Duplicative kidneys (duplicative kideny), refers to the normal renal region has two kidneys, two sets of collecting system, referred to as duplicative kidneys, especially refers to the extra development of the kidney (upper kidney). Clinically, duplicative kidneys are more common at the age of 2-5 years, more common in girls than in boys, more common on the left side than on the right side, and bilateral kidneys account for about 5% of the cases. Etiology and embryo] In the fourth week of the embryo, the lower end of the mesonephric duct curves toward the cloaca and protrudes a small blind tube toward the back, called the ureteric bud, which grows rapidly, the proximal end of which will form the ureter, and the distal end of which will be embedded by the renal tissue mass, which resembles the shape of a fava bean, and develops into the renal pelvis, the calyces, and the collecting ducts, and in the course of which, if the distal end of the ureteric bud branches out into two, then it will form a duplicated renal pelvis. If the branching is too early, an incomplete double ureter is formed. In the process of development, if another ureteral bud emanates from the lower end of the mesonephric duct and rises side by side with the normal ureter, a complete double ureteral malformation occurs. And the distal primitive renal tissue mass forms two kidneys. [Pathology] The duplicated kidneys appear as one and are co-located within a single renal peritoneum. There are three types of duplicated kidney pathologic morphology: type A is developmental; type B is hydronephrosis, resembling the alteration of pediatric hydronephrosis, with much obstruction below, often combined with ureteral cysts; and type C is dysplasia, which is often combined with ectopic ureteral openings. The two ureters of the duplicated kidney are in the same sheath, and the innervating vessel is one, and occasionally the two ureters are not far downstream to converge into one, which is called Y-type ureter. The blood supply to both kidneys originates from a single renal hilum. The main blood vessel enters the lower kidney, fewer enter the upper kidney, and it is the second or third level branch, and it is rare that the blood vessel from the renal hilum directly enters the upper kidney. [Diagnosis] (A) Clinical manifestations 1, urinary tract infection: characterized by intermittent, recurrent urinary tract infections, for the heavy kidney urinary flow is not smooth, bacterial reproduction. 2.Urinary dribbling: caused by ectopic opening, the degree of urinary dribbling is directly proportional to the upper renal function, renal function is good, dribbling is heavy. This kind of urinary dribbling is characterized by normal urination and dribbling between two times of urination. Difficulty in urination: it is caused by the obstruction of the urethral opening caused by large ureteral cysts, and in a few cases, the cysts detached from the urethral opening can be seen in the examination of the perineum. 4, abdominal mass: heavy renal and ureteral effusion, to a certain extent, clinically palpable mass, mass in the lateral abdomen, cystic. (B) Laboratory examination 1, ultrasonography for the preferred method, in the renal area to see the two collecting system, that is, double renal pelvis image, the diagnosis can be confirmed. When the duplicated ureter is dilated and the diameter is larger than 37.5px, ultrasound can show its course, and the ureter goes down behind the bladder and does not enter the bladder, the diagnosis of ectopic opening should be thought of, and ultrasound can show it in most of the ureteral cysts. The above two images can be used as supporting evidence for the diagnosis of heavy kidney. 2.IVP can confirm the diagnosis if it shows double renal pelvis and double ureteral images, but this kind of image is not common and only accounts for about 1/4 of the cases, and most of the heavy kidneys do not show images. At this time, according to the lower renal imaging changes, it is helpful for the diagnosis of renal aggravation, the lower kidney: (1) the number of calyces is less than 3, and the renal pelvis is compressed; (2) the kidney is outwardly and downwardly displaced; (3) the kidney has a renal axial transposition; (4) the shadow of cysts can be seen in the bladder. Improve the diagnosis rate of heavy kidney. 3, nuclide examination SPECT examination is commonly used, it is highly sensitive. As long as the heavy kidney residual function of about 5%. Drugs can enter the heavy kidney, and the instrument can recognize the shape and size of the kidney. Treatment] According to the type of heavy kidney, decide the means of treatment, developmental heavy kidney does not need treatment, in the case of urinary tract infection, drugs can control. b, c two types of heavy kidney, often infections, drugs can not control, more use of surgical treatment, surgery will be heavy kidney, repeat ureter resection, surgery, pay attention to do not damage to the lower kidney and its ureter, to reduce the bleeding in the operation commonly used methods: (1) to find dominate the heavy kidney blood vessels, close to the kidney parenchyma cut off; (2) the heart of the heavy kidney, the kidney and its ureter, to reduce bleeding, to reduce bleeding. (1) Find the blood vessels governing the heavy kidney and cut them off close to the renal parenchyma; (2) Cut off the heavy kidney by auricular forceps to block the renal hilum; (3) Free the heavy kidney with gentle movements to reduce the tension on the renal hilum. Treatment of duplicated ureter: it should be free near the wall of duplicated ureter, leaving the blood flow to the lower renal ureter as much as possible, avoiding damage to its blood flow, and for thick ureter, it can be free in segments. Ureteral cyst treatment: the cyst is too large can be resected through the bladder, the base is retained 12.5px, to avoid damage to the lower renal ureteral opening, the cyst is small, not dealt with for the time being, near the bladder at the level of the duplicated ureter cut off the posterior year, in the ureteral stump before the ligation of the ureteral stump, inward under a silicone tube, deep inside the cyst, the negative pressure to aspirate the fluid, the cyst atrophies; for the cyst to come out of the external orifice of the urethra, combined with the obstruction of the person, can be used for the cyst decortication surgery. Prognosis] The treatment effect of this malformation is relatively satisfactory, urinary dribbling disappears immediately after the operation, urinary tract infection symptoms, soon be controlled, the child urinates freely, growth and development are not affected.