In kidney failure, the kidneys lose their ability to filter enough waste products from the blood and to regulate the body's balance of salt and water. Eventually, the kidneys slow their production of urine, or stop producing it completely. Waste products and water accumulate in the body. This can lead to a potentially life-threatening overload of fluids (such as congestive heart failure), a dangerous accumulation of waste products in the blood, and extreme changes in blood chemistry that eventually can affect the function of the heart and brain. There are three types of kidney failure (also called renal failure). They are:

• Acute renal failure. Kidney function stops or is abruptly reduced because of a sudden illness, a medication or medical condition that causes one of the following:
  
  
  • A severe drop in blood pressure or an interruption in the normal blood flow to the kidneys, which can occur during major surgery, severe burns with fluid loss through burned skin, massive bleeding (hemorrhage) or a heart attack that severely affects heart function. Blood clots that travel to the kidney also can cause acute kidney failure.
  • Direct damage to kidney cells or to the kidneys' filtering units, which can be caused by inflammation in the kidneys, toxic chemicals, medications, contrast dye used for computed tomography (CT) scans and certain procedures (such as angiograms) that are guided by x-ray, and infections.
  • Blocked urine flow from the kidney, which can occur because of obstructions outside the kidney, such as kidney stones, bladder tumors or an enlarged prostate.


• Chronic renal failure. Kidney function gradually declines, usually over a period of years. It is most commonly caused by illnesses such as diabetes, uncontrolled high blood pressure or chronic kidney inflammation. Examples of conditions that cause inflammation in the kidney include glomerulonephritis and pyelonephritis. Chronic renal failure also can occur because of long-term exposure to lead, mercury or certain drugs, especially painkillers. Some forms of chronic renal failure run in families, so your doctor will ask you about family members' medical problems.



• End-stage renal disease. This also is called end-stage renal failure. This occurs when kidney function has deteriorated to the point that if dialysis treatments do not begin, the person will die. This is usually the end result of longstanding chronic renal failure, but occasionally, it also follows acute renal failure.

Symptoms vary depending on the type of renal failure.

• Acute renal failure. Symptoms include:
  
  
  • Decreased urine output
  • Swelling (edema) resulting from salt and water overload
  • High blood pressure
  • Nausea
  • Vomiting
  • Lethargy caused by the toxic effects of waste products on brain function
  
  If left untreated, acute renal failure can cause congestive heart failure (because the extra fluid backs up behind the heart into the lungs), cardiac rhythm abnormalities, behavioral changes, seizures and coma.



• Chronic renal failure and end-stage renal disease. Because the kidney damage in chronic renal failure occurs slowly over a long time, symptoms develop slowly, usually beginning when more than 80% of kidney function is lost. When this occurs, symptoms can include:
  
  
  • Headache
  • Fatigue
  • Weakness
  • Lethargy
  • Itching
  • Poor appetite
  • Vomiting
  • Increased thirst
  • Pale skin
  • High blood pressure
  • Slowing of growth in children
  • Bone damage in adults

If you have an illness or medical condition that increases the risk of acute renal failure, your doctor will monitor you closely for symptoms or signs of kidney failure. He or she may give you blood and urine tests and measure the amount of urine you produce. If you have a chronic (long-term) medical condition that increases the risk of long-term kidney damage, your doctor will check your blood pressure and look for symptoms of chronic renal failure during regularly scheduled office visits.

To confirm the diagnosis of acute renal failure, your doctor will order tests of your urine and blood tests to check for chemical abnormalities. Levels of these chemicals are elevated in people with poor kidney function. Other tests may include:

• A chest X-ray to check for signs of heart failure
• X-rays of the abdomen or an ultrasound examination of the kidneys to check for a urinary tract obstruction
• A kidney biopsy, in which a sample of kidney tissue is removed and examined in a laboratory

Your doctor may suspect that you have chronic renal failure if you have symptoms or a chronic medical condition that is known to cause this problem. Because chronic renal failure typically develops gradually, a physical examination may be normal. To confirm the diagnosis of chronic renal failure, the same evaluation may be recommended as for acute renal failure, including tests of blood and urine, ultrasound of kidneys and in some cases, a kidney biopsy.

Doctors diagnose end-stage renal disease when symptoms become pronounced and certain blood chemicals reach very high levels in the blood, indicating that kidney function has been severely affected.

Acute renal failure may go away on its own, and some people recover within a matter of days. Exactly how long the illness lasts varies considerably from person to person, depending on the cause of the kidney problem. In rare cases, acute renal failure progresses to end-stage renal disease.

Chronic renal failure is a lifelong problem that can worsen over time to become end-stage renal disease. End-stage renal disease is a permanent condition that can be treated only with dialysis or a kidney transplant.

Many forms of kidney failure cannot be prevented. People who have diabetes, high blood pressure or coronary artery disease should try to control the illness with appropriate diet, medication and lifestyle changes. Before a computed tomography (CT) scan or angiogram procedure that uses contrast dye, your doctor may prescribe a protective medication, acetylcysteine (Mucomyst), if there are special concerns about your risk for kidney damage. If you already have chronic kidney failure, treating medical problems such as diabetes and high blood pressure and avoiding medications and other treatments that can further damage the kidneys may prevent worsening of kidney function. If you have chronic kidney failure, you should tell any physician who treats you.

Treatment depends on the type of kidney failure.

• Acute renal failure. Treatment begins with measures to correct the cause of renal failure (shock, hemorrhage, burns, heart attack, etc.). After this has begun, more specific kidney treatment may include fluids given intravenously (into a vein) to correct any abnormal fluid loss, medicines called diuretics that increase urine output, limited fluids by mouth, a diet low in protein and high in carbohydrates, medications to adjust high or low levels of blood chemicals such as potassium, and medications to control high blood pressure. If severe high blood pressure, severe fluid overload, congestive heart failure, symptoms of altered brain function or severe abnormalities in blood chemistry occur, short-term dialysis may be necessary.



• Chronic renal failure. People with chronic renal failure are monitored closely with frequent physical examinations, blood pressure checks and blood testing. Treatment includes a low-protein and low-salt diet, medications to adjust blood chemical levels, medications to treat high blood pressure and sometimes a hormonal medication called erythropoietin (Epogen, Procrit) to correct anemia (a low level of red blood cells).



• End-stage renal disease. End-stage renal disease is treated with dialysis. Dialysis must continue indefinitely, or until a suitable donor can be found for a kidney transplant. Dialysis mechanically removes waste products from the blood. In patients with severe high blood pressure or chronic pyelonephritis, both kidneys may need to be removed surgically before a transplant.

Many people with acute renal failure already are hospitalized for their other medical conditions when kidney failure develops. Other people should call a health care professional whenever the amount of urine they produce either increases or decreases markedly. In people with decreased urine output, swelling of the face and ankles is another danger sign, especially if there is also shortness of breath. For people with chronic renal failure, it is a good idea to check with your health care professional whenever a new medication is prescribed.

Most children with acute renal failure have a good outlook for recovering their kidney function, although in rare cases, end-stage renal disease can develop. Among adults, the chances of recovery depend primarily on the underlying reason for acute renal failure rather than the renal failure itself. Among people who recover, about 50% have some permanent kidney damage, but in most cases, this is not severe enough to cause symptoms.

People with chronic renal failure may have a continuing decrease in kidney function, but not everyone develops end-stage renal disease. For those who do, the time it takes for end-stage renal disease to develop varies from person to person.

National Institute of Diabetes and Digestive and Kidney Disorders
Office of Communications and Public Liaison
Building 31, Room 9A06
31 Center Drive, MSC 2560
Bethesda, MD 20892-2560
Phone: 301-496-3583
http://www.niddk.nih.gov/

National Kidney Foundation
30 East 33rd St.
New York, NY 10016
Phone: 212-889-2210
Toll-Free: 1-800-622-9010
Fax: 212-689-9261
E-Mail: info@kidney.org
http://www.kidney.org/