What is chronic kidney disease?

Chronic kidney disease¹, also called CKD, is a condition that occurs when the kidneys are damaged and can’t filter wastes from the blood the way they should. The disease is chronic because the damage to your kidneys happens slowly over a long period of time.

The kidneys² are part of the urinary tract. They play a vital role in the filtration of wastes and excess fluids from the blood. Advanced-stage chronic kidney disease can cause dangerous levels of fluids, electrolytes, and other wastes to build up in the body.

It is estimated that 15%³ of adults in the United States have chronic kidney disease. The two leading causes of kidney failure, diabetes and high blood pressure, are responsible for roughly 3 out of 4 new cases of chronic kidney disease.

The early stages of chronic kidney disease may not cause any noticeable symptoms. You may not even realize you have CKD until your kidney function has become significantly impaired.

Treatment for chronic kidney disease is aimed at slowing the progression of kidney damage. This is usually achieved by controlling the disease’s underlying cause.

In some cases, chronic kidney disease can progress to end-stage kidney failure. Without artificial filtering treatment (dialysis) or kidney transplant, end-stage kidney failure is fatal.

What are the kidneys, and what do they do?

The kidneys⁴ are two bean-shaped, fist-sized organs. They are located just below the rib cage on either side of the abdomen. Each kidney is made up of roughly one million filtering units called nephrons, which help filter wastes from the blood.

The kidneys are part of the urinary tract, which also includes the ureters, bladder, and urethra. This tract’s job is to filter wastes and pass them through the body in the form of urine.

Healthy kidneys perform a number of vital functions. They filter about half a cup of blood every minute, removing waste and extra water to make urine. Filtered urine then passes from the kidneys to the bladder through tubes called ureters and out of the body through the opening called the urethra.

The kidneys help balance the blood’s concentration of water, salts, and minerals (such as sodium, calcium, phosphorus, and potassium). This balance is vital to ensuring the healthy functioning of your balance, nerves, muscles, and other body tissues.

Your kidneys also perform a number of other functions, including making hormones that help control blood pressure, producing red blood cells, and maintaining bone health.

Hypertensive chronic kidney disease

Hypertensive chronic kidney disease⁵, also called hypertensive nephrosclerosis, refers to a condition in which hypertension (high blood pressure) has damaged the kidneys.

Chronic kidney disease and hypertension are closely related. After diabetes, hypertension is the second leading cause of kidney failure in the United States.

Hypertension⁶ can damage the kidneys’ blood vessels and reduce their ability to work properly. In people with hypertension, the body’s blood vessels stretch in order to accommodate blood flow more easily. Eventually, this stretching leads to scarring. It weakens the blood vessels throughout the body, including those in the kidneys.

When the blood vessels in the kidneys are damaged, it can become difficult for the organs to properly remove wastes and extra fluids from the body. An excess fluid concentration in the blood vessels can cause blood pressure to rise even higher, creating a dangerous cycle.

The best way to prevent hypertensive chronic kidney disease is to manage and lower your blood pressure. Reaching and maintaining a healthy blood pressure may require a combination of medication therapy and lifestyle changes, including:

• Eating a healthy diet
• Getting sufficient physical activity
• Reaching or maintaining a healthy weight
• Quitting smoking
• Managing stress in healthy ways

Chronic kidney disease causes

Along with high blood pressure, diabetes is a leading cause⁷ of chronic kidney disease. CKD caused by diabetes is referred to as diabetic kidney disease⁸.

Hyperglycemia, or high blood sugar (glucose), affects people with diabetes. This condition causes damage to the kidneys’ filtration system. Over time, untreated or poorly managed hyperglycemia can cause so much damage to occur that the kidneys cannot filter wastes and fluids from the blood as they should.

Other conditions that can contribute to the development of chronic kidney disease include:

• Glomerulonephritis: An inflammation of the kidney's filtering units (glomeruli)
• Interstitial nephritis: An inflammation of the kidney's tubules and surrounding structures
• Polycystic kidney disease (PKD): A genetic disorder that causes cysts to grow in the kidneys
• Prolonged obstruction of the urinary tract: This may be caused by an enlarged prostate, kidney stones, or some forms of cancer
• Vesicoureteral reflux: A condition that causes urine to back up into the kidneys
• Pyelonephritis: Chronic kidney infection

Chronic kidney disease symptoms

The symptoms of chronic kidney disease often develop slowly over time. They are frequently nonspecific, meaning the symptoms of CKD overlap with those caused by other illnesses.

Additionally, because the kidneys are highly adaptable and capable of compensating for damage and lost function, CKD symptoms may not appear until irreversible kidney damage has occurred.

The first sign of chronic kidney disease is often the presence of protein in the urine. This is caused by the protein albumin passing from the blood into the urine as a result of damage to the kidneys’ glomeruli. Healthy kidneys block albumin from passing from the blood into the urine.

Other common symptoms of chronic kidney disease include:

• Nausea or vomiting
• Fatigue or weakness
• Decreased appetite
• Difficulty sleeping
• Changes in how much you urinate
• Decreased mental acuity (brain fog)
• Muscle twitches and cramping
• Swelling in the feet and ankles
• Persistent itchiness
• Hypertension (high blood pressure) that’s difficult to manage
• Chest pain—occurs when fluid builds up around the lining of the heart
• Shortness of breath—occurs when fluid builds up in the lungs

If you experience any of the signs and symptoms of chronic kidney disease, see your healthcare provider. The condition can be life-threatening if left untreated.

Anemia in chronic kidney disease

Anemia⁹ is a condition in which the body has fewer red blood cells than normal. This condition is common among people with chronic kidney disease.

Red blood cells carry oxygen throughout the body and supply it to the body’s tissues and organs. In people with anemia, less oxygen is supplied to these tissues and organs—particularly those in the heart and brain, which damages how they function.

Anemia can occur when the kidneys are damaged and do not make enough erythropoietin (EPO), a hormone that prompts bone marrow to produce red blood cells.

Anemia can begin to develop in the early stages of chronic kidney disease when the patient still has 20–50% of their normal kidney function. Anemia tends to worsen as chronic kidney disease progresses. Most patients with a total loss of kidney function (kidney failure) have anemia.

Depending on the cause, a healthcare provider can treat anemia with one of the following treatments:

• Iron: People with anemia experience low blood iron. The first step in treating anemia is raising low iron levels. Iron pills are often used to increase the blood’s concentration of iron and hemoglobin.
• Erythropoietin: If blood tests indicate that your anemia is most likely caused by kidney disease, one treatment option includes injections of a genetically engineered form of EPO (the hormone that prompts the bone marrow to make red blood cells).
• Red blood cell transfusions: Red blood cell transfusions are used for patients whose hemoglobin levels have fallen too low. Raising the blood’s concentration of red blood cells increases the amount of oxygen available to the body.
• Vitamin B12 and folic acid supplements: Providers may suggest that some patients with CKD and anemia take vitamin B12 and folic acid supplements. These supplements help treat vitamin B12 (or folate) deficiency anemia.

As always, talk to your healthcare provider before beginning to take any new supplements.

Chronic kidney disease complications

Chronic kidney disease can affect almost every part of the body. If left untreated, CKD can lead to health complications, including:

• Fluid retention: This can lead to high blood pressure, swelling in the arms and legs, or an accumulation of fluid in the lungs (pulmonary edema)
• Increased potassium levels: A sudden spike in blood potassium levels, called hyperkalemia, can impair the heart's ability to function and may be life-threatening.
• Heart and blood vessel (cardiovascular) disease
• Weakened bones and an increased risk of bone fractures
• Anemia
• Decreased sex drive, erectile dysfunction, or reduced fertility
• Damage to the central nervous system: This can cause difficulty concentrating, personality changes, or even seizures.
• Decreased immune response, which makes you more vulnerable to infections
• Pericarditis: An inflammation of the membrane that surrounds the heart (pericardium)
• Pregnancy complications that carry health risks for both the mother and the developing fetus
• Irreversible damage to the kidneys (end-stage kidney disease): Surviving with end-stage kidney disease eventually requires dialysis or a kidney transplant.