Chronic Kidney Disease

Key points

What it is

Chronic kidney disease is a long-standing reduction in kidney function. The kidneys filter waste and excess fluid from the blood, balance salts and minerals, control blood pressure, and support red-blood-cell and bone health. In CKD this filtering capacity declines, usually gradually over years. It is graded on two measures: how well the kidneys filter (the eGFR, giving stages 1 to 5) and how much protein leaks into the urine (three categories). Together they predict the risk of problems ahead.¹

CKD is common, particularly with age and with diabetes and high blood pressure, and steps can be taken to reduce the risk of getting it and to slow it.²

What causes it, and who is at risk

The two commonest causes globally are diabetes and high blood pressure,³ both closely tied to metabolic health. Other causes include certain kidney and urinary diseases, recurrent infections or obstruction, some medications, and inherited conditions.² Risk factors therefore include diabetes, high blood pressure, cardiovascular disease, increasing age, family history, and certain ethnic backgrounds,^1,2 as well as obesity and insulin resistance.^4,5 Obesity is linked to a higher risk of kidney failure even after allowing for blood pressure and diabetes,⁴ and the metabolic syndrome (a large waist with raised blood pressure, raised triglycerides, low HDL cholesterol or raised fasting sugar) is linked to a higher risk of CKD.⁵ Many people have more than one risk factor.² NICE advises testing for CKD in people with diabetes, high blood pressure, a previous episode of acute kidney injury, cardiovascular disease or a family history of kidney failure, among others.¹

Symptoms and signs

Early CKD usually causes no symptoms and is found on testing,^2,3 though poor metabolic health can cause symptoms such as fatigue, difficulty losing weight, high blood pressure and skin tags. As CKD advances it can cause tiredness, swollen ankles, feet or hands, breathlessness, feeling sick, blood in the urine, poor appetite and weight loss, and passing urine more often at night.²

Because early disease is silent, testing those who are at risk of CKD is the key to catching it early.^1,2

How it is diagnosed

CKD is detected with two simple tests: a blood test estimating kidney filtering (the eGFR, where 90 or above is normal) and a urine test for protein (the albumin-to-creatinine ratio, or ACR). These are repeated to confirm that the change is persistent (over three months).³ Further tests may be done to look for other causes.² People with diabetes are advised to have both tests every year,³ and people with other risk factors are offered regular checks,^1,2 which helps with early detection.

The metabolic health perspective

The kidneys are highly vascular organs (many blood vessels), and they are damaged by the same processes that harm blood vessels elsewhere. High blood sugar injures the kidneys’ delicate filtering units over time (diabetic kidney disease), and high blood pressure, which so often goes with insulin resistance and obesity, adds mechanical strain.² Insulin resistance with persistently high insulin changes how the kidneys handle salt, raises pressure in the filters and promotes scarring.⁶ This is why CKD so often accompanies diabetes, high blood pressure and the wider pattern of poor metabolic health, and why metabolic health is one of the main levers for protecting the kidneys.

The main causes are largely modifiable. Good control of blood sugar and blood pressure, weight loss where relevant, and improving metabolic health slow the decline and reduce the chance of progression, and several modern medicines protect the kidneys directly.^1,2,3 Catching CKD early, before symptoms, gives the best chance of preserving function, and international guidance says finding CKD early in people at risk is likely to be beneficial.³

Treatment and management

The aims are to treat the underlying cause, slow progression, protect the heart (cardiovascular disease is one of the main causes of death in people with CKD²), and manage the consequences. The approach combines lifestyle change and sometimes medication, under medical care.

Lifestyle and the Health Foundations

Nutrition

Reducing sugar and ultra-processed foods will benefit most people, and international guidance advises eating fewer ultra-processed foods.³ In earlier CKD if there is also insulin resistance, the same principles that support metabolic health generally apply: build meals around sources of protein and non-starchy vegetables, with starchy carbohydrates reduced or personalised. This helps control blood sugar and blood pressure. The 28 Day Plan framework may be a helpful approach. In more severe CKD the approach changes. In CKD stages 3 to 5, international guidance suggests keeping protein at about 0.8 g per kg of body weight a day (a weak recommendation, based on low-certainty evidence),³ while NICE advises against low-protein diets.¹ A kidney (renal) dietitian can tailor protein, potassium, phosphate and salt.^1,3 Severe CKD is usually managed by kidney specialists.

Movement and weight

Aim for at least 150 minutes a week of moderate activity,^2,3 plus strength (resistance) exercise at least twice a week if able.² Regular activity and losing excess weight support blood pressure and metabolic health.

Blood pressure, smoking and alcohol

Controlling blood pressure, not smoking, and moderating alcohol all protect the kidneys.^1,2 NICE’s blood pressure targets are below 140/90, or below 130/80 when a lot of protein is leaking (an ACR of 70 mg/mmol or more).¹ Good sleep (seven to nine hours a night) supports healthy blood pressure and blood sugar, both relevant to kidney protection.

Other non-pharmaceutical options

People with CKD should be cautious with supplements, as some (and certain "natural" remedies) can harm the kidneys³ or accumulate to harmful levels. Correcting genuine deficiencies and avoiding substances that can damage the kidneys should be done under medical guidance. Always check supplements and over-the-counter medicines (including anti-inflammatory painkillers, which can harm the kidneys^1,2) with a pharmacist or clinician.

Medical and pharmaceutical treatments

• Blood-pressure medicines that also protect the kidneys (ACE inhibitors or ARBs) are often used, especially when protein is leaking into the urine, and in everyone with diabetes and a raised ACR.¹ Kidney function and potassium are checked before starting, one to two weeks after starting and after each dose increase.¹
• SGLT2 inhibitors (such as dapagliflozin or empagliflozin) protect the kidneys and heart. In two large trials they cut the risk of the kidneys getting much worse, or of death from heart or kidney causes, by between about a quarter and two-fifths, whether or not people had diabetes.^7,8 International guidance recommends them for many people with CKD, in particular those with a significant protein leak, heart failure or an eGFR under 45,³ and NICE recommends them as an add-on to an ACE inhibitor or ARB for people with an eGFR of 20 to under 45, or 45 to 90 with an ACR of 22.6 mg/mmol or more or type 2 diabetes.¹
• For people with type 2 diabetes and stage 3 or 4 CKD, finerenone, a newer medicine, can be added on top of these two if protein is still leaking (an ACR of 3 mg/mmol or more) and the eGFR is 25 or more.¹
• For people with diabetes, good blood-sugar control is a central part of protecting the kidneys.²
• In advanced (stage 5) disease, dialysis or a kidney transplant may eventually be needed.²

These decisions should be made with a clinician; the above is a summary for understanding, not prescribing guidance.

Complications and outlook

CKD raises the risk of cardiovascular disease, one of the main causes of death in people with CKD,² and advanced disease can lead to kidney failure requiring dialysis or transplant, as well as anaemia and bone problems.^1,3 The outlook depends heavily on the stage at which it is caught and on control of the causes: many people with early CKD never progress to serious disease, especially with good blood-sugar and blood-pressure control and modern kidney-protective medicines. Only around 2 in 100 people with CKD go on to kidney failure.²

When to see a doctor

• If you have diabetes, high blood pressure, or other risk factors, attend regular kidney checks (blood and urine tests).
• Check any new supplement or painkiller with a pharmacist (or clinician) if you have CKD, as some can harm the kidneys.

Summary