In fact, we have repeatedly explained to each parent before the surgery, but some of them don’t remember, and some parents even ask the doctor if there is something wrong with the surgery. The kidney and renal pelvis are dilated due to urinary obstruction, and the ultrasound indicates “hydronephrosis”. The prolonged dilatation makes it difficult to restore the elasticity of the “ball” of the kidney to the state when there is no hydronephrosis, and the purpose of surgery is to remove the obstruction and drain the urine without resistance to prevent further damage to the kidney function. The purpose of surgery is to remove the obstruction, drain the urine without resistance, and avoid further damage to kidney function. The purpose of the surgery is to relieve the obstruction and drain the urine without resistance to prevent further damage to the kidney function, not to “drain” as most parents think, so there is no need to make a fuss if the fluid still exists after the surgery. Because there are many factors that affect the ultrasound results that lead to large errors, sometimes a CT or renal nuclear scan is needed to confirm the changes in kidney function. Another point to note is that some parents are afraid of the trouble of having ultrasound done in their local area, because it is impossible for every ultrasound doctor to have such a good knowledge of the regression of hydronephrosis and postoperative imaging, and often some ultrasound doctors mislead patients and families. However, this requires ultrasound doctors to check the cortical condition of each part of the kidney very carefully and patiently, in addition to the patient cooperation of parents and children during the examination, which tests not only the level of doctors but also the patience of parents, which is really not that easy to do. Finally, renal nuclear scan is an objective test to evaluate the function of both kidneys, which can directly assess the function of both kidneys and is an important reference for the review of hydronephrosis.