The most likely cause of hydronephrosis in children is congenital abnormalities, which means that the kidneys and ureters have abnormal structures and become tortuous, so that the kidneys do not discharge urine smoothly and gather in the kidneys or ureters, which requires active treatment and urology or pediatric surgery to remove the obstruction. The majority of hydrocele in children is caused by this, and it is necessary to remove the congenital abnormality so that the kidneys can discharge urine smoothly. If the obstruction is not removed for a long time, the kidney will be damaged and the glomerular filtration pressure will be reduced or even disappeared, thus losing the filtration function, which means that the kidney will completely lose the function of detoxification and drainage of water, so children need active treatment whenever hydrocele occurs.