What is kidney failure?

Renal failure, also referred to as kidney failure¹, is a condition that occurs when the kidneys are damaged and no longer function as well as they should. This can lead to high blood pressure, fluid retention, and the inability to properly filter wastes from the body.

While kidney failure refers to many problems², technically speaking, kidney failure occurs when 85–90%³ of your kidney function is gone.

The kidneys are two bean-shaped organs located on either side of the abdomen. Healthy kidneys perform many important tasks. They clean the blood, remove wastes and excess water from the body, help make red blood cells, and regulate blood pressure.

Generally, kidney failure occurs when the organs are damaged. This can be caused by a physical problem, such as kidney stones or scar tissue, or a disease, such as high blood pressure, diabetes, glomerulonephritis (damage to the tiny filters in the kidneys), or polycystic kidney disease damage.

Unfortunately, there is no cure for kidney failure. However, treatments exist to help perform the kidneys’ normal function, and many people with kidney failure still live long, productive lives. If you have kidney failure, you’ll have to make lifestyle changes to help manage your condition and symptoms.

What is chronic kidney disease?

Chronic kidney disease⁴, or CKD, is a condition characterized by the gradual loss of the kidneys’ function.

The early stages of the disease may not present any signs or symptoms. For this reason, you may not know that you have chronic kidney disease until your kidney function has been significantly impacted.

The progression of chronic kidney disease may lead to kidney failure. Having chronic kidney disease also increases your risk of stroke and heart attack.

How common is kidney failure? (h3)

More than 661,000⁵ people in the United States have kidney failure. Of these individuals, 468,000 receive dialysis treatment, while 193,000 have received a successful kidney transplant.

Approximately 1 in 10 people⁶ has chronic kidney disease. This condition becomes more common with age: after reaching age 40, a person’s kidney filtration abilities begin to fall by roughly 1% each year. This can be attributed to the natural aging of the kidneys and the fact that many of the conditions that can damage the kidneys (including high blood pressure, diabetes, and heart disease) are common in older people.

As this condition commonly runs in families, studies are being conducted to investigate the relationship between genetics and kidney failure.

1 in 3⁷ U.S. adults are at increased risk for developing kidney disease, largely due to pre-existing health conditions. Your healthcare provider can help you determine your risk for kidney failure and how frequently you should be tested.

Acute kidney failure

Acute renal (kidney) failure⁸ is a condition that occurs when kidney function rapidly declines. They lose their ability to filter wastes from the blood, which can cause wastes to accumulate at dangerous levels.

Acute kidney failure usually develops over the course of just a few days and is usually only temporary. It most commonly develops in patients who are being hospitalized—especially those who are seriously ill and require intensive care.

Some common causes⁹ of acute kidney failure include:

• Severe dehydration
• Obstruction in the urinary tract, such as a kidney stone
• Autoimmune kidney diseases
• Certain medications
• Uncontrolled or insufficiently managed systemic diseases, such as heart disease or liver disease

Because this condition can be life-threatening, it requires intensive medical treatment. It is not always fatal, however; acute kidney failure may be reversed and, if you are generally healthy, you may recover most or all of your original kidney function.

Kidney failure in cats and dogs

The signs and symptoms of chronic kidney disease in pets¹⁰ can vary—they may be mild and slow to progress or severe and sudden. Some common signs of CKD in cats and dogs include:

• Polydipsia (drinking too much water) and polyuria (urinating in large quantities)
• New or worsened incontinence (leaking of urine), particularly during the night
• Vomiting and/or diarrhea
• Lack of appetite
• Weight loss
• Depression or malaise (which is related to elevated levels of wastes in the blood)
• Anemia (low red blood cell count), which can cause pale gums and weakness
• Weakness (caused by low blood potassium levels)

Some other less common signs and symptoms include:

• Weakened bones, which can cause fractures
• High blood pressure (hypertension), which can lead to sudden blindness
• Itchiness (caused by calcium and phosphorus deposits on the skin)
• Bleeding into the stomach or gut
• Bruising

Because our pets can’t tell us when something is wrong, it’s important that you closely monitor them if you notice any changes in their behavior. Keep an eye out for dehydration and increased fluid consumption, weight loss, pale gums, and oral ulcers, as these may all be indicators of kidney problems.

If you notice changes in your pet’s behavior or appearance, he or she will need to undergo blood and urine testing to determine whether these changes are caused by CKD.

As with humans, animals with CKD cannot be cured of the disease. However, treatments may be used to keep your pet hydrated and reduce waste products (through intravenous drug treatment) and replace substances that are low (like potassium). Some treatments involve feeding your pet a special diet tailored to address his or her disease. The treatment your veterinarian recommends will depend on the severity of your pet’s signs and symptoms and the progression of their CKD.

What causes kidney failure?

Healthy kidneys¹¹ regulate the body by removing excess fluids and filtering minerals and other wastes. They also help produce red blood cells and hormones and regulate biometrics like blood pressure.

When the kidneys are damaged, they cannot perform these vital functions. This may cause your blood pressure to rise or your body to retain excess fluids.

Some causes¹² of chronic kidney disease (which may lead to kidney failure) are:

• Diabetes: Unmanaged or untreated diabetes can cause elevated blood sugar levels (hyperglycemia). Excess blood sugar can damage multiple organs, including the kidneys.
• High blood pressure (hypertension): This condition occurs when your blood pressure—the force of blood flowing through your blood vessels—is consistently too high. Over time, high blood pressure that’s not properly treated can damage kidney tissues.
• Polycystic kidney disease: This hereditary (genetic) condition causes cysts to grow inside the kidneys.
• Glomerular diseases, including glomerulonephritis, can decrease the kidneys’ ability to filter wastes.
• Autoimmune diseases, such as lupus, can affect multiple body systems and contribute to CKD.

Acute kidney failure causes

Acute kidney failure (also called acute kidney injury) occurs when the kidneys suddenly lose function, generally over the course of a few hours or days.

Some common causes¹³ of acute kidney failure include:

• Damage to the kidneys: The kidneys may be damaged by a number of factors and conditions, including blood clots in the veins and arteries within and surrounding the kidneys, infections, glomerulonephritis, certain medications, and the breakdown of muscle tissues (rhabdomyolysis) or tumor cells (tumor lysis syndrome).
• Slowed blow flow to the kidneys: Some conditions and injuries can impair the flow of blood to the kidneys, damaging the organs. These include heart attack and heart disease, anaphylaxis (a severe, potentially life-threatening allergic reaction), severe dehydration, infections, and liver failure.
• Blocked urine in the kidneys: Some conditions that block urine from passing out of the body (called urinary obstructions) can cause acute kidney failure. These include kidney stones, bladder cancer, urinary tract blood clots, nerve damage, prostate cancer, and an enlarged prostate.

Risk factors for kidney failure

The same risk factors that increase your likelihood of developing kidney disease put you at a higher risk for kidney failure.

The most common risk factors¹⁴ for kidney disease and kidney failure include:

• Diabetes: This condition is one of the two biggest risk factors¹⁵ for kidney disease and the leading cause of kidney failure. Ongoing hyperglycemia (high blood sugar), a condition that affects people with diabetes, damages the kidneys’ filtration system. Over time, poorly managed hyperglycemia can cause so much damage that the kidneys can no longer filter wastes and fluids from the blood properly.

• High blood pressure: High blood pressure, or hypertension¹⁶, is the other biggest risk factor for kidney disease and the second most common cause of kidney failure. Hypertensive chronic kidney disease¹⁷, also called hypertensive nephrosclerosis, refers to a condition in which hypertension (high blood pressure) has damaged the kidneys.

• Age: People over the age of 60 are at higher risk of developing kidney disease. This is due to the fact that the kidneys’ function declines naturally with age. Additionally, older patients have a higher incidence of high blood pressure and diabetes.
• Genetics: Your likelihood of developing kidney disease is higher if someone else in your family has had it. Understanding your family health history¹⁸ is an important part of evaluating your risk for kidney problems.

• Race/ethnicity: People of certain races and ethnicities, including African-Americans, Hispanics, Native Americans, and Asian Americans, are at higher risk¹⁹ for kidney disease than others. Research has not determined why this is the case, although it may be due to a higher incidence of high blood pressure and diabetes in these populations. Some underlying health conditions also contribute to kidney disease and kidney failure, including:

• Polycystic kidney disease: A genetic disorder that causes cysts to grow in the kidneys
• Glomerulonephritis: An inflammation of the kidney's filtering units (glomeruli)
• Autoimmune diseases, such as lupus and Berger’s disease (IgA nephropathy²⁰)

• Acute kidney injury
• Kidney cancer

Kidney failure symptoms

The early stages of kidney disease may not present with any symptoms. As the kidneys are damaged and begin to fail, however, wastes and excess fluid begin to build up in the bloodstream. This can cause you to feel sick and lead to the following symptoms²¹:

• Unexpected weight loss
• Nausea
• Difficulty sleeping
• Decreased appetite
• Tiredness and weakness
• Itchiness
• Muscle cramps, especially in the legs
• Swelling in the feet or ankles
• Anemia (a low red blood cell count)

See your healthcare provider if you experience any of the signs or symptoms of kidney disease or kidney failure. They will be able to provide you with the proper diagnosis and treatment.

Kidney disease stages

Kidney failure is also referred to as end-stage renal disease²² (ESRD). ESRD is the last stage of chronic kidney disease, a condition in which the kidneys can no longer properly filter the blood due to long-term damage.

Patients with kidney failure require dialysis (artificial filtering treatments) or kidney transplants to survive.

A patient’s GFR, or glomerular filtration rate, is used to assess the severity of their kidney disease. A GFR indicates how well the kidneys can perform their normal filtration processes. The presence of proteinuria (excess protein in the urine) is also used to establish the stage of a patient’s kidney disease.

Kidney disease can be assigned one of the following stages:

• Normal kidney function: The kidneys are healthy, and no damage has occurred. Normal GFR level of 90+mL/min.
• Stage 1: Kidney damage with normal kidney function. GFR level of 90+mL/min and at least 3 months proteinuria.
• Stage 2: Kidney damage with mild loss of kidney function. GFR 60–89mL/min and at least 3 months proteinuria.
• Stage 3: Mild-to-severe loss of kidney function. GFR to 30–59mL/min.
• Stage 4: Severe loss of kidney function. GFR to 15–29mL/min.
• Stage 5 (end-stage renal disease): Kidney failure requires dialysis or transplant for survival. GFR less than 15mL/min.

Kidney disease takes years to progress²³. Furthermore, not all patients progress from Stage 1 of kidney disease to Stage 5.

Kidney failure complications

Kidney failure can lead to a number of health complications²⁴, including:

• Anemia: Occurs when the body does not produce enough red blood cells (which the kidneys help with)
• Bone disease and high phosphorus (hyperphosphatemia): Damaged kidneys may not be able to play their normal role in keeping the bones healthy.
• Inflammation of the pericardium (the lining of the heart), which can cause chest pain
• A buildup of fluid in the lungs, which can lead to shortness of breath
• Muscle weakness caused by an imbalance in fluids and electrolytes
• Death: Premature death caused by pre-existing conditions, such as cardiovascular disease, is much higher in adults with chronic kidney disease. Heart disease is the most common cause of death²⁵ in people undergoing dialysis.