Chronic Kidney Disease - CKD
What do your kidneys do?
Your kidneys are two bean-shaped organs, about the size of your fist, that lie on either side of your body. Their main function is to remove waste products from the blood and convert them into urine. Your kidneys also have a number of other important functions such as maintaining blood pressure, regulating the concentrations of salts and the pH in the blood, producing the active form of vitamin D that is needed for good bone health and a hormone called erythropoetiein that tells your body to make red blood cells.
What is CKD?
CKD is a medical term that describes the inability of the kidney to carry out these functions as normal. The chronic refers to it being a long standing condition rather than severity. The damage to the kidneys is most often caused by other medical conditions. The most common ones are diabetes and high blood pressure. Moderate to severe CKD is also associated with an increased risk of other significant adverse outcomes such as acute kidney injury, falls, frailty and mortality. The risk of developing CKD increases with age and CKD progresses to end-stage kidney disease in a small but significant percentage of people.
How common is CKD?
In the UK it is estimated that around 1 in 10 of the population may have CKD, but it is less common in young adults. About 20%-25% of men and women between the ages of 65 and 74 have some degree of CKD. It is important to note that many of the elderly people with CKD may not have ‘diseased’ kidneys, but have normal ageing of their kidneys.
How is CKD identified?
You don’t usually have any symptoms with CKD and so it is identified with blood tests. Detecting it early is vital as there is evidence that treatments can prevent or delay its progression and can reduce or prevent the development of complications. The tests for CKD are simple and freely available. To assess how well your kidneys are working your glomerular filtration rate (GFR) is measured. The GFR describes how efficiently your blood is filtered by the kidney. Your GFR is a measurement of how many millilitres (mL) of waste fluid your kidneys can filter from the blood in a minute (measured in mL/min). A healthy pair of kidneys should be able to filter more than 90mL/min.
We usually estimate the GFR using a formula rather than being measured directly (the result is called the estimated GFR or eGFR). This involves taking a blood sample to measure the levels of a muscle waste product, called creatinine, alongside taking into account your age, gender and ethnic group. The result can be thought of as the percentage of normal kidney function you have remaining. For example an eGFR of 50mL/min is about 50% kidney function.
Your urine is also usually tested, as part of identifying CKD, to ensure that there is no protein (termed proteinuria) or blood (haematuria) in your urine. If there is protein present, the amount that is leaking is quantified using either an albumin:creatinine ratio (ACR) or protein:creatinine ratio (PCR). This result is used in combination with your eGFR to give an accurate idea of how well the kidneys are functioning.
Are there different stages of CKD?
There are six stages of CKD based on the eGFR result. The higher the stage, the more severe the CKD is and the more often you need to have kidney function tests performed. A diagnosis of CKD is usually only confirmed if repeated eGFR tests show your eGFR is consistently lower than normal over three months.
Stage 1 and 2 are the mildest forms and patients often need no more than annual blood tests
Stage 1 (G1) – the eGFR is normal (>90mL/min) but there is evidence of kidney damage present
Stage 2 (G2) – the eGFR is slightly decresased (60-90mL/min) with evidence of kidney damage present
Stage 3 is split into stages a and b and refers to a reduction of eGFR to below 60 mL/min with or without evidence of kidney damage
Stage 3a (G3a) – mild-moderate reduction (eGFR 45-59 mL/min) requiring annual checks of your eGFR
Stage 3b (G3b) – moderate-severe reduction (eGFR 30-45 mL/min) requiring six monthly checks of your eGFR
In Stage 4 (G4), the eGFR is severely reduced (15-29 mL/min). By this time, people often experience symptoms of CKD and it requires further testing, at least every six months, and sometimes more frequently.
By Stage five (G5): the kidneys have lost almost all of their function (an eGFR below 15 mL/min), which is known as established renal failure. Further testing should be carried out at least every three months.
Who should be screened for CKD?
A number of different groups of patients should be screened for CKD. These include people who are prescribed drugs that can damage the kidneys such as calcineurin inhibitors (e.g. cyclosporin or tacrolimus), lithium and non-steroidal anti-inflammatory drugs (NSAIDs). Testing should also be offered to patients with risk factors for CKD such as:
Acute kidney injury
Cardiovascular disease (ischaemic heart disease, chronic heart failure, peripheral vascular disease or cerebral vascular disease)
Structural renal tract disease, recurrent renal calculi or prostatic hypertrophy
Multisystem diseases with potential kidney involvement – for example, systemic lupus erythematosus
People with a family history of end-stage kidney disease or hereditary kidney disease
Following opportunistic detection of haematuria
What are the symptoms of CKD?
Most people with CKD have no symptoms because the body is able to cope with even a large reduction in kidney function. If the kidneys continue to lose function and there is progression towards kidney failure this will usually be tracked by blood tests and monitoring. The symptoms are often quite nonspecific and can be caused by many less serious conditions. They include:
Weight loss and poor appetite
Swollen ankles, feet or hands (due to water retention)
Shortness of breath
An increased need to urinate, particularly at night
Erectile dysfunction in men (an inability to get or maintain an erection)
How is CKD treated?
There is no cure for chronic kidney disease, although treatments 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. The main way to reduce the chances of CKD developing is to ensure any existing conditions, such as diabetes and high blood pressure, are carefully managed. Some lifestyle changes can also reduce the risk of CKD developing such as having a healthy diet, avoiding drinking excessive amounts of alcohol, exercising regularly and avoiding medicines that can damage the kidney.
When should I see a specialist?
Most cases of CKD can be managed by a patient’s own GP but kidney specialists become involved when the disease is more advanced, other abnormal features are present or simply when advice is needed to help the GP manage the condition in the longer term. Kidney specialists aim to sustain useful kidney function for as long as possible.
Recommendations for when to refer to a kidney specialist can be found here: