Chronic kidney disease, also sometimes called chronic renal failure, is a condition in which the kidneys work less well than normal.

The term “chronic” simply means that the condition has developed over a long period of time (usually over a number months or years) and has no implication in terms of the severity of the problem.

The major functions of the kidneys are to:

• Filter waste products from the body into the urine

• Regulate the salt and water content of the body

• Produce erythropoietin (epo) which promotes the formation of red blood cells

• Activate vitamin D, which is important for bone health

Therefore, patients with CKD are less able to remove waste products and excess fluid from the body, and may have anaemia and bone disease owing to the lack of epo and vitamin D, respectively. In severe cases the accumulation of waste products produces symptoms called uremia, which can only be alleviated by dialysis or kidney transplantation. This is known as end-stage kidney disease.

Who is at risk of CKD?

CKD is common and is found in approximately 14 per cent of the overall population of Bermuda, rising to more than 30 per cent of those over 65 years old. The risk of CKD is higher if you have other health problems. For example, CKD is found in nearly 40 per cent of people with diabetes, 35 per cent of people with cardiovascular disease and more than 20 per cent of people with high blood pressure.

Other risk factors for CKD include:

• Family history of kidney disease

• Black people and other ethnic minorities

• Obesity

• Smoking

• Older age

• Protein in the urine

• Autoimmune diseases such as lupus.

How do I know whether I have chronic kidney disease?

Most people with CKD have no symptoms and feel well. CKD can therefore only be identified from blood and urine tests. These may be done because you have a risk factor for CKD, but sometimes CKD is picked up by chance on tests done for other reasons.

Kidney function is reported as the “estimated glomerular filtration rate”. This is calculated using a formula that includes the blood creatinine level, age and sex. There is also a correction factor for racial background.

A normal eGFR is greater than 90 millilitres per minute and conventionally the severity of CKD is graded according to the eGFR:

• G1: normal or high — more than 90ml/min

• G2: mildly decreased — 60 to 89ml/min

• G3a: mildly to moderately decreased — 45-59ml/min

• G3b: moderately to severely decreased — 30-44ml/min

• G4: severely decreased — 15-29ml/min

• G5: renal failure — less than 15ml/min

Kidney problems can also result in abnormalities of the urine. Damaged kidneys can allow protein (albumin) and blood cells to leak from the blood into the urine. This can be initially identified using urine dipsticks and then followed up by laboratory measurement of the actual quantity of albumin in the urine. This is a good predictor of future loss of renal function. It is therefore also included in the CKD grading system:

• A1: normal to mildly increased — less than 30 milligrams of urine albumin per day

• A2: moderately increased — 30 to 300mg of urine albumin per day

• A3: severely increased — more than 300mg of urine albumin per day

The eGFR and urine albumin grades are then combined to help to predict future progression. For example, G2A1 — very low risk of progression, G3aA1 — moderate risk, G4A3 — very high risk.

Sometimes people do have symptoms that suggest an underlying kidney problem. These might include a change in the urine colour (red or brown), frothiness of the urine (suggestive of excess protein in the urine), changes in the quantity or frequency of passing urine (especially the need to pass urine overnight), swelling of the legs or face.

Symptoms of end-stage kidney disease — uremia — include loss of appetite, nausea, vomiting, altered sleep pattern, itching, change in higher mental function (such as loss of concentration, getting muddled more easily) and leg swelling.

What can happen if I have CKD?

Most people with CKD have no significant symptoms until the kidney function drops to an eGFR of less than 20ml/min.

Furthermore, for most people, the risk of developing end-stage kidney disease is very low. For example, if you have CKD G3, the risk of developing ESKD over a five-year period is about 1 per cent. For CKD G4, the risk is higher at about 19 per cent at five years.

A far more important problem associated with CKD is the development of cardiovascular disease such as angina, heart attacks, heart failure and stroke. Many more people with CKD will have problems related to CVD than will ever need dialysis or transplantation. For example, about 35 per cent of people with CKD will have symptomatic CVD, and about 30 per cent will have evidence of heart failure. The risks are even higher if you have CKD and diabetes.

Therefore, once CKD is identified, it is important to have treatment to reduce the risk of the kidney function getting worse and to protect the heart and blood vessels to prevent the development of CVD.

What can be done to treat CKD?

There are a number of treatment options available that have been shown to reduce the risk of progression of CKD and to help to prevent CVD.

• Identify the cause of CKD and have specific treatment if available — for example, immunosuppression for lupus kidney disease.

• Control the blood pressure. Aim for lower than 130/80mmHg.

• If proteinuria is present, use ACE inhibitors or angiotensin receptor blockers, and SGLT2 inhibitors.

• If diabetic, aim for good control of blood sugars. SGLT2 inhibitors and GLP-1 agonists can help to improve blood sugar control and have been shown to reduce the risk of progressive CKD.

• Statins. These reduce cholesterol levels and help to preserve kidney function and prevent CVD

• Low-dose aspirin.

• Stop smoking.

• Limit salt intake. Target should be less than 5g per day.

• Aim for an ideal body weight.

• Take regular exercise and eat a healthy balanced diet.

• Avoid drugs that can worsen kidney function — especially anti-inflammatory pain killers (NSAIDs).

Peter Topham is a consultant nephrologist at the Bermuda Hospitals Board. He is also co-editor of the textbook Oxford Desk Reference: Nephrology. The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician