Chronic Kidney Disease CKD

What is chronic kidney disease?

Chronic kidney disease (CKD) means that your kidneys are diseased or damaged in some way, or are ageing. As a result, your kidneys may not work as well as they used to. A range of conditions can cause chronic kidney disease (see later).

Chronic means ongoing, persistent and long-term. It does not mean severe as some people think. You can have a mild chronic disease. Many people have mild CKD.

Chronic kidney disease used to be called chronic renal failure but chronic kidney disease is a better term, as the word failure implies that the kidneys have totally stopped working. In most cases of chronic kidney disease this is not so. In most people who have chronic kidney disease there is only a mild or moderate drop in kidney function, which usually does not cause symptoms, and the kidneys have not 'failed'.

Acute kidney injury (AKI) occurs when the function of the kidneys is rapidly affected - over hours or days. For example, the kidneys may go into acute kidney injury if you have a serious blood infection which can affect the kidneys. This is in contrast to chronic kidney disease where the decline in function of the kidneys is very gradual - over months or years. See the separate leaflet called Acute Kidney Injury.

For more information, see the separate leaflet called What do kidneys do?

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• What do kidneys do?

How is chronic kidney disease diagnosed?

Kidney function is assessed using a combination of:

• A blood test called the estimated glomerular filtration rate (eGFR); and
• A measure of the amount of protein in the urine (proteinuria).

Increased protein in the urine and decreased eGFR are both associated with an increased risk of progressive chronic kidney disease.

Estimated glomerular filtration rate (eGFR)

A normal eGFR is 90 ml/minute/1.73 m or more. If some of the glomeruli do not filter as much as normal then the kidney is said to have reduced or impaired kidney function.

The eGFR test involves a blood test which measures a chemical called creatinine. Creatinine is a breakdown product of muscle. Creatinine is normally cleared from the blood by the kidneys. If your kidneys are not working very well and the glomeruli are not filtering as much blood as normal, the level of creatinine in the blood goes up.

The eGFR is calculated from your age, sex and blood creatinine level. An adjustment to the calculation is needed for people with African-Caribbean origin. See the separate leaflets called Routine Kidney Function Blood Test and Estimated Glomerular Filtration Rate (eGFR).

Proteinuria

Proteinuria means that your urine contains an abnormal amount of protein. Most proteins are too big to pass through the kidneys' filters and get into the urine. However, we all leak tiny amounts of a small protein called albumin into our urine.

If a kidney is damaged then increased amounts of albumin and other larger proteins from our blood can pass into the urine. This abnormal amount of protein in the urine is known as proteinuria. The amount of proteinuria is a good indicator of the extent of kidney damage. Proteinuria is also associated with an increased risk of the development of heart and blood vessel disease.

Proteinuria is usually first detected by a simple dipstick urine test. The amount of proteinuria is then usually measured by a sample of urine sent to the laboratory to measure the ratio of the level of either albumin or total protein in the urine compared with the amount of creatinine in the urine.

A lower level of excess protein in the urine is called microalbuminuria.

What are chronic kidney disease symptoms?

You are unlikely to feel unwell or have symptoms with mild-to-moderate chronic kidney disease - that is, stages 1 to 3. (However, there may be symptoms of an underlying condition such as kidney pain with certain kidney conditions.) Chronic kidney disease is usually diagnosed by the eGFR test before any symptoms develop.

Symptoms tend to develop when chronic kidney disease becomes severe (stage 4) or worse. The symptoms at first tend to be vague and nonspecific, such as feeling tired, having less energy than usual and just not feeling well. With more severe chronic kidney disease, symptoms that may develop include:

• Difficulty thinking clearly.
• A poor appetite.
• Weight loss.
• Dry, itchy skin.
• Muscle cramps.
• Fluid retention which causes swollen feet and ankles.
• Puffiness around the eyes.
• A need to pass urine more often than usual.
• Being pale due to anaemia.
• Feeling sick.

If the kidney function declines to stage 4 or 5 then various other problems may develop - for example, anaemia and an imbalance of calcium, phosphate and other chemicals in the bloodstream. These can cause various symptoms, such as tiredness due to anaemia, and bone thinning or fractures due to calcium and phosphate imbalance. End-stage kidney failure (stage 5) is eventually fatal unless treated.

What are the stages of chronic kidney disease?

Chronic kidney disease is diagnosed by the eGFR and other factors, and is divided into five stages:

Note: it is normal for your eGFR to change slightly from one measurement to the next. In some cases these changes may actually be large enough to move you from one stage of chronic kidney disease to another and then back again. However, as long as your eGFR is not getting progressively worse, it is the average value that is most important.

What if I have chronic kidney disease stage 3?

Stage 3 means moderate chronic kidney disease. This often means that you are unlikely to need to see a kidney specialist. However, your GP will need to see you regularly for monitoring, including blood and urine tests.

You may need treatments to reduce your risk of progressing to more severe chronic kidney disease. You will probably also need other treatments to reduce your risk of any other problems, particularly cardiovascular diseases (CVDs - see below).

However if regular blood and urine tests show that your chronic kidney disease is progressing to stage 4 then you will usually need to be referred to a kidney specialist to consider further assessments and treatment.

How common is chronic kidney disease?

About 1 in 10 people have some degree of chronic kidney disease. It can develop at any age and various conditions can lead to CKD. It becomes more common with increasing age and is more common in women.

Although about half of people aged 75 or more have some degree of chronic kidney disease, most of these people do not actually have diseases of their kidneys; they have normal ageing of their kidneys.

Most cases of CKD are mild or moderate (stages 1-3).

What causes chronic kidney disease?

A number of conditions can cause permanent damage to the kidneys and/or affect the function of the kidneys and lead to chronic kidney disease. Three common causes in the UK, which probably account for about three in four cases of chronic kidney disease in adults, are:

• Diabetes. Diabetic kidney disease is a common complication of diabetes.
• High blood pressure. Untreated or poorly treated high blood pressure is a major cause of CKD. However, CKD can also cause high blood pressure, as the kidney has a role in blood pressure regulation. About nine out of ten people with CKD stages 3-5 have high blood pressure.
• Ageing kidneys. There appears to be an age-related decline in kidney function. About half of people aged 75 or more have some degree of CKD. In most of these cases, the CKD does not progress beyond the moderate stage unless other problems of the kidney, such as diabetic kidney disease, develop.
• Certain medications, including non-steroidal anti-inflammatory drugs (if they are used long-term, especially at high doses); lithium, ciclosporin and tacrolimus. If you are taking one of these medicines, you should have a blood test to check your kidney function at least once a year.

Other less common conditions that can cause chronic kidney disease include:

• Diseases of the tiny filters in the kidneys (glomeruli), such as inflammation of the glomeruli (glomerulonephritis).
• Narrowing of the artery taking blood to the kidney (renal artery stenosis)
• Polycystic kidney disease. See the separate leaflet called Polycystic Kidney Disease.
• Blockages to the flow of urine, and repeated kidney infections.
• Previous injury to your kidney. If you have an acute kidney injury, you should be followed up for at least three years to check your kidney function.
• Having only one functioning kidney. Even though most people with a single kidney do not have any problems, your doctor will want to keep an eye on your kidney function.

However, this list is not complete and there are many other causes.

Do I need any further tests?

As mentioned, the eGFR test is done to diagnose and monitor the progression and severity of chronic kidney disease. For example, it should be done routinely at least once a year in people with stages 1 and 2 CKD, and more frequently in some people with stage 3 and in everyone with stage 4 or 5 CKD.

You are likely to have routine urine dipstick tests from time to time to check for blood and protein in the urine. Also, blood tests may be done from time to time to check on your blood level of chemicals such as sodium, potassium, calcium and phosphate. The need for other tests then depends on various factors and your doctor will advise. For example:

• An ultrasound scan of the kidneys or a kidney biopsy may be advised if certain kidney conditions are suspected. For example, if you have a lot of protein or blood in your urine, if you have pain that seems to be coming from a kidney, etc.
• A scan or having a sample taken (a biopsy) is not needed in most cases. This is because most people with chronic kidney disease have a known cause for the impaired kidney function, such as a complication of diabetes, high blood pressure or ageing.
• If the chronic kidney disease progresses to stage 3 or worse then various other tests may be done. For example, blood tests to check for anaemia and an altered level of parathyroid hormone (PTH). PTH is involved in the control of the blood level of calcium and phosphate.

What is the treatment for chronic kidney disease?

Treatment for most cases of chronic kidney disease is usually done by GPs. This is because most cases are mild-to-moderate (stages 1-3) and do not need any specialist treatment. Your GP may refer you to a specialist if you develop stage 4 or 5 CKD, or at any stage if you have problems or symptoms that need to be investigated by a specialist.

Research studies have shown that in many people, treatment at early stages of chronic kidney disease can prevent or slow down progression through to eventual kidney failure.

The aims of treatment include:

• If possible, to treat any underlying kidney condition.
• To prevent or slow down the progression of CKD.
• To reduce the risk of developing cardiovascular disease.
• To relieve symptoms and problems caused by CKD.

Treating any underlying kidney condition

There are various conditions that can cause CKD. For some of these there may be specific treatments for that particular condition - for example:

• Good blood sugar (glucose) control for people with diabetes.
• Blood pressure control for people with high blood pressure.
• Antibiotic medication for people with recurring kidney infections.
• Surgery for people with a blockage to urine flow.

Preventing or slowing down the progression of chronic kidney disease

There are ways to stop chronic kidney disease becoming any worse or to slow down any progression. You should have checks every now and then by your GP or practice nurse to monitor your kidney function - the eGFR test. They will also give you treatment and advice on how to prevent or slow down the progression of CKD. This usually includes:

• Blood pressure control. The most important treatment to prevent or delay the progression of chronic kidney disease, whatever the underlying cause, is to keep your blood pressure well controlled. Most people with CKD will require medication to control their blood pressure. Depending on the amount of albumin in your urine, your doctor may recommend a target blood pressure level to aim for of below 140/90 mm Hg or 130/80 mm Hg, and even lower in some circumstances. For children and young people with CKD and high levels of albumin in the urine, blood pressure should be kept less than average for their height.
• Review of your medication. Certain medicines can affect the kidneys as a side-effect which can make CKD worse. For example, if you have CKD you should not take anti-inflammatory medicines unless advised to by a doctor. You may also need to adjust the dose of certain medicines that you may take if your CKD gets worse.
• Diet. if you have more advanced CKD (stage 4 or 5) then you will need to follow a special diet. See the separate leaflet called Diet in Chronic Kidney Disease.

Medication to protect your kidneys

• ACE inhibitors and ARBs. If you have high levels of protein in your urine then you may be advised to take medication even if your blood pressure is normal. Two related types of medication have been shown to be beneficial for many people with CKD. This is because they can prevent further worsening of the function of your kidneys. These medicines are called:
• Angiotensin-converting enzyme (ACE) inhibitors (for example, captopril, enalapril, ramipril, lisinopril); and
• Angiotensin receptor blockers (ARBs), such as losartan, valsartan, candesartan, telmisartan).
• SGLT2 inhibitors. A group of medicines called the SGLT2 inhibitors (such as canagliflozin, dapagliflozin, empagliflozin and ertugliflozin) were originally used to keep blood sugar under control in type 2 diabetes. However, more recent studies show that some of them can significantly reduce decline in kidney function. These may be recommended whether you have type 2 diabetes or not. The National Institute for Health and Care Excellence (NICE) has issued new guidance recommending that they should be offered to, or considered for, most people with type 2 diabetes and CKD.

Treating end-stage kidney failure

Only a small number of people with chronic kidney disease progress to end-stage kidney failure (stage 5 CKD) that requires kidney dialysis or kidney transplant. If you reach stage 4 or 5 CKD, you are likely to be referred to a specialist in kidney disease at the hospital.

You will need to attend regularly for follow-up - how often depends on how much your kidney function is affected and how stable your results are. As well as monitoring your kidney function, your team is likely to carry out certain blood tests:

• Full blood count (for anaemia).
• Calcium.
• Phosphate.
• Vitamin D.
• Parathyroid hormone.

The options for treatment include:

• Haemodialysis - your blood is removed from a vein in your arm, filtered to remove waste products and returned through another tube.
• Peritoneal dialysis - a thin tube is inserted into your stomach near your tummy button. Fluid is pumped into your stomach cavity to filter waste products, and drained into a bag.
• Kidney transplant.

NICE says that patients receiving dialysis should be offered the choice of having their treatment at home or in a hospital or clinic. It advises that patients, in discussion with doctors, should be able to decide which type of dialysis is right for them and where they will receive it, depending on local arrangements.

Reducing the risk of developing cardiovascular diseases

People with chronic kidney disease have an increased risk of developing CVDs, such as heart disease, stroke, and peripheral arterial disease. People with CKD are actually twenty times more likely to die from cardiovascular-related problems than from kidney failure. This is why reducing any other cardiovascular risk factors is so important. See the separate leaflet called Cardiovascular Disease (Atheroma).

This typically includes:

• Good control of blood pressure.
• Good control of blood glucose level if you have diabetes.
• Medication to lower your cholesterol level (called statins), which is often given to people with CKD.
• Where relevant, to tackle lifestyle risk factors. This means to:
  • Stop smoking if you smoke and cut back if you drink a lot of alcohol.
  • Eat a healthy diet which includes a low salt intake.
  • Keep your weight and waist in check.
  • Take regular physical activity.

Relieving symptoms and problems caused by chronic kidney disease

If chronic kidney disease becomes severe you may need treatment to combat various problems caused by the poor kidney function. For example:

• Anaemia may develop which may need treatment with iron or erythropoietin - a hormone normally made by the kidneys.

• Abnormal levels of calcium or phosphate in the blood may need treatment.
• You may be advised about how much fluid to drink, and how much salt to take.
• Other dietary advice may be given which can help to control factors such as the level of calcium and potassium in your body.

If end-stage kidney failure develops, you are likely to need kidney dialysis or a kidney transplant to survive.

People with stage 3 CKD or worse should be immunised against influenza each year, and have a one-off immunisation against pneumococcus. People with stage 4 CKD should be immunised against hepatitis B.

What is the outlook for chronic kidney disease?

Stages 1-3 chronic kidney disease (mild-to-moderate) are common, with most cases occurring in older people. It tends to become gradually worse over months or years. However, the rate of progression varies from case to case, and often depends on the severity of any underlying condition. For example, some kidney conditions may cause your kidney function to become worse relatively quickly. However, in most cases, chronic kidney disease progresses only very slowly.

For many people with CKD there is a much higher risk of developing serious CVD than of developing end-stage kidney failure.

In short, the following can make a big difference to your outlook (prognosis):

• Attention to blood pressure control.
• Careful review of medications to make sure that the only ones used are those which put least strain on kidneys.
• Tackling factors that reduce your risk of developing CVDs.