Kidney Failure

What the kidneys do

The kidneys filter about 180 liters of blood plasma a day, removing waste and excess fluid as urine. They also:

• balance sodium, potassium, calcium, phosphate and acid
• control blood pressure
• make erythropoietin, which signals the bone marrow to make red blood cells
• activate vitamin D for healthy bones

When they fail, all of these functions are affected.

Acute vs chronic kidney failure

See acute kidney injury and chronic kidney disease.

Less urine output and kidney failure

A drop in urine output (oliguria), generally less than about 400 ml (around 13.5 oz) a day in adults, is a key warning sign of acute kidney injury. It can come from:

• before the kidney (prerenal): dehydration, blood loss, heart failure, very low blood pressure, sepsis
• within the kidney: damage from medicines, toxins, severe infection, inflammation or muscle breakdown
• after the kidney (postrenal): blockage by an enlarged prostate, stones or tumors

Not everyone with kidney failure has low urine output. In chronic kidney disease, urine volume may stay normal until the late stages, even though waste is not being filtered well.

Symptoms

Early kidney disease rarely causes symptoms. As failure develops:

• reduced urine output, or urinating more at night
• swelling of the legs, ankles, face or hands
• tiredness and weakness, often from anemia
• poor appetite, nausea, vomiting and a metallic taste
• persistent itching
• muscle cramps and restless legs
• shortness of breath from fluid on the lungs
• trouble concentrating, confusion
• sleep problems
• high blood pressure that is hard to control
• in advanced uremia: chest pain from inflammation around the heart, twitching, and seizures

Causes

Chronic kidney failure

• Diabetes (diabetic nephropathy): the leading cause
• High blood pressure
• Glomerulonephritis: inflammation of the kidney filters, including IgA nephropathy and lupus nephritis
• Polycystic kidney disease
• Long-term urinary blockage and recurrent infections
• Long-term use of certain medicines, such as NSAIDs and lithium

Acute kidney injury

• severe dehydration, bleeding, sepsis or heart failure
• medicines: NSAIDs, some antibiotics, contrast dye, and combinations of ACE inhibitors or ARBs with diuretics during illness
• urinary blockage
• rhabdomyolysis (muscle breakdown)
• rapidly progressive glomerulonephritis

Diagnosis

• Blood tests: creatinine and eGFR, urea, potassium, bicarbonate, calcium, phosphate, hemoglobin
• Urine tests: albumin or protein, blood, and microscopy
• Urine output monitoring in hospital
• Kidney ultrasound: checks kidney size and blockage
• Kidney biopsy in some cases to identify the disease

Chronic kidney failure (stage 5) is defined as an eGFR below 15, or the need for dialysis.

Treatment

Acute kidney injury

• restore fluids and blood pressure
• stop harmful medicines
• relieve blockages, for example with a urinary catheter
• treat infection and the underlying cause
• manage high potassium and fluid overload
• temporary dialysis if needed

Many people recover partial or full kidney function within days to weeks, though some are left with chronic kidney disease.

Chronic kidney failure

Hemodialysis filters blood through a machine, usually 3 times a week for about 4 hours in a center, or more often at home. It needs access through a fistula in the arm or a catheter.

Peritoneal dialysis uses the lining of the belly as a filter. Fluid is put into the abdomen through a catheter and drained several times a day or overnight by a machine at home.

Kidney transplant offers the best survival and quality of life for suitable candidates. Kidneys can come from living or deceased donors. Lifelong immune-suppressing medicines are needed.

Conservative kidney management focuses on symptom control and quality of life without dialysis. It is a reasonable choice for some older or frail people.

Supporting treatments

• blood pressure control
• diet: limits on salt, potassium, phosphate and fluid as advised by a renal dietitian
• treatment of anemia with iron and erythropoiesis-stimulating agents
• phosphate binders and vitamin D for bone health
• adjusting medicine doses for reduced kidney function
• vaccinations, including hepatitis B

Complications

• hyperkalemia (high potassium), which can cause dangerous heart rhythms
• fluid overload and pulmonary edema
• anemia
• bone and mineral disorders
• heart disease, the leading cause of death in people with kidney failure
• infections
• uremic symptoms affecting the brain, nerves and skin

Outlook

Acute kidney injury often improves, but it raises the risk of later chronic disease. People with chronic kidney failure can live for many years on dialysis, and longer with a transplant. Early planning, ideally at stage 4, allows time for fistula creation, transplant evaluation and informed choices.

Prevention

• control blood sugar and blood pressure
• ask about kidney-protective medicines, such as ACE inhibitors, ARBs, SGLT2 inhibitors and finerenone, if you have diabetes or CKD
• avoid regular NSAID use if you have kidney disease
• stay hydrated during illness and heat
• get yearly kidney tests if you have diabetes, high blood pressure, heart disease or a family history

Frequently asked questions

What are the first signs of kidney failure?

Early signs often include less urine output or urinating more at night, swelling of the ankles or face, tiredness, nausea, poor appetite and itching. In chronic disease, many people have no symptoms until kidney function is very low, which is why blood and urine tests matter.

Does less urine output mean kidney failure?

Not always, but it can. Reduced urine is a key sign of acute kidney injury, often caused by dehydration, severe infection, medicines or blockage. It can also simply reflect not drinking enough. Sudden, marked reduction in urine with swelling or feeling unwell needs urgent care.

Can kidney failure be reversed?

Acute kidney injury often improves if the cause is treated quickly. Chronic kidney failure is usually permanent, but dialysis or a transplant can replace kidney function. Treating diabetes and blood pressure early can slow progression and prevent failure.

How long can you live with kidney failure?

It varies widely. Many people live 5 to 10 years or longer on dialysis, and some much longer. A kidney transplant usually offers longer survival. Without dialysis or transplant, survival is typically months, though conservative care can maintain comfort.

What is the difference between dialysis and a transplant?

Dialysis uses a machine or the belly lining to filter blood several times a week or daily. A transplant places a healthy donor kidney in the body, restoring kidney function but requiring lifelong anti-rejection medicines. Transplant generally offers better quality of life and survival.