Separation of the renal pelvis in children is not uncommon in clinical practice, and the causes of this condition include urine holding, congenital ureteral stenosis, and urinary tract infections. 1. Holding back urine: Usually there is no timely urination, and the renal pelvis will be separated during the examination, and the corresponding condition shows that the degree of separation is mostly less than 10 millimeters. 2. Congenital ureteral stenosis: localized ureteral stenosis will also cause hydronephrosis in the renal pelvis and ureter above the stenosis area, which will further lead to separation of the renal pelvis, and most of them are more than 10 mm. 3. Urinary system infection: urinary system infection caused by various reasons will cause local adhesion, affecting urine drainage, resulting in renal pelvis separation, usually accompanied by frequent urination, urinary urgency, urinary pain and fever and other symptoms. If the separation of the renal pelvis is accompanied by obvious urinary abnormalities, it is necessary to consult a doctor for observation and standardized treatment under the guidance of the clinician after diagnosis of the condition, so as to avoid delays in the condition.