1, vesicoureteral reflux concept The normal ureteral bladder junction only allows urine to enter the bladder from the ureter and prevents urine from flowing backwards. When this live valve-like function is impaired for some reason, urine flows backwards into the ureter and kidney, a phenomenon called ? vesicoureteral reflux? Vesicoureteral reflux can be divided into primary and secondary, the former is due to incomplete activation of the ureteral-vesical junction; the latter is secondary to lower urinary tract obstruction, such as posterior urethral valve disease, neurogenic bladder, etc. 2, vesicoureteral reflux pathogenesis (1) normal anatomy and anti-reflux mechanism of the uretero-vesical junction The ureteral muscle layer is composed of spiral muscle fibers, and only the muscle fibers of the bladder wall segment are longitudinal, and after entering the bladder, the muscle fibers form a fan to form the superficial layer of the muscle of the triangle, and extend forward to the posterior urethra of the seminal vesicle. As the ureter penetrates the bladder wall, it is encircled by a fibrous sheath (Waldeyer) that is fixed outside the bladder to the outer membrane of the ureter and attaches inferiorly to the deeper layers of the triangle, with the ureter in the middle, allowing adaptation to the filling and emptying of the bladder. The segment of the ureter that passes through the bladder wall into the lumen lies under the bladder mucosa and opens into the bladder triangle. The unidirectional activation of the ureteric bladder junction depends on the length of the submucosal segment of the ureter and the ability of the musculature of the triangle to maintain this length; on the other hand, there is sufficient support of the posterior wall of this segment of the ureter by the forcepsis muscle. When the pressure in the bladder rises, the submucosal segment of the ureter is compressed without regurgitation, and this activation mechanism is passive. There are also active aspects, such as the peristaltic ability of the ureter and the ability of the ureteral orifice to close, which also play a part in preventing reflux. (2) Reasons for the occurrence of reflux The submucosal segment of the ureter has defective longitudinal muscle fibers, resulting in the outward migration of the ureteral orifice and shortening of the submucosal segment of the ureter, thus losing the ability to resist reflux. In the absence of normal reflux, the ratio of the length of the submucosal segment of the ureter to its diameter is 5:1, whereas in the presence of reflux it is less than 2:1. Lyon et al. suggested that abnormal ureteral orifice morphology is another cause of reflux, and there are four types of ureteral orifice morphology, namely, crater, sports field, horseshoe, and golf hole. Except for the crater shape, the other three types are abnormal reflux ureteral orifice morphology. In addition, paraureteral diverticulum, ureteral opening in bladder diverticulum, ectopic ureteral orifice, and bladder dysfunction can affect the anti-reflux mechanism causing vesicoureteral reflux. 3, vesicoureteral reflux grading Reflux grading relies on voiding cystourethrography (VCUG), which often shows a more severe degree of ureteral dilatation than those with intravenous urography. The International Reflux Study Group classifies reflux into five degrees. Grade I: reflux reaches only the lower ureter; Grade II: reflux to the renal pelvis and calyces, but no dilatation; Grade III: mild dilatation and tortuosity of the ureter, mild dilatation of the renal pelvis and mild blunting of the fornix; Grade IV: moderate dilatation and tortuosity of the ureter, moderate dilatation of the renal pelvis and calyces, but most of the calyces maintain the papillary pattern; Grade V: severe dilatation and tortuosity of the ureter, severe dilatation of the renal pelvis and calyces, and disappearance of the papillary pattern of most of the calyces. 4. Relationship between vesicoureteral reflux and urinary tract infection, renal scarring, etc. Reflux makes part of the urine remain in the urinary tract after the bladder is emptied, providing a pathway for bacteria to travel up from the bladder to the kidney, so reflux often leads to urinary tract infection. It can manifest as clinical symptoms of acute pyelonephritis or as an asymptomatic chronic pyelonephritic process. Renal scarring often occurs in children with recurrent urinary tract infections, often in the upper pole of the kidney with a pestle-like dilatation of the calyces. Ninety-seven percent of children with renal scarring have vesicoureteral reflux, so the term “reflux nephropathy” is now widely used to describe this abnormality. New scarring always occurs in children with recurrent urinary tract infections, and the more severe the reflux, the higher the chance of progressive scarring or new scarring. Renal scarring can occur quickly or after a long period of time. 5. Effects of vesicoureteral reflux on the body The effects of vesicoureteral reflux on renal function are similar to the effects of partial urinary tract obstruction on the kidneys. The internal pressure in the upper urinary tract increases during reflux, and the distal part of the renal unit suffers from it first, so the tubular function is impaired earlier than the glomerulus. Aseptic reflux affects the tubular concentrating capacity and lasts longer. The effect of infection on tubular concentrating capacity recovers within 6 weeks after infection eradication; reflux impairs renal concentrating capacity and improves after reflux disappears. Glomerular function is affected in the presence of renal parenchymal damage and is proportional to the degree of renal parenchymal damage. Patients with reflux who have renal scarring have an increased chance of developing hypertension in adulthood. Renal failure occurs with reflux and renal scarring, mainly in patients suffering from bilateral renal scarring with hypertension. 6. What are the common clinical symptoms? Early symptoms are mostly urinary tract infection symptoms, such as fever, cloudy urine, pus urine, etc. Heavy cases may be accompanied by drowsiness, weakness, anorexia, nausea, vomiting and growth retardation. Older children, especially those with renal scarring, may be seen for hypertension. Infants and children may have renal colic and pressure pain in the kidney area. Older children may have pain in the spine or kidney area during bladder filling or urination, and older children may also have pain and tenderness in the spine when acute pyelonephritis is present. 7. Common imaging tests A voiding cystourethrography is an important tool in the diagnosis of vesicoureteral reflux. VCUG should be performed whenever an infant has a single urinary tract infection. Its an accurate and effective method for determining the diagnosis and grading of reflux, called the gold standard, and can be repeated. Voiding cystourethrography must be performed 2-3 weeks after the infection has resolved. Ultrasonography is also of interest to measure thickness and to determine renal growth. Blunted renal calyces and dilated ureters may be a sign of severe vesicoureteral reflux. A renal nuclear scan can show renal scarring and is used to follow the child for new scar formation, to compare renal function before and after surgery, and to evaluate glomerular and tubular function. Cystoscopy is not performed as a routine examination and can be used to understand the morphology and location of the ureteral orifice, the length of the submucosal segment of the ureteral bladder, the paraureteral diverticulum, and whether the ureter opens into the bladder diverticulum or the ectopic ureteral orifice before deciding to continue conservative treatment with medications.