What is chronic kidney disease?

Kidney problems can develop suddenly (acute) or over the long term (chronic). Many conditions, diseases, and medicines can create situations that lead to acute and chronic kidney problems. Acute kidney injury, which used to be called acute renal failure, is more commonly reversible than chronic kidney failure.

• Acute kidney injury (AKI) is usually caused by an event that leads to kidney malfunction. Common causes include serious infection, blood loss from major surgery or injury, or the use of some medicines.
• Chronic kidney disease (CKD) is usually caused by a long-term disease, such as high blood pressure or diabetes, that slowly damages the kidneys and reduces their function over time.

The presence or lack of symptoms may help your doctor determine whether acute kidney injury or chronic kidney disease is present.

• Symptoms of decreased kidney function, such as fluid buildup or electrolyte imbalance, are more likely to develop with acute kidney injury, regardless of how long the kidney has been malfunctioning. Symptoms may reflect the actual cause of the kidney problem.
  • An obstruction in the urinary tract may cause pain in the side or lower back (flank pain), blood in the urine, or reduced urine output.
  • Dehydration may cause extreme thirst; lightheadedness or faintness; a weak, rapid pulse; and other symptoms.
• Symptoms of chronic kidney disease may not develop until very little kidney function remains. Other problems may develop with chronic kidney disease, such as anemia and increased levels of phosphorus in the blood (hyperphosphatemia), along with complications caused by kidney failure. These complications often do not develop until kidney disease has been present for some time.

Most cases of acute kidney injury occur in people who are already in the hospital for other reasons. In these people, acute kidney injury is usually diagnosed when routine tests show a sudden increase in creatinine and blood urea nitrogen (BUN) levels. A buildup of these waste products in the blood points to a decrease in kidney function. Your doctor will compare these levels to previous tests to find out if your kidney problem is acute or chronic.

An ultrasound of the kidneys also may help determine whether kidney problems are acute or chronic. Normal-sized kidneys may be present in either condition, but when both kidneys are smaller than normal, chronic kidney disease is usually the problem.

At first with chronic kidney disease, your kidneys are still able to regulate the balance of fluids, salts, and waste products in your body. But as kidney function decreases, you will start to have other problems, or complications. The worse your kidney function gets, the more complications you'll have and the more severe they will be.

When kidney function falls below a certain point, it is called kidney failure. Kidney failure has harmful effects throughout your body. It can cause serious heart, bone, and brain problems and make you feel very ill.

After you have kidney failure, either you will need to have dialysis or you will need a new kidney. Both choices have risks and benefits.

Many people with chronic kidney disease don't have symptoms. If your kidneys get worse and start to fail, you may:

• Have swelling and weight gain. This is from the extra fluid in your tissues. It is called edema (say "ih-DEE-muh").
• Often feel sick to your stomach (nauseated) or vomit.
• Have trouble sleeping.
• Urinate less than normal.
• Have trouble thinking clearly.
• Feel very tired.

The first step is to treat the disease that's causing kidney damage, which is often diabetes or high blood pressure. Controlling blood sugar and blood pressure may slow kidney damage. You will probably need to take medicine. Lifestyle changes are also important to help slow kidney disease.

Dialysis is a mechanical process that performs the work that healthy kidneys would do. It clears wastes and extra fluid from the body and restores the proper balance of chemicals (electrolytes) in the blood. When chronic kidney disease becomes so severe that your kidneys are no longer working properly, you may need dialysis.

You may use dialysis for many years. Or it may be a short-term measure while you are waiting for a kidney transplant.

The two types of dialysis used to treat severe chronic kidney disease are:

Hemodialysis.

This type uses a man-made membrane called a dialyzer to clean your blood. You are connected to the dialyzer by tubes attached to two blood vessels. Before treatments can begin, a surgeon creates a site where blood can flow in and out of your body. This is called the dialysis access. Usually the doctor creates the access by joining an artery and a vein in the forearm or by using a small tube to connect an artery and a vein. An access may be created on a short-term basis by putting a small tube into a vein in your neck, upper chest, or groin.

Peritoneal dialysis.

This type uses the lining of your belly (peritoneal membrane) to clean your blood. Before you can begin, a surgeon needs to place a catheter in your belly to create the dialysis access.

Learning about dialysis is an important step in preparing for dialysis. Most dialysis clinics offer predialysis services to help you know about your choices.

Your doctor will do blood and urine tests to see how well your kidneys work. You'll be asked if you've had past kidney problems or have a family history of kidney disease. You may have an imaging test, such as an ultrasound. Your doctor may also take a tiny sample (biopsy) of kidney tissue.

Although medicine cannot reverse chronic kidney disease, it's often used to help treat symptoms and problems caused by kidney disease. Medicines are also used to slow further kidney damage.

Medicines can be used to treat problems such as:

• Anemia. Erythropoiesis-stimulating (ESA) therapy and iron replacement therapy can be used.
• A buildup of fluid. Diuretics are used for this.
• High blood pressure. ACE inhibitors, angiotensin II receptor blockers (ARBs), beta-blockers, or calcium channel blockers may be used.
• Electrolyte imbalances.
• Protein in your urine or heart failure. Medicines used may include ACE inhibitors and ARBs.

Medicines, like ESA therapy and iron, may be used during dialysis to treat anemia. Anemia often develops in advanced chronic kidney disease. Your doctor might also suggest taking vitamin D to help keep your bones strong.

If you have a kidney transplant, you'll have to take medicines called immunosuppressants. They help prevent your body from rejecting your new kidney.

Health professionals who can diagnose and treat chronic kidney disease include:

• Family medicine physicians.
• Internists.
• Kidney specialists (nephrologists).
• Pediatricians.
• Nurse practitioners.
• Physician assistants.

If you are diagnosed with chronic kidney disease, you will likely be referred to a nephrologist for treatment.

You may also be referred to a:

• Surgeon, if you need a dialysis access site or if you are being considered for a kidney transplant.
• Registered dietitian. He or she can help you with meal planning and choosing foods that are best for people with this disease.
• Psychologist or social worker. They can help you and your family with emotional stress or financial issues.

There are things you can do to slow the progression of chronic kidney disease. For example, manage your blood pressure and, if you have diabetes, your blood sugar. Stay at a healthy weight and follow your eating plan. Be active. Don't smoke and limit alcohol. And avoid taking medicines that can harm your kidneys.

If you have chronic kidney disease that gets worse, you may be able to have a kidney transplant. You might be considered a good candidate if you don't have significant heart, lung, or liver disease or other diseases, such as cancer, which might decrease your life span.

Most experts agree that it's the best option for people with kidney failure. In general, people who have kidney transplants live longer than people treated with dialysis.

You may have to wait for a kidney to be donated. If so, you will need to have dialysis while you wait. Also, it may be hard to find a good match for your blood and tissue types. Sometimes, even when the match is good, the body rejects the new kidney.

After a kidney transplant, you will have to take medicines called immunosuppressants. These medicines help prevent your body from rejecting your new kidney.

The main factors that put you at risk of chronic kidney disease include:

• Having high blood pressure, diabetes, or a family history of either. These conditions can damage the small blood vessels in the kidneys. They are the major causes of chronic kidney disease.
• Being in the obese weight range.
• Taking certain medicines that can damage kidneys over the long term. Examples are pain relievers called NSAIDs and certain antibiotics.
• Being older. The kidneys begin to work less well as people age.
• Being African American or Native American.
• Being male.

Healthy kidneys keep the right balance of minerals in your blood. This includes potassium.

If you have long-term (chronic) kidney disease, it is hard for your kidneys to control the amount of potassium in your blood. You may get too much potassium. This can be harmful.

In some cases, other medicines may make your body get rid of too much potassium. If this happens, you may need to take a potassium supplement.

Chronic kidney disease is caused by damage to the kidneys. The most common causes of this damage are:

• Diabetes. High blood sugar levels caused by diabetes can damage blood vessels in the kidneys. If blood sugar stays high over many years, this damage slowly reduces kidney function.
• High blood pressure. If it isn't treated, high blood pressure can damage blood vessels, which can lead to damage in the kidneys. Blood pressure often rises with chronic kidney disease.

Other things that can lead to chronic kidney disease include:

• Kidney diseases you were born with, such as polycystic kidney disease.
• Kidney infections.
• A narrowed or blocked renal artery. This artery carries blood to the kidneys.
• Long-term use of medicines that can damage the kidneys, such as ibuprofen and some antibiotics.

Many medicines may impair kidney function and cause kidney damage. If you have chronic kidney disease, your doctor may advise you to continue to take a medicine but may change how much you take. Or you may change to a different medicine. Make sure you talk with your doctor before you start or stop any medicine.

Medicines that may need to be avoided, adjusted, or changed include:

• Pain medicines, including:
  • Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen.
  • Acetaminophen and aspirin may be harmful if overused. They are usually safe in small amounts.
• Herbal supplements. They can contain minerals like potassium that are harmful for people who have kidney disease. Many herbs can interact with prescription medicines.
• Statin medicines, such as lovastatin and simvastatin.
• Diabetes medicines, including insulin and metformin.
• Heartburn and upset-stomach medicines, such as Milk of Magnesia and Alka-Seltzer.
• Antimicrobial medicines, including some antibiotics, anti-fungal, and antiviral medicines.

Long-term (chronic) kidney disease happens when the kidneys cannot remove waste and keep your body's fluids and chemicals in balance. Usually, the kidneys remove waste from the blood through the urine. When the kidneys are not working well, waste can build up so much that it poisons the body. Kidney disease can make you very tired. It also can cause swelling, or edema, in your legs or other areas of your body.

High blood pressure is one of the major causes of chronic kidney disease. And kidney disease can also cause high blood pressure. No matter which came first, having high blood pressure damages the tiny blood vessels in the kidneys.

If you have high blood pressure, it is important to lower it. There are many things you can do to lower your blood pressure, which may help slow or stop the damage to your kidneys.

Having chronic kidney disease means that for some time your kidneys haven't been working the way they should. Your kidneys filter your blood. When your kidneys don't work as they should, they can't filter your blood well enough to keep you healthy.

The stages of chronic kidney disease are determined mostly by the estimated glomerular filtration rate (eGFR). Glomerular filtration is the process by which the kidneys filter the blood, removing excess wastes and fluids. The eGFR is a calculation that determines how well the blood is filtered by the kidneys. It is one way to measure kidney function. Your doctor will also use a test that measures the amount of protein in your urine and the cause of your kidney disease to guide your treatment.

The eGFR is often calculated using a formula that includes a person's age, sex, and serum creatinine levels. An eGFR under 60 mL/min/1.73 m² may indicate kidney disease. The lower the eGFR number, the worse the kidney function. This number is an estimate. It may not be a good measure of kidney health in some people, such as the very young or very old, amputees, or obese people. In some cases, eGFR may also be estimated with a 24-hour urine collection.

Chronic kidney disease is defined as either kidney damage or an eGFR of less than 60 for longer than 3 months.

You can learn how much potassium is in certain foods. Then you can control how much potassium you get in your diet.

Your doctor or dietitian can help you plan a diet that gives you the right amount of potassium. There is no diet that is right for everyone. Your diet will be based on how well your kidneys are working and whether you are on dialysis.

Your diet may change as your disease changes. See your doctor for regular testing. Testing helps you know when to change your diet. Your doctor or dietitian can help you do this.

Changing your diet can be hard. You may have to give up many foods you like. But it is very important to make the recommended changes. They will help you stay healthy for as long as possible.