT are discussed in greater detail separately. (See "Evaluation of congenital anomalies of the kidney and urinary tract (CAKUT)" and "Congenital ureteropelvic junction obstruction" and "Primary megaureter in infants and children" and "Ectopic ureter" and "Renal ectopic and fusion anomalies" and "Autosomal recessive polycystic kidney disease in children".)
ASSOCIATION WITH END-STAGE RENAL DISEASE (ESRD)
Because CAKUT play a causative role in 30 to 50 percent of cases of end-stage renal disease (ESRD) in children , it is important to diagnose these anomalies and initiate therapy to minimize renal damage, prevent or delay the onset of ESRD, and provide supportive care to avoid complications of ESRD. Patients with malformations with a reduction in kidney numbers or size are most likely to have a poor renal prognosis . (See 'Renal development and CAKUT' below and "Overview of the management of chronic kidney disease in children".)
Normal embryology — Normal embryologic development of the kidney occurs in three stages (figure 1):
- Pronephros – Transient rudimentary and nonfunctioning system that begins in the fourth week of gestation (ie, day 22) and disappears by end of the fourth week (ie, day 28). Degeneration of the pronephros is required for normal kidney development.
- Mesonephros – Derived from the intermediate mesoderm by day 26 and by the fifth week develops into 20 paired tubules that produce small amounts of urine. The mesonephros ultimately fuses with the cloaca and contributes to the formation of the urinary bladder, and in the male, the genital system is derived from the mesonephric ducts and some tubules.
- Metanephros – The metanephros, which is composed of the metanephric mesenchyme and ureteric bud epithelium (caudal portion of the mesonephric duct), is the last stage of renal development and forms the permanent kidney beginning at the fifth week of gestation.