What is a duplicated kidney? In layman’s terms, it is a kidney with two sets of renal structures, two sets of mutually independent pelvic calyx systems. A duplicated kidney malformation has two units, the upper kidney and the lower kidney, which can drain urine from their respective collecting systems by two ureters, called duplicated ureters (the ureters that drain the upper kidney or the lower kidney are called “upper ureters” and “inferior ureter”). In clinical practice, duplicated kidneys are still relatively common. One study found that 1 in 1500 children have a duplicated kidney. Duplicated kidneys can be unilateral or bilateral, with unilateral being more common. They can be classified as complete or incomplete (Y-shaped) depending on whether the two ureters converge or not. Incomplete duplicated ureters can converge at any part of the ureter, more commonly the pelvic ureteral junction is connected or the ureter is connected distally near the level of the bladder. What are the clinical manifestations of duplicated kidney? The clinical manifestations of duplicated kidney and ureteral malformation are varied and can be completely asymptomatic or can present with severe acute symptoms such as abdominal pain. 1.Most (about 60%) incomplete duplicated kidneys have no clinical symptoms at all and are only detected when a comprehensive urinary tract examination is performed. 2, Some patients with duplicated kidney show symptoms such as fever, hematuria and abdominal pain with complications such as pyelitis, kidney stones, tuberculosis, tumor and fluid retention, and are only detected when a complete urinary tract comprehensive examination is performed. 3. Complete type of duplicated kidney duplicated ureteral malformation if the ureter opens in the vulvar vestibule, vagina, etc. The child has a history of urine loss since childhood, wetting the bed at night and often not drying the shorts during the day, although there is again normal urination activity. If there is a history of this condition, a careful examination of the vulva will often reveal an abnormal ureteral opening. Even if an abnormal ureteral opening is not found, an intravenous pyelogram can often confirm this congenital malformation. What tests are needed to diagnose a duplicated kidney? Special attention is needed for the diagnosis. 1. If there is no ectopic opening or complications in duplicated kidney, it is usually asymptomatic and not easy to detect and diagnose. 2.If a female child has normal urination and urinary incontinence, she should be considered to have ureteral ectopic opening and further urinary system examination is needed. 3.Ultrasound combined with CTU examination can clarify the vast majority of duplicated kidneys and duplicated ureters. 4, Cystoscopy in complete type can often see an extra ureteral opening on the affected side, and the one located outside the upper part is often the ureter coming from the low renal pelvis. 5, intravenous urography, if the duplicated kidney is functional, the contrast can show two pelvic calyces; if not functional, only a low kidney is shown. Retrograde urography, if the tube is successfully inserted, the image is clearer and more helpful for diagnosis. 6, female patients with urinary incontinence, should be carefully observed in the vestibule and vagina with or without small hole spray urine. If blue urine is ejected after intravenous injection of indigo carmine, it is more helpful to observe. If the tube can be inserted through this hole for imaging, it can show the ectopic ureter and renal pelvis. 7. If the ureteral ectopic opening is in the urethra, urethroscopy is required. How to treat duplicated kidney? How to choose the surgery method? If there is only simple urinary tract infection without anatomical abnormalities (hydronephrosis, ectopic ureteral opening, etc.), antibiotics are used to control the infection and surgery is usually not needed; 2. If the ectopic openings are bilateral, surgery can be performed in stages; 3. If the repeated ureteral reimplantation is not obvious and there is no obvious damage to the renal parenchyma, ureteral cut-off can be performed and transplanted to the lower group of kidneys or the ureter to which it belongs or the ectopic openings can be reimplanted to the bladder. 4.Nephrectomy should be performed only when all kidneys are destroyed or when partial nephrectomy fails to solve the problem. The choice of surgical method needs to be determined by the specific situation. Most of the cases can be treated by lumpectomy now. What are the conditions that require surgery? ① incomplete duplicated ureter with upper segment renal function present with uretero-ureteral reflux; ② complete duplicated ureter with upper segment renal function present with vesicoureteral reflux; ③ combined uncontrolled urinary tract infection or spot urinary incontinence; ④ obstructive upper urinary tract fluid due to ureteral cross compression, stenosis or combined stone. The principles of surgical treatment are: protection of renal function, effective, safe, and minimally invasive.