Acute Kidney Failure

The kidneys are a pair of small organs that lie on either side of your spine at about waist level. They act as filters that keep your blood free of by-products and toxins.

• The kidneys excrete these compounds with water to make urine.
  
  
• They also eliminate excess body water while selectively reabsorbing useful chemicals and allowing waste to pass freely into the bladder as urine.
  
  
• They allow you to continue to consume a variety of foods, drugs, vitamins and supplements, additives, and excess fluids without worry that toxic by-products will build up to harmful levels.

Blood circulates through the kidneys for filtration.

• As the first step in filtration, the blood passes through the glomeruli, a complex structure composed of tiny blood vessels entwined randomly together. Substances present in the blood are selectively filtered across the outer linings of the tiny blood vessels and excreted with water as urine or reabsorbed into tubelike structures (tubules) for further filtration. 
  
  
• The tubules continue filtering blood until all appropriate substances are reabsorbed into the blood and all the waste products are excreted with water as urine.
  
  
• Once urine leaves your kidney, it travels through two 6-inch tubelike ureters to the bladder and out your urethra during urination.
  
  
• In this way, the kidneys regulate the amounts of various substances in your blood and the amount of water in your body.
  
  
• Kidneys also help regulate blood pressure and contribute to red blood cell production.

Kidney failure occurs when the kidneys partly or completely lose their ability to filter water and waste from the blood.

• The build up of toxic substances normally removed from the body by the kidneys can cause dangerous health problems.
  
  
• Acute kidney failure happens rapidly.
  
  
• Another name for kidney is "renal," and another name for kidney failure is renal failure. Mild kidney failure is often called renal insufficiency. 

Acute kidney failure occurs in about 5% of people who are hospitalized for any reason. It is even more common in those receiving intensive care.

Chronic kidney failure results when a disease slowly destroys your kidneys. Destruction occurs over many years, usually with no symptoms until the late stage of kidney failure. In fact, progression may be so gradual that symptoms may not occur until kidney function is less than one tenth of normal.

Causes of acute kidney failure fall into one of the following categories:

• Prerenal - Problems affecting the flow of blood before it reaches the kidneys
  
  
• Postrenal - Problems affecting the movement of urine out of the kidneys
  
  
• Renal - Problems with the kidney itself that prevent proper filtration of blood or production of urine

Prerenal failure

Prerenal failure is by far the most common type of acute renal failure. Your kidneys do not receive enough blood to filter. Prerenal failure can be caused by the following conditions:

• Dehydration - From vomiting, diarrhea, water pills, or blood loss
  
  
• Disruption of blood flow to the kidneys - From a variety of causes
  
  
  • Drastic drop in blood pressure - From major surgery, severe injury or burns, or infection in the bloodstream (sepsis) causing blood vessels to inappropriately relax
    
    
  • Blockage or narrowing of a blood vessel carrying blood to the kidneys
    
    
  • Heart failure or heart attacks causing low blood flow
    
    
  • Liver failure causing changes in hormones that affect blood flow and pressure to the kidney

There is no actual damage to the kidneys with prerenal failure. With appropriate treatment, it usually can be reversed unless the insult to the kidneys is prolonged and damage to the kidney tissue proper occurs. 

Postrenal failure

Postrenal failure is sometimes referred to as obstructive renal failure, since it is often caused by something blocking elimination of urine produced by the kidneys. This problem also can be reversed, unless the obstruction is present long enough to cause damage to kidney tissue.

Obstruction of one or both ureters can be caused by the following:

• Kidney stone
  
  
• Cancer of the urinary tract organs or structures near the urinary tract that may obstruct the outflow of urine
  
  
• Medications

Obstruction at the bladder level can be caused by the following:

• Bladder stone
  
  
• Enlarged prostate (the most common cause in men)
  
  
• Blood clot
  
  
• Bladder cancer
  
  
• Neurologic disorders of the bladder impairing its ability to contract

Treatment consists of relieving the obstruction. Once the blockage is removed, the kidneys usually recover in 1-2 weeks if there is no infection or other problem.

Renal damage

Primary renal damage is the most complicated cause of renal failure. Renal causes of acute kidney failure include those affecting the filtering function of the kidney, those affecting the blood supply to the kidney, and those affecting the kidney tissue that handles salt and water processing. 

Some of the kidney problems that can cause kidney failure include the following:

• Blood vessel diseases
  
  
• Blood clot in a vessel in the kidneys 
  
  
• Injury to kidney tissue and cells
  
  
• Glomerulonephritis
  
  
• Acute interstitial nephritis
  
  
• Acute tubular necrosis

Glomerulonephritis: The glomeruli, the initial filtration system in the kidney, can be damaged by a variety of diseases, including infections. The resulting inflammation impairs kidney function.

• A common example is strep throat. Infection with streptococcal bacteria may damage the glomeruli.
  
  
• Some people with glomerular disorders have dark-colored urine (like cola or tea) and back pain.
  
  
• Other symptoms include producing less urine than usual, blood in your urine, high blood pressure, and body swelling (retaining water).
  
  
• Treatment usually consists of medications and, in some cases, when kidney function falls significantly, dialysis may be needed to remove life-threatening wastes that cannot be excreted.

Acute interstitial nephritis: This is a sudden decline in kidney function caused by inflammation of interstitial kidney tissue, that is, the tissue that primarily handles salt and water rather than filtering of wastes.

• The most common causes are related to medications such as antibiotics, anti-inflammatory medicines (aspirin, ibuprofen, for example), and water pills (diuretics).
  
  
• Other causes include infections and immune-related diseases such as lupus, leukemia, lymphoma, and sarcoidosis.
  
  
• It is usually reversible if the kidney damage is not too severe.
  
  
• Treatment consists of withdrawal of offending drugs, treatment of any infection, and dialysis in cases of very low kidney function.

Acute tubular necrosis: The kidney tubules are damaged and do not function normally.

• This condition accounts for 90% of cases of primary acute kidney failure.
  
  
• Causes include shock (decreased blood supply to the kidneys), drugs (especially antibiotics) and chemotherapy agents, toxins and poisons, and dyes used in certain kinds of x-rays.
  
  
• Some people produce much less urine than usual. Other symptoms of acute tubular necrosis include tiredness, swelling, lethargy, nausea, vomiting, abdominal pain, loss of appetite, and rash. Sometimes there are no symptoms.
  
  
• Treatment depends on the cause of the damage and may consist of discontinuing problem medications, replenishing body fluid levels, and improving blood flow to your kidney.  A diuretic may be given to increase urine production if the total body water level is too high. Medications may be given to correct blood chemistry imbalances.
  
  
• If there is no recovery of your native kidneys and these treatments do not sufficiently substitute for the lost kidney function, you will need regular dialysis or you may be a candidate for kidney transplantation.

The following symptoms may occur with acute kidney failure. Some people have no symptoms, at least in the early stages. The symptoms may be very subtle.

• Decreased urine production
  
  
• Body swelling
  
  
• Problems concentrating
  
  
• Confusion
  
  
• Fatigue
  
  
• Lethargy
  
  
• Nausea, vomiting
  
  
• Diarrhea
  
  
• Abdominal pain
  
  
• Metallic taste in the mouth

Symptoms such as seizures and coma may occur in very severe acute kidney failure.

Many people with acute renal failure notice no symptoms. Even if you have symptoms, the symptoms are nonspecific, meaning they could be caused by many different conditions. A physical examination typically reveals few, if any, abnormal findings.

The kidney failure is often detected from blood or urine tests. These tests might be ordered because you are in the hospital for another reason, because you just don't feel well and can't tell why, or as part of a routine health screening.

• Levels of urea (blood urea nitrogen [BUN]) and creatinine are high in kidney failure of prerenal origin. This is called azotemia.
  
  
• Electrolyte levels in the blood may be abnormally high or low because of improper filtering.
  
  
• When the duration and severity of kidney failure is severe, the red blood cell count may be low. This is called anemia. 

The amount of urine produced over a period of hours may also be measured for quantity as well as quality or amount of wastes being excreted. When kidney tissue is injured, protein and desirable substances may be inappropriately excreted in the urine. In some cases, the amount of urine remaining in the bladder after urination will be measured by inserting a catheter, a thin, rubber tube that drains the bladder.

• Urine retained in the bladder after urinating suggests postrenal failure, usually prostate enlargement in men.
  
  
• The urine may be dark, indicating that creatinine and other substances are concentrated.
  
  
• The urine will be examined under a microscope to detect signs of specific kidney problems. Some of these signs include blood, pus, and solid materials called casts.
  
  
• Electrolyte levels in the urine may help pinpoint the exact cause of the kidney failure.

If the diagnosis is not certain after laboratory tests, an ultrasound of your kidneys and bladder may be done. These can help by revealing signs of specific causes of kidney failure.

In some cases, it is necessary to take tissue samples of your kidneys (biopsy) to find the cause of the renal failure.

Treatment of acute renal failure depends partly on the cause and extent of the failure. You may be referred to a kidney specialist (nephrologist or urologist) for your care. The first goal is to pinpoint the exact cause of the kidney failure, as that will partly dictate the treatment. Secondly, the degree to which accumulating wastes and water are affecting your body will impact treatment decisions about medications and the need for dialysis.

|Self-Care at Home|

Self-treatment of acute kidney failure is not recommended. Kidney failure can be a very serious condition that requires medical care.

• It may be possible to receive some or all of your treatment at home. Treatment in some cases can be administered by a home health nurse under the supervision of your health care provider.
  
  
• In cases in which recovery of kidney function is incomplete, the artificial kidney may be needed to clear excess water and accumulating wastes. This is done by dialysis, a process by which the blood is cleared of wastes and excess water. Dialysis, when needed for acute renal failure, is performed at a hospital or dialysis center. Home dialysis may be appropriate in cases in which kidney failure is permanent and dialysis is needed indefinitely. Dialysis at home is not allowed in some states.

|Medical Treatment|

Treatment is focused on removing the cause of the kidney failure.

Medications and other products you ingest will be reviewed. Any that might harm the kidneys will be eliminated or the dose reduced.

Other treatments will be offered, with the following goals:

• Correct dehydration - Intravenous fluids, with electrolyte replacement if needed
  
  
• Fluid restriction - For those types of kidney failure in which excess fluid is not appropriately eliminated by the kidneys 
  
  
• Increase blood flow to the kidney - Usually related to improving heart function or increasing blood pressure
  
  
• Correct chemistry abnormalities - Keeps other body systems working properly 

If your kidneys do not respond to treatment, and adequate kidney function does not return, you will need to undergo dialysis. Dialysis is done by accessing the blood vessels through the skin (hemodialysis) or by accessing the abdominal cavity through the lining that encases the abdominal organs (peritoneal dialysis). 

• With hemodialysis, you are connected to a machine by a tube running from a conduit created surgically between a large artery and vein. Your blood is circulated through the artificial kidney, which removes toxins and wastes. The blood is then returned to your body.
  
  
• Most people require dialysis 3 times per week.

With peritoneal dialysis, wastes and excess water from the bloodstream cross into the abdominal cavity (peritoneal space) and are eliminated from the body by coursing through a catheter that is surgically implanted (through the skin) into the peritoneal cavity.

Most people with acute kidney failure get better when the cause of the kidney failure is removed or treated and don't require dialysis. Normal kidney function is usually restored, though in some cases, residual damage only allows partial restoration of the kidney function. Such patients may not require dialysis but may need medicines to supplement lost kidney function.

|Follow-up|

Your health care provider will arrange follow-up visits as needed for the underlying cause of your kidney failure and the severity of the disease. He or she will monitor your underlying condition and do appropriate lab tests to be sure that the kidney failure has resolved. Preventive measures may be needed in some situations to prevent the problem from occurring again.

|Prevention|

Yearly physical exams by your health care provider include blood tests and urinalysis to monitor your kidney and urinary tract health. 

Be sure to drink enough fluids to keep your kidneys functioning as they should.

Avoid taking substances that can poison or damage kidney tissues. Ask your health care provider about this.

Persons at risk for chronic kidney disease may need more frequent testing for kidney function and other problems that occur with declining kidney function. Difficulties urinating or blood in the urine should prompt a visit to your physician as soon as possible.

|Outlook|

Recovery from acute kidney failure depends on what caused the disease. If the cause does not stem from damage to kidney tissue itself, you will probably make a full recovery. Partial recovery of function may occur in situations in which the injury does not completely resolve.

|Support Groups and Counseling|

American Association of Kidney Patients
100 South Ashley Drive, Suite 280
Tampa, FL 33602
813-223-7099
800-749-2257
 
American Kidney Fund
6110 Executive Blvd, Suite 1010
Rockville, MD 20852
301-881-3052
800-638-8299
 
National Kidney Foundation
30 East 33^rd St.
New York, NY 10016
212-889-2210
800-622-9010

American Urological Association
1000 Corporate Boulevard
Linthicum, MD 21090
Toll free (US only) 866-RING AUA (866-746-4282)
Phone 410-689-3700
Fax 410-689-3800

|Web Links|

American Association of Kidney Patients
 
American Kidney Fund 
 
National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases
 
National Kidney Foundation

renal failure, acute renal failure, ARF, primary acute renal failure, chronic renal failure, CRF, acute interstitial nephritis, acute tubular necrosis, azotemia, dialysis, glomerulonephritis, hemodialysis, obstructive renal failure, renal insufficiency, kidneys, acute kidney failure, diabetes

Author: Rebecca J Schmidt, DO, FACP, Section Chief, Associate Professor, Department of Medicine, Section of Nephrology, West Virginia University School of Medicine and Medical Center.

Coauthor(s): Robert C Harwood, MD, MPH, Program Director, Chair, Department of Emergency Medicine, Christ Hospital and Medical Center; Assistant Professor, Department of Emergency Medicine, University of Illinois at Chicago Medical School.

Editors: Bradley Fields Schwartz, DO, FACS, Director, Center for Urologic Laparoscopy and Endourology, Associate Professor of Urology, Department of Surgery, Southern Illinois University; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, ; Martin I Resnick, MD, Lester Persky Professor and Chair, Department of Urology; Professor, Department of Oncology, Case Western Reserve University School of Medicine.