Posterior urethral valves, in infants and neonates, are the most common urethral obstructive disease. The flap is usually located at the distal end of the prostatic urethra and is formed by mucosal folds that resemble a very thin membrane. When urinating, the valve can cause varying degrees of obstruction, what is the cause of urethral valve? The main harm caused by posterior urethral valve disease causing lower urinary tract obstruction in the fetal period is that the development of the original kidney tissue in a high pressure environment in the lumen will inevitably lead to abnormalities in the development of the urinary tract, including damage to the structure and function of the bladder, ureteral smooth muscle and renal parenchyma. 1, bladder dysfunction about 25% of children with posterior urethral valve disease have varying degrees of bladder function abnormalities, mostly manifested as urinary incontinence. In the past, it was thought to be related to sphincter disorders (abnormal development of the membranous urethra and bladder neck due to the valve being located at the level of the sphincter). 2. Vesicoureteral reflux is one of the common complications of posterior urethral valve disease, with 1/3 to 1/2 of the children having combined vesicoureteral reflux at the time of the initial diagnosis of the disorder. Most of these are secondary to increased intravesical pressure, ureteral diverticulum and loss of function of the vesicoureteral junction. 3, hydronephrosis in cases with significant urethral obstruction and ureteral dilatation of varying degrees, after endoscopic removal of the posterior urethral valve or cystostomy, the hydronephrosis will gradually decrease once the obstruction is lifted. If the hydronephrosis does not diminish, it is important to think about the presence of obstruction at the ureteral-vesical junction, the inability of the ureteral dynamic obstruction to produce effective peristalsis, and whether the hydronephrosis is secondary to increased intravesical pressure or increased urinary flow, factors that will have different effects in different cases. It has been pointed out that after posterior urethral valvotomy, ureteral diameter reduction and relief of hydronephrosis will take several years, and it is suggested that further surgical treatment of ureter can be suspended for consideration when renal function is stable and urinary tract infection can be controlled. 4. Effects on renal function Due to the effects of ureteral hypertension, almost half of the children have significant urinary concentration dysfunction. The aim of treatment for posterior urethral valve disease is to preserve renal function to the maximum extent possible. In the early years of recognition of posterior urethral valve disease (30 years ago) approximately 25% of children died within 1 year of age, 25% died in childhood, and approximately 50% survived into young adulthood with varying degrees of combined renal dysfunction. Nowadays, neonatal deaths due to renal dysfunction and sepsis are rare, and most of these deaths in the neonatal period are due to respiratory failure due to combined pulmonary dysplasia. However, children with posterior urethral valve disease may be born with severe renal dysfunction, and even after release of the obstruction, infection due to urinary retention or reflux may develop due to impaired renal function combined with hypertension. The renal dysfunction may be the result of parenchymal dysplasia, hydronephrosis, infected renal atrophy or possibly progressive glomerulosclerosis due to renal hyperfiltration. As a result of urethral obstruction due to posterior urethral valve disease, increased ureteral pressure first affects the most distal renal units, and in some children urinary concentration is more impaired than glomerular filtration rate, leading to increased urine flow and severe dehydration and electrolyte balance imbalance.