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 valve-like mechanisms between the ureters and bladder 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 that 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 keep 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:
Reflux nephropathy may not produce any obvious signs. Reflux is often discovered when a child with repeat or suspect bladder infections is evaluated radiologically. If reflux is discovered the child's siblings may also be evaluated, because reflux can run in families.
The degree of reflux, often separated into five different grades may help determine how the condition is treated. Simple, uncomplicated reflux often falls into the grade I or II category.
Reflux nephropathy may also occur from temporary swelling after surgical reimplantation of ureters during kidney transplant or because of trauma to the ureter.
Reflux nephropathy occurs in about 4 out of 1,000 asymptomatic individuals. However, in infants and children who experience urinary tract infections, its prevalence approaches 40% to 50%. Reflux nephropathy may lead to chronic renal failure and end-stage renal disease. The symptoms may not be present if only one kidney is affected or may be those of urinary tract infections, nephrotic syndrome, or chronic renal failure.
The risk factors include a personal or family history of reflux, congenital abnormalities of the urinary tract, and recurrent urinary tract infections.
