The incidence of duplicated kidney and duplicated ureteral malformation is about 0.8%, which is one of the common congenital diseases of the pediatric urological system. Repetitive kidney and ureteral malformations can be unilateral or bilateral. There are more unilateral than bilateral cases, about four times more right than left, and more females than males. The diagnosis and treatment of duplicated renal malformation is important for early diagnosis, and delayed diagnosis or misdiagnosis may lead to irreversible damage to the function of the duplicated kidney. The cause of the disease is a small blind duct called a ureteral bud that protrudes dorsally from the end of the mesonephric duct (Wallflower’s duct) into the cloaca in the sixth week of embryonic life. The ureteral bud grows rapidly, and its tip is surrounded by primitive raw kidney tissue, resembling a fava bean. The ureteral bud develops into the renal pelvis, branches to form the calyces, and then branches to form the calyces and collecting ducts. If the branching is premature, a duplicated ureteral malformation is formed. The height and number of branches may determine the formation of complete or incomplete, double or multiple ureteral malformations. Duplicated ureters are often accompanied by duplicated kidneys. Complete duplicated ureteral malformation in pediatric patients can have clinical symptoms in the neonatal and infantile stages, but because of the atypical clinical symptoms, it is very easy to misdiagnose, and the diagnosis and treatment are often delayed for months to years. The main manifestations are as follows: 1. Incomplete duplicate ureteral malformation or complete duplicate ureteral malformation, where the ureter opens in the bladder and there are no comorbidities. These cases have no clinical symptoms at all and are only detected when a comprehensive urological examination is performed. 2. Duplicate kidneys with comorbidities and symptoms such as pyelitis, kidney stones, tuberculosis, tumors, and fluid retention are detected only when a full urinary system examination is performed. 3. Complete double ureteral malformation in which the ureter opens in the vulvar vestibule, vagina, etc. It causes the patient to have a history of urine loss since early childhood, wetting the bed at night and often not drying the underwear during the day; however, the patient also has normal urinary activity. On examination of the vulva, abnormal ureteral openings were seen. Even if the abnormal ureteral opening is not found, intravenous pyelogram can often confirm this congenital malformation. Diagnostic methods: 1. Intravenous pyelogram: The lower renal pelvis is similar to the normal pelvis, but the number of calyces is reduced and the position is low. The upper renal pelvis is mostly atrophied and small or cystic in shape. In addition, hydronephrosis may be present. There are various types of this malformation, and their x-ray presentation is as follows. (1) A duplicated renal pelvis with a single ureter. (2) Duplication of the renal pelvis and part of the ureter. (3) Duplication of the renal pelvis and all of the ureter, which may be accompanied by an ectopic ureteral opening or a blind pocket at one end. ④A single renal pelvis but a duplicated ureter, and one end of the duplicated ureter may be a blind pouch. 2, ultrasound performance: generally only repeat kidney can be shown, in addition to the growth of the kidney length diameter, strong echogenic collection system light point group is clearly divided into two groups. However, unless the duplicated ureter is combined with fluid expansion, the ultrasound display is not clear. 3, CT performance: One kidney has two sets of pelvic ureteral system, and the upper pelvis is often dysplastic and inwardly oriented. The inferior pelvis is normally developed with large and small calyces, and its position is low and outward. Repeated kidney with dilated ureteral effusion in the upper pelvis is commonly associated with ectopic ureteral opening. Tracing the scan to the pelvis reveals a full-length dilated draining ureter in the upper pelvis, with the lower end not entering the bladder. However, CT cannot clearly specify the location of the opening. 4, MR performance: coronal position can more clearly show the duplicated ureteral malformation of the renal pelvis. In addition to the duplicated kidney being longer than normal, when the upper kidney segment is cystically dilated due to water retention, its dilated draining ureteral segment can also be partially shown, and the lower kidney segment can be seen to be displaced outward by the compression of the hydronephrosis pelvis. Treatment modality: 1. No complications or asymptomatic without treatment. 2, Ureteral opening ectopic, with urinary incontinence, if the kidney function is still good then do ureteral bladder reimplantation. 3.If the duplicated kidney is complicated with stone, tuberculosis or hydronephrosis infection, kidney function damage, or ureteral ectopic opening for surgical treatment, different ways of surgical treatment should be taken for the etiology and function of each part of the duplicated kidney and the lesion. Traditional surgical methods include duplicate nephrectomy and duplicate ureterectomy. In recent years, laparoscopic techniques have gradually become the routine surgical procedure for cases of duplicated renal malformation requiring upper hemipelvectomy. Combined with larger cysts at the end of the ureter, laparoscopic ureteral end cyst removal or ureteral bladder reimplantation with pneumatic bladder is easily feasible.