Urine flows from the kidneys, through the ureters, and into the bladder. Each ureter has a one-way valve where it enters the bladder, preventing urine from flowing back up the ureter. Reflux nephropathy occurs when these valves fail, allowing urine to flow back up to the kidney. If the bladder is infected or the urine contains bacteria, the kidney is exposed to the possibility of infection (pyelonephritis ). Because the pressure in the bladder is generally higher than in the kidney, the reflux of urine exposes the kidney to unusually high pressure. Over time, this increased pressure will damage the kidney and cause scarring. Reflux may occur in people whose ureters do not extend very far into the bladder. The ureters enter the bladder through "tunnels" in the bladder wall, and the pressure in the bladder normally keeps these tunnels pressed closed. If the bladder-wall tunnels are short or absent, pressure within the bladder can force urine back up the ureter. Reflux may be associated with other conditions including the following: In some cases, reflux nephropathy produces no symptoms. It is often discovered when a child is evaulated for repeat or suspicious bladder infections. If reflux is discovered, the child's siblings may also be evaluated, because reflux can run in families. The degree of reflux -- separated into five different grades -- helps determine how the condition is treated. Simple, uncomplicated reflux often falls into grade I or II. Reflux nephropathy may also occur from temporary swelling that occurs after reimplantation of the ureters during a kidney transplant or because of trauma to the ureter. About 4 out of 1,000 people with no symptoms have reflux nephropathy, while up to 50% of infants and children with urinary tract infections have it. Reflux nephropathy may lead to chronic kidney failure and end-stage renal (kidney) disease. There may be no symptoms if only one kidney is affected or symptoms may be those of a urinary tract infection, nephrotic syndrome, or chronic kindey failure. The risk factors include a personal or family history of reflux, congenital abnormalities of the urinary tract, and recurrent urinary tract infections.
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