Understanding the stages of chronic kidney disease (CKD)
Written in association with:What exactly is chronic kidney disease, how severe is it, and can it be cured? We asked leading London nephrologist Dr David Game what it means for kidney disease to be chronic, and what the different stages mean:
What is chronic kidney disease?
Chronic kidney disease (CKD) is a long-term reduction in kidney function.
Let us first explore what we mean by kidney function. The kidneys work by filtering out harmful substances from our blood. Kidney function is assessed by measuring what we call the glomerular filtration rate (GFR).
The glomerular filtration rate can be found by checking the levels of certain substances in your blood, including creatinine. By looking at these levels and running some calculations, we can estimate your glomerular filtration rate and therefore how well your kidneys are working. In rare cases, chronic kidney disease can occur even with a normal glomerular filtration rate.
Most cases of chronic kidney disease are mild and are only detected in these types of blood tests. The term chronic simply means that your kidneys have had problems functioning for a long time.
What causes chronic kidney disease?
The most common causes of chronic kidney disease in the UK are high blood pressure and diabetes. In addition, chronic kidney disease can itself be a cause of high blood pressure.
Less common causes include:
- Kidney inflammation (nephritis)
- Vascular disease
- Polycystic kidneys
- Urinary retention
- Recurrent infections
- Recurrent kidney stones
- Certain medications
How does chronic kidney disease affect the body?
Although most cases of chronic kidney disease present no symptoms, it can have knock on effects. The failure to remove harmful products from your body can combine with high blood pressure and cholesterol to cause disease of the blood vessels. This can increase your risk of life-threatening problems such as heart attack and stroke.
Treatment for most chronic kidney disease therefore involves trying to bring these risk factors under control.
What are the stages of chronic kidney disease?
Chronic kidney disease is classified into five stages, with stage 1 being the mildest and 5 the most severe. The stages are generally classified on the basis of your estimated glomerular filtration rate, or eGFR:
- stage 1 – a normal eGFR (above 90ml/min), but other tests have detected signs of kidney damage
- stage 2 – a slightly reduced eGFR (60-89ml/min), with other signs of kidney damage
- stage 3a – an eGFR of 45-59ml/min
- stage 3b – an eGFR of 30-44ml/min
- stage 4 – an eGFR of 15-29ml/min
- stage 5 – an eGFR below 15ml/min, meaning the kidneys have lost almost all of their function
The eGFR roughly approximates to kidney function, meaning an eGFR reading of 30ml/min would translate to around 30% kidney function.
What does this means in terms of severity? It’s possible to live normally with kidneys that are functioning at well below their original capacity, and you may not even notice any symptoms.
In CKD 4, other functions of the kidney may be affected such as maintaining bone health and preventing anaemia: these are managed by a nephrologist.
Only if you have kidney functioning at around 8% (sometimes 10% in diabetics) or below will you require dialysis treatment. It is unusual to need dialysis if your kidney function is higher.
Can chronic kidney disease be cured?
Chronic kidney disease cannot really be cured, but in most cases it can be stabilised. Your nephrologist will work with you to try and make sure that your kidneys are working sufficiently for as long as possible. This involves watching any risk factors closely and avoiding further kidney damage.
In later stages (CKD 4 and 5), a nephrologist will discuss dialysis or kidney transplantation. In most cases transplantation is better because it can restore your kidney function to near-normal whereas dialysis only cleans the blood and removes fluid: both are major interventions.
