Disease of the Month: Chronic kidney disease (CKD)

Chronic kidney disease (CKD) is a long-term condition where the kidneys do not work effectively. This is due to damage, disease or just simple ageing.

Recent research suggests that one in 10 of the population may have CKD, but this is mainly in the elderly. The disease is much less common in young adults, being present in one in 50 people. For the older population, those aged over 75 years, CKD is present in one out of two people.

It must be noted that many of the elderly people with CKD may not have diseased' kidneys, but have normal ageing of their kidneys. Although severe kidney failure will not occur with normal ageing of the kidneys, there is an increased chance of high blood pressure, heart disease or stroke.

What causes chronic kidney disease (CKD)?

A number of conditions can cause permanent damage to the kidneys and affect their functioning, leading to CKD. The three most common causes in the UK, which probably account for about three in four cases of CKD in adults, are:

 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.

 Diabetes. Diabetic kidney disease (diabetic nephropathy) is a common complication of diabetes. In this condition the filters of the kidneys, the glomeruli, become damaged. Because of this the kidneys 'leak' abnormal amounts of protein from the blood into the urine. A raised level of albumin in the urine is typically the first sign that the kidneys have become damaged by diabetes.

 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 develop, such as diabetic kidney disease.

Other less common conditions that can cause CKD include:
• Blockages to the flow of urine, and repeated kidney infections.
• Diseases of the glomeruli, such as inflammation (glomerulonephritis).
• Polycystic kidney disease.
• Narrowing of the artery taking blood to the kidney (renal artery stenosis)

How is CKD diagnosed?

A simple blood test can estimate the volume of blood that is filtered by the glomeruli in the kidneys over a given period of time. This test is called the 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 and is normally cleared from the blood by the kidneys. If the kidneys are not working affectively 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 gender, age and blood creatinine level. An adjustment to the calculation is needed for people with African-Caribbean origin (due to proportionally greater muscle mass).

CKD is diagnosed by the eGFR and other factors, and is divided into the following five stages; 

• CKD stage 1 is eGFR greater than 90 mls/min, with some sign of kidney damage on other tests (if all the other kidney tests are normal, there is no CKD).
• CKD stage 2 is eGFR 60-90 with some sign of kidney damage (if all the kidney tests are normal, there is no CKD).
• CKD stage 3a is eGFR 45-59 ml/min, a moderate reduction in kidney function
• CKD stage 3b is eGFR 30-44 ml/min, a moderate reduction in kidney function
• CKD stage 4 is eGFR 15-29 ml/min, a severe reduction in kidney function
• CKD stage 5 is eGFR less than 15 ml/min, established kidney failure, when dialysis or a kidney transplant may be needed.

Symptoms

You are unlikely to feel unwell or have symptoms with mild-to-moderate CKD (stages 1 to 3) because the body is capable of tolerating a large reduction in kidney function. CKD is usually diagnosed by the eGFR test before any symptoms develop.

Symptoms tend to develop when CKD 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 CKD, the following symptoms may develop:

• Raised blood pressure
• Fluid retention which causes swollen feet and ankles.
• Difficulty thinking clearly.
• A poor appetite.
• Weight loss.
• Muscle cramps.
• Puffiness around the eyes.
• Dry, itchy skin.
• A need to pass urine more often than usual.
• Being pale due to anaemia.
• Darkness or redness in the urine
• Frequent urination, sometimes with pain or burning on passing urine
• Persistent thirst
• Back pain in the renal area, especially if there is fever
• Tiredness or feeling unwell without apparent cause
• Widespread itchy skin (pruritus)

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 many 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.

Treating chronic kidney disease

There is no cure for CKD, although treatment can slow or halt the progression of the disease and can prevent other serious conditions developing. People with CKD are known to have an increased risk of a heart attack because of changes that occur to the circulation.

In general, treatment consists of measures to help control signs and symptoms, reduce complications, and slow progression of the disease. If the kidneys become severely damaged, treatment will be required for end-stage kidney disease.
Research studies have shown that, in many people, treatment at early stages of CKD 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
In a minority of people, CKD may cause kidney failure, also known as established renal failure (ERF) or end-stage kidney disease. In this situation, the usual functions of the kidney stop working.
To survive, people with ERF may need to have artificial kidney treatment, called dialysis, or a kidney transplant.

What is the outlook (prognosis)?

Stages 1-3 CKD (mild-to-moderate) are common, with most cases occurring in older people. It tends to become gradually worse over time.

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 the kidney function to become worse relatively quickly.

However, in most cases, CKD progresses only very slowly. Only a small number of people with CKD progress to end-stage kidney failure (stage 5 CKD) that requires kidney dialysis or kidney transplant.

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

Underwriting considerations

The underwriter will require full details of the medical history, including latest renal function tests and eGFR. This will help establish the staging of the CKD. Details of any complications would also need to be established before the underwriter could consider a final decision.

Final terms will depend on the person's age, the actual staging of the CKD and whether or not there are any complications, such as diabetic nephropathy or cardio vascular disease.

Fergus Bescoby is underwriting development manager at VitalityLife