A-Z

Kidney health

How and why is kidney function monitored?

People with long term conditions such as diabetes or cardiovascular disease, a history of kidney problems, or a family history of severe kidney disease should already be having their kidney function checked routinely. All other adults aged over 40 should now be invited for a 5-yearly NHS Health Check and may be considered for kidney function tests as part of that. It is NHS policy that all adults over 40 who are at an increased risk of developing kidney problems should be having their kidney function checked. 

How is kidney function measured?

Kidney performance is measured using a simple blood test in combination with a urine test. The level of a waste product in the blood called creatinine is converted into a measure of how efficiently the kidneys are filtering the blood; this is called the estimated glomerular filtration rate (eGFR). The conversion formula takes into account the patient’s age, sex, and ethnicity, as well as the creatinine itself. An eGFR of 90 -100mls per minute is normal, so you may find it convenient to think of this as being 100% efficient, while an eGFR of 50 means the kidneys are working at 50% efficiency, in other words, half as well as they should. An eGFR above 60 accompanied by raised levels of protein in the urine represents chronic kidney disease stages 1 – 2. An eGFR of between 59 and 30 regardless of the level of protein in the urine equates to stage 3 chronic kidney disease. An eGFR below 30, or a sustained decrease in eGFR of 25% or more, should trigger the GP to consider referral to a hospital specialist.

Stages of Chronic Kidney Disease (CKD)
 

Dr Kathryn Griffith explains how doctors measure people’s kidney function by testing for the build-up of waste products in the blood and leakage of protein into the urine.

Dr Kathryn Griffith explains how doctors measure people’s kidney function by testing for the build-up of waste products in the blood and leakage of protein into the urine.

SHOW TEXT VERSION
PRINT TRANSCRIPT
We have a special blood test that we use to assess kidney function, and that measures a waste product in the bloodstream, and it uses a formula to calculate how efficient your kidneys are working. And if the efficiency of the kidneys drops below 60%, in other words if that number - which we call glomerular filtration rate - if that drops below 60% and that has been present for over 3 months, then we think that a patient may have got chronic kidney disease.

So people wonder why we ask to test the urine when you have got chronic kidney disease, and that’s because testing the urine helps us to look at kidney function in a different way. So I’ve explained at the start that often we pick up chronic kidney disease by doing a blood test where we look for the waste product called creatinine, and you look at the level changing and rising as the kidneys work less efficiently. But we can also look at the efficiency of the kidneys working as a filter. Now the kidneys are remarkably clever. They filter our blood. They keep inside the blood stream all the things we want to keep in, and they allow out the waste products and metabolised drugs, and other things that we actually want to get rid of. And the idea is there is a membrane between the two layers which keeps the things we want to keep in and allows the other things to get out.

Now there are processes that can damage that membrane so it allows things to get out into the urine that wouldn’t normally be there. And the thing we look for particularly is a small protein called albumin, and that detects very small amounts of damage to that membrane and we can pick up very readily on a urine test the amount of albumin in the urine. Over time many of our patients with CKD will get albumin in the urine, but there is a particular group of people where albumin occurs early. So if you have got diabetes, the first sign of damage to the kidneys isn’t on the blood test - so the creatinine level may be normal - but we see leakage through the kidneys into the urine of albumin.

So for people with diabetes for many years, we have been actually asking them to produce urine samples on at least a yearly basis because this is the early warning sign of kidney damage in someone with diabetes. We also know that there are people with hypertension, high blood pressure and other conditions who will also start to leak albumin in the urine, and these people need extra special blood pressure control because we know that by treating blood pressure better we can reduce the strain on the kidneys and we can reduce the albumin going through into the urine. So it’s a very, very useful test. It’s not always a test that patients like to do, because people forget, but it is really important. It is as or even more important for some people than doing the blood test. And every year we would like to see our patients, we do blood tests, we do urine tests and obviously we check their blood pressure.
 
The eGFR is only an estimate; it varies between tests and can go up as well as down. It is possible to have an isolated low eGFR test result due to an episode of illness, a change in medications that can affect kidney function, or a technical problem at the laboratory, in which case the test will be repeated.

Graph showing an example of the eGFR declining then stabilising over time
 

How often should kidney function be monitored?

People found to have a mild to moderate decline in kidney performance (CKD stages 1 – 3) on repeated tests over a three month period should be monitored by their GP through regular blood tests to check whether the eGFR remains stable or is getting lower; a urine sample should also be taken to check for protein. The frequency of monitoring recommended by NICE (National Institute for Health Care Excellence) varies between once a year to two or more times a year depending on: the stage of CKD and level of protein in the urine, past patterns of the eGFR and creatinine levels, the underlying cause of the CKD, other illnesses and long term conditions present, and the patient’s wishes.
 

Dr Kathryn Griffith explains how often people with early stage chronic kidney disease should be monitored and how she communicates the test results.

Dr Kathryn Griffith explains how often people with early stage chronic kidney disease should be monitored and how she communicates the test results.

SHOW TEXT VERSION
PRINT TRANSCRIPT
So [pause] for many of our patients chronic kidney disease is not a single condition. It is part of other medical problems they have. So we might pick it up in someone who has already had a heart attack, in someone whose has had high blood pressure and someone with diabetes. We don’t need to do separate check-ups for chronic kidney disease on top of everything else. So ideally it should be possible for a patient to come to the practice and been seen about their medical problems as a whole rather than just focusing on one aspect. So perhaps as part of your blood pressure check you will be asked to have your blood pressure measured, you’ll have a blood test, we might also send your urine off to check your kidney function.

After you have had the test done then usually in my practice I would ask patients to contact the practice to see if I have left them a message about the results. Often the kidney function will be gradually declining. That is not necessarily anything to worry about. It’s the rate it is declining and the level it is at that matter. So I will perhaps leave them a message to say, ‘Your kidney function is the same as before, so it is not normal but it is what it was for you and it’s not getting worse.’ I might say, ‘The kidney function is a little worse’, but that would, in many ways what I would expect as people get older. Sometimes I ask people to come back and see me to talk about it because it’s often very difficult on the telephone to get over these concepts and to understand the exact level. I can also print them off a graph. I can show them what’s actually been happening to their kidney function so that I think it’s important that you, visual images are very good to help you to see what’s happening. But I would expect the graph to show a small decline. Sometimes it will actually show things going up and down because kidney function can improve a little and it can decline a little. So it’s not a smooth graph. It would be moving up and down, and again that’s what I would expect and wouldn’t be anything to worry about.

So most of my patients I would see perhaps once or twice a year about their kidney function, unless their kidney function is in the lower levels. And when it drops below 30 we call that chronic kidney disease Stage 4, and those people would have more check-ups and would perhaps be expected to go to the hospital.

The people with kidney function between 30 and 60 I would expect can be managed most of the time by a GP and a practice nurse within a practice as part of the practice chronic disease management programme and with regular check-ups there. So there aren’t any specific issues other than the things that we do anyway, which is about treating blood pressure and about lowering risk of heart disease, and about lifestyle advice, all of these things we should be able to manage quite usefully in Primary Care.
 
Doctors disagree about whether to tell patients if they have signs that their kidneys are not working as well as they used to. Some think that patients need to be aware of this so that they can take steps to stay as healthy as possible (see ‘Why is kidney health important?’). Others are reluctant to tell patients they have early stage kidney disease or impairment because they feel it could cause unnecessary anxiety, particularly in those patients who have other health problems that are impacting on their life and whose blood pressure is already controlled and have been given healthy lifestyle advice for other reasons. (See also ‘When should doctors inform people of a mild kidney impairment?’)
 

Dr Kathryn Griffith believes it is important for most patients to know about their early stage chronic kidney disease, and explains how she tells her patients about it.

Dr Kathryn Griffith believes it is important for most patients to know about their early stage chronic kidney disease, and explains how she tells her patients about it.

SHOW TEXT VERSION
PRINT TRANSCRIPT
I have to say that I would inform a patient if I feel that it is important for them to know. So my very elderly patients I may not necessarily tell them, but then of course they are the ones also who are at issue, who are at risk of acute kidney injury. But there are some patients who, who may not benefit from knowing, but for the majority of patients they will benefit from knowing and having that information.

We only have very short consultations in general practice. It’s often very difficult to cram it in, and sometimes people feel afraid or anxious about telling a piece of information that they feel is going to open up a whole catalogue of questions and information. So what I think, this is where I think patient information is so important. So I would like to be able to say to someone that, ‘We’ve have had a blood test. It does show that you have got chronic kidney disease, which means that you’ve had several blood tests over a period of time which show that your kidney function has declined’. I would like to give them a simple explanation but also an information leaflet that they can take home with them, and then what I do is I print things off the computer and get people to come back, because they can’t take everything in and it, sometimes it is a bit of a shock and it is worrying, but I think if you can give them the information to read about, invite them to come back, then you’re answering questions not trying to deal with everything all in one go. And that’s how I would handle it. But we’re all different and we all do things in a different way. But for most of my patients I hope I will have told them and will have explained to them what the issues are, because if you understand the issues you realise it is not about dialysis, it’s about staying healthy for longer, and surely that’s what we all want.
 
The risk of progression to more advanced kidney impairment and to development of cardiovascular disease can be minimised by controlling blood pressure with tablets and by following healthy lifestyle advice such as eating a healthy diet, taking exercise, avoiding smoking and becoming overweight. Stage 4 or 5 kidney impairment is managed by a hospital specialist.
 

Professor Gene Feder explains that patients and their GPs both have a role in protecting kidney health; he talks about the support that general practices can offer patients in changing their lifestyle.

Professor Gene Feder explains that patients and their GPs both have a role in protecting kidney health; he talks about the support that general practices can offer patients in changing their lifestyle.

SHOW TEXT VERSION
PRINT TRANSCRIPT
So the specific patient objectives is, or are, to do with what we already know about weight, exercise, not smoking. All of those factors protect your kidneys as well; improve… in a sense the blood flow to the kidney by preventing blockages to those blood vessels, and they also then help prevent stroke and heart attack. So those are the key, you know, patient contributions. The GP contribution is really around appropriate medication, and the biggest risk of the kidney is from raised blood pressure.

So prescribing appropriately, prescribing the right medication – there a number of different families of anti… of blood pressure lowering drugs, and choosing the right ones needs to take into account what's happening to the kidney as well.

The other contribution that the GP can make is looking at the other parts of cardiovascular risk such as your cholesterol, your lipid profile as it's called, which needs to be treated if that’s abnormal, or needs to be treated if you’ve already had a heart attack or stroke and that actually also benefits the kidney. So it's a partnership between the things that the patients can do and the things that the GP can recommend.

And you mentioned that patients can do good things for their kidneys, for their kidney health by watching their diet, their weight and stopping smoking. What kinds of support could patients expect from their GP's surgery in helping them make those changes?

So it's supporting patients for behavioural change and I guess I'd put smoking at the top of the risk list. I mean, that’s part of the Duty of Care of the general practice. So many practices discharge that duty by having a practice nurse or a nurse practitioner who is particularly experienced at giving advice and support to patients. In relation to smoking cessation there now are very good nicotine replacement methods which, there is an additional benefit to talking about them and getting support and not just buying them across the counter. So a practice needs to be set up to give that support around smoking cessation; how to prescribe the nicotine replacement and needs to be in a position to give good advice on exercise; good advice on dietary choices. That should be part of modern general practice and, in my view, is just as important and there's some evidence for this, as prescribing the right medication.
 
 

Professor Gene Feder talks about the kind of conversation that GPs and patients with CKD should have about the pros and cons of taking blood pressure lowering drugs to reduce risks of future health problems.

Professor Gene Feder talks about the kind of conversation that GPs and patients with CKD should have about the pros and cons of taking blood pressure lowering drugs to reduce risks of future health problems.

SHOW TEXT VERSION
PRINT TRANSCRIPT
So the question about how we can encourage and support patients to take medication really comes down to having the ability to explain and to discuss the, if you like, the trade-offs and risks and benefits of taking medication because I think as doctors we sometimes assume that if we recommend it that it'll happen, and we know that’s not the case. So I think the right method is having an honest conversation about the benefit of the drugs, which may not be as much as the doctor assumes, and so making that explicit and having a conversation about what taking an additional medication might be in reducing the risk say of a heart attack or a stroke.

What the additional benefit might be in terms of preventing further decline of kidney function – that needs to be part of a conversation. The patient may decide that actually it's not worth taking that additional drug for an additional say, you know, five percent reduction in their ten year risk of a heart attack or stroke and that to me seems a very legitimate decision on the patient's part.

I think one of the challenges here is that, for the majority of patients who have reduced kidney function, the effect of that isn’t a substantially increased risk of kidney failure down the line later in life. In fact the majority of patients don’t have an increased risk of kidney failure. The effect of their reduced kidney function is an increased risk of heart attack and stroke. So it becomes part of that larger conversation that we have for any patient who, say has raised blood pressure and doesn’t even have any issues with their kidney, about “is it worth taking this drug because you're feeling perfectly healthy Mr Smith, for the next twenty/thirty years depending how old you are, in order to reduce your risk of a heart attack or stroke by X percent?”. And that is the crux of the conversation because people with reduced kidney function aren't ill, any more than someone with raised blood pressure is ill, any more than someone at an increased cardiovascular risk is ill. These are healthy people. It's just that they do have an increased risk of a problem down the line and that has to be the content of a conversation. GPs are used to having that conversation because it's not how we were historically trained but actually it's where we have to be now and , so my hope is that patients who do have blood tests and urine tests showing protein which suggest that they have reduced kidney function, are able to have that kind of conversation with their GP before making a decision about taking medication.
 
 

Dr Kathryn Griffith explains what people with early stage chronic kidney disease can do to help look after their kidneys.

Dr Kathryn Griffith explains what people with early stage chronic kidney disease can do to help look after their kidneys.

SHOW TEXT VERSION
PRINT TRANSCRIPT
I think the most important thing is that if your kidneys are working at a level which is not 100%, it is lower than 60%, then that you are aware of it, but you also understand it not to become anxious and not to become anxious about the need for dialysis in the future, but to be aware that there are perhaps things that you can do, like the healthy diet and the low salt, about keeping an eye on your blood pressure, making sure you do remember to take your tablets to lower your blood pressure, and because these things will help protect the kidneys. Please don’t smoke, because smoking damages that filter in the kidneys. It also has an effect on your blood pressure and your cardiovascular risk. So these things that you know about, you perhaps give more emphasis to if you know that your kidneys aren’t working so well.

Is there any dietary advice that would benefit patients with early stage CKD?

To, people think automatically because the kidneys get rid of end products, the proteins, that the things to avoid are proteins. My view for most of my patients is actually the big issue is to try and get them to lose weight, because if you can lose weight and get more active that will help lower your blood pressure, and that will help to protect your kidneys. The other big important factor is salt. So salt is in our diets. If you eat anything that has been made by somebody else it will have had salt put in it as a preservative, so bread, cereals, soups, anything that comes out of a jar or a tin will be full of salt. The highest salt product is actually Pot Noodle which has got the same salt content as sea water, so it can give you your salt intake and more for the day in a pot. So there is salt in every manufactured food, and the more salt we have the more that raises your blood pressure, and of course that is, will give you an adverse effect on your kidneys and your kidney function. It will cause you to, you could get puffy ankles and of course then what happens is people take water tablets and that has an, can have an effect on the kidneys. Best thing: avoid the salt in the first case. If you can do that, that will lower your blood pressure and that will help to keep you healthier. So I really focus on, on having a good, an optimum weight and to lower the salt in your diet. And that would be my focus, and just, just healthy eating. So fruit and veg, get out and about, be more active, because that is the best way to keep your kidneys healthy.

A lot of patients I have spoken to assume that there must be dietary advice out there that would help them, and they seem quite frustrated just by being told to eat healthily. They think information is being withheld for some unknown reason and that there must be something they can do beyond that.

Right. The big emphasis on kidney disease in the past has always been on those with more severe stages of kidney disease, so those who are coming to a stage when their kidneys need extra help and they might need dialysis. So all of the emphasis has been at that level and there have been some pretty horrible diets in the past for those people. They have different problems and they have much more severe problems about getting rid of these chemicals from the blood.

That isn’t the issue for our patients who have perhaps 50% kidney function. For them it’s not about the, helping their kidneys to work better by having less protein. For them it’s actually about helping their body to be more healthy and their cardio-vascular system be more healthy with the general advice we give for people who have got heart disease and high blood pressure, because at that level that’s the important thing for them. It’s their blood pressure and their cardiovascular system rather than thinking about the same dietary advice for people who have got much more severe stages of kidney disease.
 
NHS health policy on monitoring of early chronic kidney disease

Guidelines on early identification and management of chronic kidney disease were first published by the National Institute for Health and Care Excellence (NICE) in 2008 with the aim of reducing the proportion of cases of advanced kidney disease that were being referred late to specialist services, resulting in unnecessary suffering and deaths. The guidelines recommended that doctors should check for early changes in kidney performance in those most at risk to ensure more timely referrals, and by 2014, when the guidelines were updated and revised, the percentage of late referrals of advanced kidney disease had reduced from 30% to 19% [NICE July 2014].
 

Dr Kathryn Griffith talks about the NICE guidelines and other initiatives aimed at improving the management of people with chronic kidney disease (CKD).

Dr Kathryn Griffith talks about the NICE guidelines and other initiatives aimed at improving the management of people with chronic kidney disease (CKD).

SHOW TEXT VERSION
PRINT TRANSCRIPT
I would just like to tell you a little bit about the NICE Guidelines. Now you will be aware that NICE is a government organisation which reviews the evidence for the treatment of certain conditions. There is, has been a chronic kidney disease Guideline but we have just been involved in the past two years in updating it, and in July of 2014 the updated guidance will be published. There will also be advice to patients and there will be other activities for patient support around this. So it will give you some idea of what the evidence is for your treatment. It will also give you some idea of what you might expect or what you should expect in practices or at the hospital looking after your chronic kidney disease. So it’s very useful for you to look at and also to feed back on it.

I’d just also like to say a little bit about my role, because I am, part of my role as, other than being a general practitioner, is to be involved in work at the College of General Practitioners, because it was recognised that chronic kidney disease isn’t well understood in Primary Care, in general practice, and so the College has appointed myself as a Clinical Champion and I am also going to be having a Support Fellow, and the idea is to try and raise awareness for patients and for doctors about chronic kidney disease in Primary Care. We will also be developing educational materials, working with the patient groups, such as the British Kidney Patients Association and the NKF, about producing the right information for people in practice and, again, it is about making the patient the centre of their care and giving them the information that they need to help look after themselves better, and having that knowledge I think, I know knowledge is power but I think it is, it is power for people with chronic kidney disease and we need to try and get it right for you.

Your practice might be invited to be part of a National Audit, so again raising the quality of care. The HQIP, which is another national organisation, has funded an audit project throughout the UK. - Sorry - has funded an audit project which will take place in England and Wales and which your general practice may be involved in, and the idea is to help identify patients in the practices who have chronic kidney disease and to help look after them better. And the GPs will be given information about how that may best be done. And you may have a letter or see a poster up in the practice about this project, and you will be invited to feedback and ask about it. But all of these projects are working together to try and improve the care for yourselves and other people like you who have got chronic kidney disease.
 
 

Professor Gene Feder talks about GP attitudes to the original NICE guidance on CKD and that he believes the 2014 update has improved on the original.

Professor Gene Feder talks about GP attitudes to the original NICE guidance on CKD and that he believes the 2014 update has improved on the original.

SHOW TEXT VERSION
PRINT TRANSCRIPT
In the last ten years, as there’s, you know, been raised awareness of CKD and the pulling in of monitoring for CKD and its diagnosis in GP guidance, and indeed the Quality and Outcomes Framework, which is what has a very strong influence on what GPs do, there was a push back from GPs because of a perception that we were over-diagnosing patients and that we were taking, if you like, perfectly healthy patients who had some degree of um kidney function abnormality - and I’m putting it like that because a lot of this was based on blood tests alone - and one of the big improvements in the new guidance is it really highlights the importance of checking for protein in the urine and that being part of making a diagnosis of chronic kidney disease.

Whereas before – and this may have been ignorance just on the part of us GPs – there was an ambiguity about that and we were getting results back from the laboratory based on the blood test, like the creatinine or the glomerular filtration rate calculation, which put the patient in a- in a category, potentially in a category of CKD - when in fact there wasn’t any evidence that treating that or managing that would make any difference to that patient. So it seemed from a GP perspective a sort of spurious labelling of patients, which was often the reason why GPs did not mention it to their patients as well.

And unfortunately they then mixed into that patients who had reduced kidney function and leaking protein, so there was a sort of blurring of the boundaries. And I think that that caused the GPs to – not – let’s put it diplomatically - not to prioritise the issue of CKD. I do think with the new guidance there is a real focusing on those patients who do potentially have a problem, and where there is some evidence that managing it, particularly through blood pressure, is going to make a difference.

So this reaction on the part of GPs to over-diagnosis and if you like over-medicalisation of normal variation will I hope be a thing of the past. But it’s a challenge to general practice to try and respond appropriately to this problem. And I guess to temper the enthusiasm of specialists. And this is not just true for kidney specialists - all specialists are really enthusiastic about what they do. All specialists are worried about failure to diagnose, and that’s true if you’re an oncologist or a heart specialist or a stroke specialist or a kidney specialist. So general practice is a place where things are missed. And there is pressure on GP to not miss, and unfortunately that sometimes gets translated into a pressure to over-diagnose. And so GPs have this important role of trying to temper – to temper that enthusiasm. And I think the new NICE guidelines strike a good balance between the sort of- the generalist and the specialist perspective.
 

In the pages that follow, we will deal with many of these issues in greater detail, based on interviews with people whose kidney performance is being monitored due to mild or moderate impairment (CKD stages 2, 3a and 3b).

Last reviewed August 2017.
Last updated August 2017.
donate
Previous Page
Next Page