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 potentially life-threatening complications. Excess fluid can accumulate in the lungs and extreme changes in blood chemistry can affect the function of the heart and brain. There are three general categories of kidney failure (also called renal failure). They are:
- Acute kidney injury (acute renal failure) — Kidney function stops or is abruptly reduced because of a sudden illness, a medication, a toxin or a 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.
- 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 kidney disease (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 (nephritis). Chronic renal failure also can occur because of long-term exposure to certain toxins or drugs. 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 kidney disease, but occasionally, it also follows acute renal failure.
Symptoms vary depending on the type of renal failure.
- Acute kidney injury (acute renal failure) — Symptoms may include:
- Decreased urine output
- Swelling (edema) resulting from salt and water overload
- High blood pressure
- Lethargy caused by the toxic effects of waste products on brain function
If left untreated, acute renal failure can cause extra fluid to back up behind the heart into the lungs, cardiac rhythm abnormalities, behavioral changes, seizures and coma.
- Chronic kidney disease and end-stage renal failure— 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:
- Poor appetite
- 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 kidney injury, your doctor will watch for symptoms and 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 and signs 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 excess fluid in the lungs
- 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
If you have symptoms or a chronic medical condition that is known to potentially cause kidney failure, your doctor will periodically order blood tests to check on kidney function. 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 kidney injury may go away within a few days simply by stopping a medication or reversing whatever caused the situation. Exactly how long the illness lasts varies considerably from person to person, depending on the cause of the kidney problem. In rare cases, acute kidney injury 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 will want to be sure that your kidneys can handle the dye load. Also your doctor will want you to be well hydrated with either oral or intravenous fluids.
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 kidney injury — Treatment begins with measures to correct the cause of renal failure (shock, hemorrhage, burns, heart attack, etc.). Usually doctors order intravenous fluids to be sure that there is sufficient blood flow to the kidneys. This is not done if there is already severe fluid overload. Medications may be needed to lower high levels of potassium and other blood chemicals. If severe fluid overload or abnormalities in blood chemistry cannot be corrected with medications, emergency 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 often includes:
- A low-protein and low-salt diet
- Medications to adjust blood chemical levels
- Medications to treat high blood pressure
- 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 rare cases, patients with severe high blood pressure or chronic pyelonephritis may need both kidneys removed surgically before a transplant.
When To Call A Professional
Many people with acute kidney injury that progresses to acute renal failure are already hospitalized for their other medical conditions. 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 kidney injury 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 kidney injury.
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.