Reflux nephropathy

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Female urinary tract

Male urinary tract

Vesicoureteral reflux

Voiding cystourethrogram

Reflux nephropathy is a condition in which the kidneys are damaged by backward flow of urine into the kidney.

Chronic atrophic pyelonephritis; Vesicoureteric reflux; Nephropathy - reflux; Ureteral reflux

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:

• Bladder infections (cystitis)
• Bladder stones
• Bladder outlet obstruction
• Neurogenic bladder
• Abnormal ureters

In some cases, reflux nephropathy produces no symptoms. It is often discovered when a child is evaluated 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.