Renal Hypoplasia and Dysplasia

The human metanephros is the direct precursor of the mature kidney: It begins to form in the fifth gestational week, when ureteric bud branches from the mesonephric duct; thereafter, renal mesenchyme condenses around the advancing bud and forms nephrons while the bud itself forms the ureter and collecting ducts. Perturbation of these events underlies the spectrum of disorders called congenital anomalies of the kidney and urinary tract (CAKUT) (1,2). Approximately 40% of all children with chronic renal insufficiency or end-stage renal failure have CAKUT (3,4), and in approximately half of these, renal malformations are associated with lower tract obstruction that is caused by posterior urethral valves, a disease that is unique to boys.