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

Urine flows from each kidney, through tubes called ureters, and into the bladder. When the bladder is full, it squeezes and sends the urine out through your urethra. None of the urine should flow back into the ureter when the bladder is squeezing. Each ureter has a one-way valve where it enters the bladder, preventing urine from flowing back up the ureter.

But in some people, the urine flows back up to the kidney. This is called reflux.

Over time, the kidneys may be damaged or scarred by this reflux. This is called reflux nephropathy

Reflux can occur in people whose ureters do not attach properly to the bladder or if the valves do not work well. Children may be born with this problem or other birth defects of the urinary system that cause reflux nephropathy.

Reflux nephropathy can occur with other conditions that lead to a blockage of urine flow, including:

• Bladder outlet obstruction
• Bladder stones
• Neurogenic bladder, which can occur in people with multiple sclerosis

Reflux nephropathy also can occur from swelling of the ureters after a kidney transplant or trauma to the ureter.

The risk factors include a personal or family history of reflux, abnormalities of the urinary tract, and repeat urinary tract infections.