The natural history of congenital lower urinary tract obstruction (LUTO) is highly variable and dependent on the gender, severity, duration, and age of onset of the obstruction. Outcome is measured in terms of postnatal survival and is dependent on two factors: pulmonary development and renal function. Complete urethral obstruction or significant restriction of urethral flow results in accumulation of urine within the fetal bladder, leading to marked distention. Prolonged obstruction results in smooth muscle hypertrophy and hyperplasia within the bladder wall, and eventual impairment of contractile capacity as well as compliance and elasticity. Histological studies indicate a progressive dilatation of the distal to proximal renal tubules associated with development of peritubular and interstitial fibrosis. Component of the prenatal evaluation is the serial analysis of fetal urine, obtained by vesicocentesis. More recent studies were designed to focus on the long-term outcomes of children with specific documented urethral obstructions.