Mild separation of the left renal pelvis may be related to causes such as kidney stones, ureteral malformations, and prostatic hyperplasia. It can usually be treated by drugs and surgery. 1. Kidney stone: the stone makes the urethra form obstruction, urine can not come out, leading to the renal pelvis become bigger and cause the separation of renal pelvis. It can be treated by extracorporeal shock wave lithotripsy, percutaneous nephrolithotomy and so on according to the specific conditions of patients. 2. Ureteral malformation: congenital developmental abnormality leads to ureteral malformation, which prevents urine from being discharged normally, thus leading to renal pelvis separation. It can be treated by surgical removal of the narrow section to ensure the patency of the ureter. 3. Prostatic hyperplasia: Hyperplasia of the prostate may compress the urethra and cause urine to accumulate in the renal pelvis, leading to separation of the renal pelvis. It can be treated with drugs such as finasteride and terazosin, and if necessary, it can also be treated by transurethral resection of the prostate. It is recommended that patients with renal pelvis separation go to the hospital in time, complete the relevant examinations under the guidance of the doctor, clarify the cause, and actively treat it, avoid self-medication.