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

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 become infected (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 can 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 can occur with other conditions, including the following:

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

Reflux nephropathy is often found when a child is checked for repeat or suspicious bladder infections. If reflux is discovered, the child's siblings may also be checked, because reflux can run in families.

The degree of reflux -- separated into five different grades -- helps determine treatment. Simple reflux often falls into grade I or II.

Reflux nephropathy also can occur from temporary swelling after the ureters are reimplanted during a kidney transplant or because of 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.

Some people can have no symptoms from reflux nephropathy. There may be no symptoms if only one kidney is affected. If symptoms do occur, they might be similar to those of a urinary tract infection, nephrotic syndrome, or chronic kidney failure.

Symptoms include:

• Blood in the urine
• Burning or stinging with urination
• Dark or foamy urine
• Feeling that the bladder isn't fully emptying
• Flank pain, back pain, or abdominal pain
• Need to urinate at night
• Repeated urinary tract infections in a female
• Single urinary tract infection in a male
• Urinary frequency/urgency

Other symptoms that can occur with this disease include the following:

• Chills
• Fever
• Nail abnormalities
• Nausea and vomiting
• Urinary hesitancy

The blood pressure may be raised, and there may be signs and symptoms of chronic kidney failure.

Other tests include:

• Abdominal CT scan or ultrasound of the kidneys
• Creatinine clearance
• IVP
• Kidney ultrasound
• Radionuclide cystogram
• Serum BUN
• Serum creatinine
• Urinalysis or 24-hour urine studies
• Urine culture
• Voiding cystourethrogram

Simple, uncomplicated reflux (called primary reflux) less than grade III can be treated by the following:

• Antibiotics
• Careful watching
• Repeated urine cultures
• Yearly ultrasound of the kidneys

More severe reflux may require surgery, such as the following:

• Ureteral reimplantation
• Reconstructive repair

Surgery to place the ureter(s) back into the bladder can be done to stop reflux nephropathy. This surgery results in less frequent and less severe urinary tract infections.

The outcome varies. Most cases of reflux nephropathy get better on their own. However, the damage to the kidney may be permanent. If only one kidney is involved, the other kidney may continue to function.

Reflux nephropathy may cause kidney failure in children and young adults.

• Blockage of the ureter after surgery
• Chronic or repeat urinary tract infections
• Chronic renal failure if both kidneys are involved (can progress to end-stage kidney disease)
• Kidney infection
• High blood pressure
• Nephrotic syndrome
• Permanent damage to one or both kidneys
• Persistent reflux
• Scarring of the kidneys

Call your health care provider if you have symptoms of reflux nephropathy, or if you have decreased urine output or other new symptoms.

Quickly treating conditions that cause reflux of urine into the kidney may prevent reflux nephropathy.