Kidney failure happens when the kidneys can no longer remove enough waste and extra fluid from the blood or keep important minerals balanced. This can cause waste and fluid to build up and affect other parts of the body. Kidney failure may develop suddenly after an illness or injury, or gradually over time. Treatment depends on the cause and may include medicines, dialysis, or a kidney transplant.
What happens when the kidneys stop working properly?
The kidneys are two bean-shaped organs that filter the blood and produce urine. They remove waste products and extra water while maintaining the right balance of salts and minerals, such as sodium and potassium. They also help control blood pressure, support red blood cell production, and maintain healthy bones. According to MedlinePlus, when the kidneys lose too much of their normal function, waste and fluid can build up, leading to problems throughout the body.
Kidney failure means the kidneys can no longer perform these essential jobs well enough to maintain the body's normal balance without additional medical support. In advanced chronic kidney disease, it generally refers to kidney function that has fallen to around 15% of normal or less. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that this level of kidney function may lead to a buildup of waste and excess fluid and may require kidney replacement treatment or other supportive care.
Can kidney failure happen suddenly or develop over time?
Kidney failure can develop in two main ways. The speed of onset matters because sudden kidney problems and long-term kidney damage may need different investigations and treatments.
Acute kidney injury
Acute kidney injury (AKI), sometimes called acute kidney failure, is a sudden decline in kidney function. It can develop over hours or days during a serious illness, after significant fluid loss, or when blood flow to the kidneys falls. A blockage in the urinary tract or certain medicines can also contribute. According to the NHS, many people recover after the underlying problem is treated, although some experience lasting kidney damage. Severe cases may require temporary dialysis.
Chronic kidney failure
Chronic kidney failure develops when kidney function declines over a longer period, usually as a result of chronic kidney disease (CKD). Damage may progress over months or years, and early kidney disease often causes no noticeable symptoms. Treatment can sometimes slow further loss of kidney function, but advanced chronic damage may not be reversible. When the kidneys can no longer maintain the body's needs, treatment may be required to replace some of their lost function or manage the effects of kidney failure.
What causes kidney failure?
The underlying cause depends partly on whether kidney function declines suddenly or gradually. Some conditions directly damage kidney tissue, while others interfere with blood flow to the kidneys or prevent urine from draining normally.
- Diabetes: High blood sugar over time can damage the kidneys and is a leading cause of chronic kidney disease and kidney failure in adults.
- High blood pressure: Persistently high blood pressure can damage kidney blood vessels and reduce their ability to filter blood effectively.
- Severe dehydration, blood loss, or low blood pressure: These problems can reduce the blood supply reaching the kidneys and contribute to acute kidney injury.
- Serious infections or illness: Severe infections, including sepsis, can cause an abrupt decline in kidney function.
- Urinary tract blockage: Kidney stones, an enlarged prostate, or other obstructions may prevent urine from draining properly.
- Other kidney diseases: Inflammatory conditions, inherited disorders, and other diseases affecting kidney tissue may lead to long-term damage.
- Certain medicines: Some medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), can contribute to kidney injury in particular circumstances. A healthcare professional can review medication risks and safer options when needed.
Having a risk factor does not mean kidney failure will necessarily develop. However, people with diabetes, high blood pressure, heart disease, or a family history of kidney failure may benefit from kidney function testing at intervals recommended by their healthcare professional.
What are the symptoms of kidney failure?
Symptoms depend on how quickly kidney function changes and how much function remains. Chronic kidney disease may produce few noticeable symptoms in its early stages. When kidney function becomes significantly impaired, waste products, excess fluid, and mineral imbalances can cause a range of problems.
- Swelling in the feet, ankles, legs, or sometimes around the eyes.
- Passing much less urine than usual.
- Unusual tiredness, weakness, or reduced energy.
- Nausea, vomiting, reduced appetite, or an unpleasant change in taste.
- Persistent itching or dry skin.
- Muscle cramps or weakness.
- Shortness of breath, which may be associated with excess fluid in the body or other medical problems.
- Difficulty concentrating, unusual drowsiness, or confusion in more advanced cases.
These symptoms can occur with many conditions and are not specific to kidney failure. Some people have kidney dysfunction without feeling unwell, so the absence of symptoms does not rule out a kidney problem. A sudden major reduction in urine, new confusion, or breathlessness needs urgent medical assessment. Severe difficulty breathing or sudden confusion warrants emergency medical help.
How do doctors diagnose kidney failure?
Healthcare professionals consider a person's medical history, symptoms, examination findings, urine output, and test results. They also compare current results with earlier measurements when available. This helps determine whether kidney function has changed suddenly or declined over time and whether another condition may be contributing.
According to the NIDDK's guidance on kidney disease testing, blood and urine tests are central to assessing kidney health. Common investigations include:
- Blood creatinine and estimated glomerular filtration rate (eGFR): Creatinine is a waste product that the kidneys remove from the blood. The eGFR estimates how effectively the kidneys filter blood.
- Urine tests: Urinalysis can identify blood, protein, or other abnormalities. A urine albumin test can help detect kidney damage.
- Electrolyte and other blood tests: These may identify imbalances in potassium, sodium, and other substances that the kidneys help regulate.
- Imaging tests: An ultrasound or another scan may be used when a blockage, structural problem, or other cause needs investigation.
A single test result does not always explain the cause or full extent of a kidney problem. For chronic kidney disease, the pattern of results over time is particularly important. In suspected acute kidney injury, a rise in creatinine compared with the person's usual level, together with other clinical findings, can help identify a sudden decline in function.
How is kidney failure treated?
Treatment aims to address the underlying cause, manage complications, and support the kidney function that remains. The approach depends on whether the problem is acute or chronic, how much kidney function has been lost, and the person's overall health.
Treating acute kidney injury
When kidney function declines suddenly, treatment focuses on the cause. This may involve treating an infection, correcting fluid loss or low blood pressure, reviewing medicines that may be contributing, or relieving a urinary blockage. More serious cases may require hospital care and dialysis for a limited period. Some people recover much or all of their kidney function, while others are left with ongoing kidney problems and need follow-up testing.
Managing advanced chronic kidney failure
For advanced chronic kidney failure, treatment may include medicines, an individualized eating and drinking plan, and close monitoring of blood pressure, electrolytes, anemia, and other complications. A kidney specialist can help plan for treatment that replaces some lost kidney function when needed. The NIDDK's guide to kidney failure treatment options describes the main approaches:
- Hemodialysis: Blood passes through a filter in a machine that removes waste and extra fluid before returning the blood to the body.
- Peritoneal dialysis: The lining of the abdomen acts as a filter, allowing waste and excess fluid to be removed using dialysis fluid placed in the abdominal cavity.
- Kidney transplantation: Surgery places a healthy donor kidney in the body to take over much of the work of the failed kidneys. Long-term medicines are needed to reduce the risk of rejection.
- Conservative management: This approach focuses on controlling symptoms, managing complications, and maintaining quality of life without dialysis or transplantation.
Not everyone with reduced kidney function needs dialysis immediately. The decision depends on how well the kidneys are maintaining the body's balance, symptoms, blood test results, and overall health. Treatment options should be discussed with the kidney care team so that the benefits, limitations, and effect on daily life are understood.
Can kidney failure be prevented?
Not every case can be prevented, and some causes are outside a person's control. However, managing diabetes and high blood pressure, following recommended kidney testing, and seeking prompt care for serious illness may help protect kidney health. It is also important to have medicines reviewed when there are concerns about kidney function. Do not stop a prescribed medicine or change its dose without discussing this with the prescribing healthcare professional.
People who already have chronic kidney disease can work with their healthcare team to monitor kidney function, manage related conditions, and plan treatment before advanced kidney failure develops. Early recognition can help identify treatable causes and prepare for the care that may be needed later.