Kidney Disease

What your kidneys do

Each kidney contains about a million tiny filters called nephrons. Together they:

• remove waste products and extra fluid as urine
• balance salt, potassium, acid and other minerals
• help control blood pressure
• make a hormone (erythropoietin) that stimulates red blood cell production
• activate vitamin D for healthy bones

When kidney function falls, waste and fluid build up, and these other jobs suffer too.

Acute vs chronic kidney disease

Stages of chronic kidney disease

CKD is staged by the estimated glomerular filtration rate (eGFR), a measure of filtering ability calculated from a blood creatinine test, and by the amount of albumin (a protein) in the urine.

Urine albumin is graded as A1 (below 30 mg/g), A2 (30 to 300 mg/g) and A3 (above 300 mg/g). Higher albumin means a higher risk of progression and heart disease.

Early signs and symptoms

Most people have no symptoms in stages 1 to 3. As kidney function falls further, symptoms may include:

• swelling (edema) of the ankles, feet, hands or around the eyes
• foamy or bubbly urine, a sign of protein
• needing to urinate more often, especially at night, or passing less urine
• tiredness, weakness and difficulty concentrating
• poor appetite, nausea and a metallic taste
• itchy, dry skin
• muscle cramps
• shortness of breath from fluid buildup
• trouble sleeping
• high blood pressure that is hard to control

Causes and risk factors

• diabetes: the leading cause. See diabetic kidney disease
• high blood pressure: both a cause and a consequence of kidney disease
• glomerulonephritis: inflammation of the kidney filters, from immune conditions such as IgA nephropathy and lupus
• polycystic kidney disease: an inherited condition causing many cysts
• repeated kidney infections, kidney stones or long-standing urinary blockage, such as an enlarged prostate
• long-term use of NSAIDs and some other medicines
• heart disease, obesity and smoking
• family history of kidney failure
• age over 60
• Black, Hispanic, American Indian and Alaska Native people have higher rates of kidney failure

Diagnosis

• Blood test: creatinine to calculate eGFR.
• Urine test: urine albumin-to-creatinine ratio (uACR). Both tests are needed, because damage can show in one before the other.
• Repeat testing: CKD is confirmed when abnormalities persist for more than 3 months.
• Blood pressure measurement.
• Ultrasound of the kidneys to look at size, cysts, stones and blockage.
• Kidney biopsy in selected cases, to identify glomerulonephritis and other specific diseases.

Treatment

Slowing progression

• Control blood pressure, usually aiming for a systolic below about 120 to 130 mmHg as advised by your doctor.
• ACE inhibitors or ARBs: lower blood pressure and protect the kidneys, especially when there is protein in the urine.
• SGLT2 inhibitors (such as dapagliflozin or empagliflozin): slow kidney decline in people with and without diabetes.
• Blood sugar control in diabetes. Some diabetes medicines, such as GLP-1 receptor agonists and finerenone, also protect the kidneys in diabetic kidney disease.
• Statins to lower heart disease risk, which is high in CKD.
• Avoid NSAIDs such as ibuprofen and naproxen, and check every new medicine and supplement with your doctor or pharmacist.
• Quit smoking, stay active and maintain a healthy weight.

Diet

A kidney dietitian can tailor advice, which often includes:

• limiting salt to help blood pressure and swelling
• moderating protein in later stages
• limiting potassium or phosphorus if blood levels are high
• adjusting fluids in advanced disease

Treating complications

• anemia: iron and erythropoiesis-stimulating medicines
• bone and mineral problems: phosphate binders and activated vitamin D
• acid buildup: sodium bicarbonate
• fluid overload: diuretics

Kidney failure (stage 5)

• Dialysis: hemodialysis, usually 3 times a week at a center or at home, or peritoneal dialysis done daily at home.
• Kidney transplant: the best long-term option for many people, from a living or deceased donor.
• Conservative kidney management: focusing on symptom control and quality of life without dialysis, chosen by some older or frail people.

Complications

• heart disease and stroke, the leading causes of death in people with CKD
• high potassium, which can cause dangerous heart rhythms
• anemia
• bone disease
• fluid overload
• kidney failure

Prevention

• control blood pressure and blood sugar
• get yearly kidney tests if you are at risk
• avoid regular NSAID use
• stay hydrated, especially during illness
• treat urinary infections promptly
• do not smoke, and limit alcohol

Frequently asked questions

What are the early signs of kidney disease?

Early kidney disease usually has no symptoms. When signs appear, they can include foamy urine, swelling of the ankles or around the eyes, needing to urinate at night, tiredness and high blood pressure. Blood and urine tests are the only reliable way to detect it early.

What causes kidney disease?

Diabetes and high blood pressure cause most chronic kidney disease. Other causes include glomerulonephritis, polycystic kidney disease, repeated kidney infections or stones, urinary blockages and long-term use of some medicines such as NSAIDs.

Can kidney disease be reversed?

Acute kidney injury is often reversible if treated promptly. Chronic kidney disease usually cannot be reversed, but its progression can often be slowed or stopped with blood pressure and blood sugar control and kidney-protective medicines.

What are the stages of kidney disease?

Chronic kidney disease has five stages based on eGFR, from stage 1 (normal filtering with signs of damage) to stage 5 (kidney failure, eGFR below 15). Doctors also grade the amount of protein in the urine to estimate risk.

What is a normal eGFR?

An eGFR of 90 or above is normal for most young adults, and it declines slowly with age. An eGFR below 60 for more than 3 months indicates chronic kidney disease. Your doctor interprets eGFR together with urine protein and other factors.