What is kidney disease?


About your kidneys.

Healthy kidneys play a vital role in keeping us alive and well. The kidneys do three important things for us:

  1. Prevent the buildup of wastes and extra fluid in the body.
  2. Keep electrolytes, such as sodium, potassium, and phosphate, balanced.
  3. Produce hormones that do three things:
    1. Regulate blood pressure.
    2. Make red blood cells.
    3. Keep bones strong.

What is kidney disease?

Kidney disease means the kidneys are damaged and cannot filter blood as they should. As a result, waste and extra fluid build up in the body, causing harm to other organs. If kidney disease is not detected and treated, it can lead to many serious and life-threatening problems, including:

  • Cardiovascular disease (heart attack, angina, coronary heart disease, stroke)
  • Pulmonary edema (fluid buildup in the lungs)
  • High blood pressure
  • Weakened bones that can easily break
  • Decreased ability to fight off infections
  • Anemia
  • Nerve damage
  • Kidney failure

For most people, kidney damage occurs slowly over many years. This is called chronic kidney disease (CKD). As the disease progresses, it becomes more difficult for the kidneys to function properly, eventually leading to kidney failure. Once the kidneys fail, a person must either begin dialysis (machine treatment to help kidneys work), or have a kidney transplant to stay alive.
When someone has a sudden drop or change in kidney function, because of an injury or illness, this is called acute kidney injury (AKI). This can occur in a person with healthy kidneys or in someone who already has kidney problems. If not found and treated, AKI can quickly lead to kidney failure. Learn more about AKI.
What are the symptoms of kidney disease?
Early kidney disease often has no symptoms. In fact, many people are not diagnosed until just before their kidneys fail. That is why it is so important to get checked. Possible symptoms of kidney disease may include:

  • More frequent urination
  • Blood in your urine
  • Tiredness
  • Muscle cramps
  • Foot swelling
  • Chest pain
  • Shortness of breath
  • Dry, itchy skin

These symptoms may also be due to another illness or condition. If you have any of these symptoms, call your doctor. The only way to know if you have kidney disease is to get checked.

The effects of kidney disease

Kidneys perform many jobs that keep you healthy. Your kidneys:

  • Clean your blood and remove extra fluid and waste products.
  • Help control your blood pressure.
  • Make red blood cells that carry oxygen throughout your body and take carbon dioxide back to your lungs so it can be exhaled.
  • Help your body use vitamin D to keep your bones strong.
  • Balance your electrolytes and minerals so that your muscles, heart, and organs work properly.

When your kidneys are damaged, they cannot perform these important functions. The good news is that kidney disease can be prevented and treated to keep from getting worse.

Heart and Blood Vessels

Kidney disease increases your risk of heart and blood vessel problems such as high blood pressure, heart attack, congestive heart failure, blood vessel disease, stroke, and swelling and extra fluid around the heart. Heart attacks are the most common cause of hospitalization and death for people with kidney disease, especially those on dialysis.
Heart disease also affects the kidneys. Heart failure reduces blood flow to the kidneys and can lead to kidney failure.

Kidney disease increases your risk of nerve damage and seizures.
Uremic encephalopathy (disorder of the brain) happens when toxins that are normally removed by the kidneys build up in the brain. This can cause neurological problems like confusion, loss of concentration, lethargy, subtle personality changes, and other mental problems.

Bones and Joints
Kidney disease causes an imbalance of minerals in the blood and prevents your body from using vitamin D to keep bones strong. Bones become weaker, thinner, and more likely to break.
Kidney disease can also cause pain, stiffness, and extra fluid in the joints where bones connect.

Body Fluids
When the kidneys don’t work properly, extra fluid and toxins build up in the body. This can cause edema (swelling) in your legs, arms, eyes, and around your lungs and heart.
Kidney disease also can cause an imbalance of electrolytes (sodium, potassium, phosphates) and lead to irregular heartbeat, muscle weakness, edema, and uremia (blood in the urine). Uremia can have serious effects, including loss of appetite, nausea, vomiting, fluid buildup around the heart, nerve problems, confusion, and changes in mental status. Left untreated, uremia can result in seizures, coma, cardiac arrest, and death.

Kidney disease decreases your ability to make red blood cells. This leads to anemia, which causes extreme fatigue and can make heart problems worse.
Hemolytic uremic syndrome happens when red blood cells die and block the blood vessels around the kidneys. Damage to these blood vessels can lead to excessive bleeding and other problems.

Immune System
Kidney disease weakens your immune system and makes it harder to fight off illness and infection.

Kidney disease gets worse over time and affects many organs and body systems.
When left untreated, kidney disease can progress to end-stage renal disease, when the only treatments available to prevent kidney failure are dialysis or transplant.
Early detection and treatment of kidney disease can prevent or delay poor outcomes. Ask your doctor to check your kidneys.

What is acute kidney injury?

Acute kidney injury (AKI) is a sudden decline in kidney function caused by one or more of the following:

  • Lack of blood flow to the kidneys
  • Direct damage to the kidneys
  • Blockage of urine from the kidneys

AKI happens quickly, usually within a few hours or days. When it happens, your kidneys lose the ability to filter waste and extra fluid from your body. As a result, toxins build up, potentially causing great harm to other organs and body systems. Early detection and treatment are very important to (1) promptly identify reversible conditions, such as a blockage causing urine to back up into the kidneys, and (2) prevent serious problems.

Left untreated, AKI can lead to many serious conditions, such as:

  • Cardiovascular disease (heart attack, angina, coronary heart disease, stroke, pericarditis, hypertension)
  • Edema (pulmonary, extremities)
  • Neurologic (nerve damage, uremic encephalopathy)
  • Weakened bones that can easily break
  • Decreased ability to fight off infections
  • Anemia Uremia
  • Metabolic acidosis
  • Electrolyte imbalance
  • Kidney failure

What are the symptoms of AKI?
As with chronic kidney disease (CKD), there may not be any signs or symptoms that show in the early stages of AKI. Anyone who is at increased risk should be tested immediately.
Warning signs may include any of the following:

  • Decreased urine output
  • Fluid retention
  • Swelling in the arms or legs
  • Fatigue or drowsiness
  • Confusion
  • Nausea
  • Shortness of breath
  • High blood pressure
  • Irregular heartbeat
  • Flank pain (pain in upper abdomen or back)
  • Chest pain or pressure
  • Seizures or coma, in severe cases

If you have any of these symptoms, ask your doctor to check your kidneys.

What causes AKI?
While AKI usually occurs in connection with another disease or condition, such as chronic kidney disease (CKD), diabetes, or heart disease, it can also occur in people with normally functioning kidneys. Everyone is at risk, but some are at increased risk.
You are at risk if you have a sudden decrease in blood flow to the kidneys. This can result from a number of causes including other illnesses; being anemic or dehydrated; overuse of aspirin, ibuprofen, or other medications that harm the kidneys; burns; circulatory shock; and trauma. In the U.S., AKI is very common among hospitalized patients, as it can result after cardiac or other major surgeries as well as exposure to sepsis. Approximately 45 percent of patients in the Intensive Care Unit (ICU) develop AKI.1
You are also at risk of AKI if you have a condition in or around your kidneys that causes damage to their filtering system, resulting in a sudden loss of kidney function. Some of these conditions are:

  • Glomerulonephritis (inflammation of the filtering units of the kidneys)
  • Acute tubular necrosis (damage to the tiny tube that recycles sodium and potassium)
  • Acute interstitial nephritis (reduces the kidneys’ ability to filter properly)
  • Vascular disease (can lead to blood clots in the arteries and veins near the kidneys)
  • Vasculitis (an inflammation of the blood vessels)
  • Lupus (an immune system disorder)

If you have a blockage in your urinary tract that forces urine to back up into the kidneys, you are at risk for AKI. Some conditions that may cause this include:

  • Blood clots in the urinary tract
  • Kidney stones
  • Enlarged prostate
  • Colon, prostate, bladder, or cervical cancer

How do I know if I have AKI?
AKI is detected through two simple tests:

  • A blood test that measures the amount of creatinine (a waste product produced by muscle activity) in the blood. It indicates how well your kidneys are filtering this waste. 
  • A urine test that measures the amount of urine being produced. This indicates whether there is damage or an obstruction that is blocking urine flow.

Once AKI is identified, further tests will be done to determine the cause, which may be reversible or treatable. You will want to discuss the appropriate additional tests with your doctor. Examples of further testing may include:

  • Physical exam to identify signs of congestive heart failure or infection
  • Patient history to identify use of medications that damage the kidneys
  • Blood urea nitrogen (BUN) test to tell how well your kidneys and liver are working
  • Complete blood count (CBC)
  • Blood test to measure electrolytes (minerals in the body), which need to be balanced to perform vital body functions
  • Estimated glomerular filtration rate (eGFR) to measure kidney function
  • Ultrasound to rule out obstruction

Treatment will focus on the underlying illness or injury as well as, the management of complications of AKI, such as dehydration, swelling, urinary obstruction, overload of potassium or calcium in your body, or problems with blood pressure. Your doctor will continue to monitor you by measuring the creatinine in your blood and your urine output. Even when your condition is under control, you should receive a follow-up evaluation within three months of the AKI episode and be monitored for the long term.


  • All patients who are at risk for AKI should ask their doctor to check their kidneys.
  • Make sure your doctor has a current list of all medicines you are taking, including over-the-counter drugs. You will want to avoid overuse of aspirin or ibuprofen, as they can cause harm to the kidneys.
  • Drink water to stay well-hydrated.
  • Adopt and maintain healthy behaviors. o Be physically active.
    • Eat a healthy diet that is low in fat, salt, and sugar.*
    • Avoid tobacco products.
  • Keep other health problems under control. 
    • If you have diabetes, keep your blood sugar in your target range.
    • Keep your blood pressure in your target range.
    • Keep your cholesterol and other lipids (fats) in your target range
    • If you have frequent bladder infections, take steps to prevent them and get treated quickly.
    • Take medicines as prescribed.
  • Get your yearly physical exam, and ask your doctor to check your kidneys.

*If you have AKI or CKD, you should meet with a dietitian who specializes in nutrition for kidney conditions.

1 Li PKT, Burdmann EA, and Mehta RL. Acute kidney injury: Global health alert. J Nephropathol 2(2):90-97. April 2013. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3891141/

Last updated November 1, 2017