Patient Li**, male, 5 years old and 1 month old, was treated with bone marrow transplantation at Southern Hospital for thalassemia major. Preoperative ultrasonography revealed obstruction of the left renal pelvic ureteral junction and moderate hydronephrosis in the left kidney. After admission, IVP examination revealed obstruction of the left pelvic ureteral junction and moderate hydronephrosis in the left kidney, with delayed visualization of the left kidney. The patient had long-term anemia, poor development, small posterior abdominal space, and a history of splenectomy, which made the operation difficult. After discussion in our department, we decided to perform posterior laparoscopic dissection left renal pyeloplasty with pediatric laparoscopic equipment, and the operation was performed by Dr. Caiyong Lai, deputy chief surgeon. Intraoperatively, the left renal pelvis was significantly dilated and the ureteral junction of the renal pelvis was narrowed (Figure), and the stenotic segment and dilated pelvis were excised and reanastomosed. Under the laparoscope, the anatomical level was clearly displayed, and after nearly two hours of delicate operation, the operation was successfully performed. As the intraoperative bleeding was about 10 ml, only three small holes were used for the operation, and the child recovered well after the operation. Ureteropelvic junction obstruction (UPJO) is a common cause of hydronephrosis in children and adolescents, mostly congenital, mostly on the left side, and patients mainly present with pain, hematuria or infection, and infants may present with abdominal masses. Preoperative urography, nephrography and CT examination can clarify the diagnosis. Treatment is mainly surgical. There are four commonly used surgical procedures, which are selected according to the type and degree of stenosis, among which dissection pyeloplasty has the most definite effect. Previously, open surgery was highly invasive, with little room for intraoperative manipulation and significant postoperative scarring. Laparoscopic left pyeloplasty is now the ideal method for the treatment of this disease. Figure: Laparoscopic view clearly shows a significantly dilated left renal pelvis (due to instrumentation) and stenosis of the ureteral junction of the renal pelvis.