(I) Vesicoureteric reflux Vesicoureteric reflux (VUR) is an abnormal physiological phenomenon of urine reflux from the bladder to the ureter or renal pelvis and calyces caused by various primary or secondary causes.VUR is prone to ureteric and renal hydrops, secondary infections and stones, which impairs renal function, which in turn can lead to renal scarring, renal atrophy, renal failure, and so on. A series of reflux nephropathy (RN), which progresses to end-stage renal disease (ESRD) in severe cases, is one of the main reasons for pediatric dialysis and kidney transplantation. This guideline focuses on the epidemiology, etiology, diagnosis, and treatment of primary VUR pediatrics, and does not elaborate on secondary VUR. Epidemiology] The incidence of pediatric VUR in China is about 0.6%. 25%-40% of children with VUR have pyelonephritis, and the average age at diagnosis is 2-3 years. The incidence of neonatal VUR is higher in boys than in girls, but with age, the incidence of VUR in girls is gradually higher than that in boys, and the average incidence of VUR is 4-6 times higher than that in boys. VUR is more common in children under 5 years of age and less common in older children. Etiology] The cause of VUR may be multifactorial, including race and genetics, age, etc. The incidence of VUR in white people is higher than in black people. The incidence of VUR is 10 times higher in white than in black populations, up to 30% in siblings of children with VUR, and up to 70% in the offspring of patients with VUR. Primary VUR is most common in pediatric patients, and its etiology includes congenital hypoplasia of the muscularis propria of the vesicoureteral wall segment, congenital shortening or deficiency of the submucosal ureter of the bladder, ectopic ureteral openings, and congenital anomalies of the Waldeyers’ sheaths, all of which can result in incomplete function of the valves at the vesicoureteral junction, leading to the development of VUR. Diagnosis] I. Clinical manifestations Urinary tract infection is the most common clinical symptom, and the possibility of VUR should be considered in children under 5 years of age with recurrent urinary tract infections. Children may exhibit urinary frequency, urgency, pain and fever. When aseptic reflux occurs, children may present with renal colic and pain in the lower back when the bladder fills or urinates. Some children present with symptoms of acute pyelonephritis, manifesting as low back pain and fever on the affected side. Children with bilateral severe VUR are prone to renal hypertension. Second, auxiliary examination (a) Urine routine and bacterial culture (recommended) Urine routine can determine whether the patient has urinary tract infection, and bacterial culture + drug sensitivity can help to select antibiotics for rational treatment. (ii) Voiding cystourethrography (VCUG) (recommended) VCUG is the basic method to confirm the diagnosis of VUR and the standard technique for grading. Based on the results of VCUG, the International Reflux Study Committee classifies VUR into five grades: Grade I: urine reflux into the non-dilated ureter. Grade II: urine reflux to the non-dilated pelvis and calyces. Grade III: Mild or moderate dilatation of the ureter, renal pelvis, and calyces with mild blunting of the cup. Grade IV: Moderate ureteral tortuosity and dilatation of the renal pelvis and calyces. Grade V: severe dilatation of the ureter and renal pelvis and calyces with loss of papillae; ureteral tortuosity; reflux in the renal parenchyma.The grading of VUR reflux helps in the selection of treatment options. (iii) Renal scintigraphy (recommended) Technetium-dimercaptosuccinic acid (99mTc-DMSA) scintigraphy assesses cortical function of both kidneys and serves as an indirect means of diagnosing reflux per se, detecting reflux-associated renal damage, changes in acute pyelonephritis, and following up with and without renal scarring. Renal scarring was categorized into four grades based on the photographic signs of 99mTc-DMSA scanning: grade I: one or two scars, grade II: more than two scars but normal renal parenchyma between the scars, grade III: diffuse damage throughout the kidneys in the type of obstructive nephropathy manifesting itself in the form of total renal atrophy, with or without scarring of the renal silhouettes, and grade IV: end-stage, atrophic kidneys with little or no DMSA uptake (less than 10 percent of total renal function). Grade IV: End-stage, atrophic kidney, little or no DMSA uptake (less than 10% of total renal function). (Urodynamics (optional) Urodynamics is used in cases of urinary incontinence or positive residual urine in order to confirm functional abnormalities of the lower urinary tract. Urodynamic examination is more important in cases of secondary reflux due to posterior urethral valves confirmed by fundoplication or VCUG. (v) Cystoscopy (optional) Cystoscopy is of little value in the diagnosis of VUR. In patients who are to be treated non-surgically, cystoscopy may be useful to visualize other anatomical abnormalities such as double ureteral malformations and ectopic ureteral openings. (vi) Ultrasonography (ultrasound) (optional) Ultrasound can be used to initially assess the morphology and parenchymal thickness of both kidneys and renal ureteral fluid. However, ultrasound has limitations in detecting renal scarring and cannot grade VUR. (vii) Intravenous pyelogram (IVU) (optional) IVU can show the hydronephrosis of kidney and ureter, assess the thickness of renal parenchyma and the presence of urological malformations, but the sensitivity of diagnosing renal scar is lower than that of radionuclide scanning. 【Treatment】 The principle of VUR treatment is to prevent urinary tract infection, and to prevent sustained impairment of renal function and related complications. Specific treatment should be selected according to the patient’s clinical symptoms, degree of VUR reflux, renal function of the affected side, age, presence of urinary tract malformations, and complications. (i) Watchful waiting For children <1 year old, watchful waiting is possible. Because with age, 81% of children with degree I-II and 48% of children with degree III-V, VUR has the potential to subside naturally. Children with reflux should urinate regularly; avoid holding urine; encourage secondary urination, because of the presence of reflux, after the first urination, reflux of urine into the ureter and back to the bladder, so the child needs to urinate again after 2 to 3 minutes. In male children, if the foreskin is too long, circumcision is feasible. (For children aged 1 to 5 years with reflux grade of Ⅰ to Ⅲ, drug treatment can be given first. The principle of treatment is to prevent infection and damage to the kidneys. Children should be given long-term prophylactic antibiotics in small doses with low nephrotoxicity, broad-spectrum and high efficiency to control the infection. Medication should be maintained until the reflux disappears. Imaging should be performed regularly during treatment. (C) Surgical treatment Surgical indications: ① 1 to 5 years old children, reflux grade Ⅳ ~ V degree; ② > 5 years old female children; ③ I ~ Ⅲ degree of children in the follow-up process, the reflux grade aggravated; ④ medication is not effective in controlling urinary tract infections or recurrent urinary tract infections; the presence of urinary tract abnormalities such as ectopic ureteral openings. Surgical treatment includes open surgery, laparoscopic surgery, and endoscopic treatment. 1, open surgery The principle of surgery is to extend the length of the ureter under the bladder mucosa and re-establish the anti-reflux mechanism. Currently, the more commonly used surgical procedures are Lich-Gregoir, Politano-Leadbetter, Cohen, Psoas-Hitch, etc. The success rate of the operation can be as high as 92% to 98%. Cohen vesicoureteral reanastomosis is most commonly used, that is, after incision of the bladder, fully free a section of the diseased ureter, this section of the ureter is buried in the bladder mucosa, forming a new tunnel, so that the bladder submucosal ureter is prolonged, to achieve the purpose of anti-reflux. 2, laparoscopic surgery There are some small samples of laparoscopic surgery to treat VUR. although the follow-up showed that the postoperative efficacy is comparable to that of open surgery, the learning curve of laparoscopic surgery is long, and the operation time is significantly longer than that of open surgery. Therefore, laparoscopic surgery is not recommended as routine surgical treatment. 3, endoscopic treatment In recent years, there are some reports of using biological materials such as polytetrafluoroethylene gel, polydimethylsiloxane, polyglycolic anhydride/hyaluronic acid copolymer, etc., which can be injected endoscopically into the mucosa of the bladder under the ureter to change the morphology of the ureteral orifice or tighten the opening of the ureter to achieve the purpose of anti-reflux. A recent Meta-analysis showed that after endoscopic injection treatment, the cure rate of children with VUR of degree I-II, III, IV, and V reached 78.5%, 72%, 63%, and 51%, respectively. Although the near-term efficacy of endoscopic treatment is still acceptable, the long-term effect needs to be further studied. 4.Postoperative complications Common complications include no improvement of VUR after surgery, postoperative ureteral stenosis, hematuria, sepsis, and postoperative anuria. Follow-up] Children treated with medication need to be closely monitored and followed up until the reflux disappears. Routine follow-up includes monitoring the child’s blood pressure, renal function and urine routine and bacterial culture. VCUG is performed after 12 to 18 months of treatment, and surgical treatment can be considered if the reflux does not improve significantly. The follow-up of children with VUR after surgical treatment is mainly to know the effect of surgery and the presence of surgical complications such as ureteral stenosis. However, the specific follow-up items and follow-up time limit have not been clearly reported in domestic and international literature, and are not yet uniform, which can be arranged in accordance with the local medical conditions and according to the specific conditions of the patients. Usually, VCUG follow-up is optional after endoscopic treatment, and ultrasonography can be performed 3 months after surgery to exclude upper urinary tract obstruction, and subsequent follow-up should include blood pressure measurement and urinalysis. (Renal cystic disease Renal cystic disease is a group of diseases characterized by “cystic lesions” in the kidneys. The majority of renal cystic diseases are congenital, while a few are acquired and uncharacterized. Renal cystic disease is categorized in Table 1.