Inclusion Criteria:  Boys and girls > 5 years with bladder exstrophy or isolated epispadias; sphincteric incontinence (leak point pressure < 45 cm d'H20, open bladder neck during filling, stress urinary incontinence); normal renal function (eGFR > 90ml/min); no (or stable) upper urinary tract dilatation in ultrasound.  Exclusion Criteria:  under 5 years or more than 18 years old; renal insufficiency (acute or chronic); evolutive deterioration of the upper urinary tract (hydronephrosis); unmanageable detrusor instability; residual volume greater than 100 ml after voiding; bleeding disorders.