So AKI is acute kidney injury and this is a really important condition. It’s important for healthcare to recognise it happens in the community and also in hospitals too. And in both settings it’s really important that we rapidly recognise that it’s going on and take steps to treat it. What is it? Well, it’s a sudden reduction in the body’s ability to filter the blood and produce urine. And typically this would be detected by a blood test, where we would see a rise in the patient’s creatinine. And that’s, creatinine is a waste product that the kidney gets rid of for us, and so when it rises in the blood it shows the kidney isn’t getting rid of it as well as it should be. And that’s our sign to think about AKI as being a cause of this and what we might do about it.

In our frailer and older patients they may have a sudden change in their function, reduced mobility or just not being quite right, and in that setting, often that’s a cause of AKI as well. In very mild stages patients may not notice anything but we would know that typical causes might be dehydration. Some medications can do it as well, if there have been changes in medications recently. Infections as well. And also AKI can happen at the same time as other significant conditions where maybe the kidney hasn’t been the primary focus of a condition or disease, if you like, but it’s being affected because another serious disease is happening, like overwhelming or generalised infection, or chest infection, for example.

So what’s the difference between CKD and AKI?

So the difference between AKI and CKD, if you like, is that chronic kidney disease represents a stable state over a longer period of time, where day in day out the kidneys are functioning but functioning less well than we would like, and that’s pretty stable day in day out. AKI is when theres a sudden reduction in kidney function; and, usually, that’s associated with symptoms or with a change in function. In early stages of AKI it can be, the patient may not notice anything until it gets to a more advanced stage. But, by and large AKI is associated with acute illness, often perhaps due to dehydration or to a change in medication, or the kidney is being affected by another disease process such as pneumonia, potentially heart failure as well.

Why does early stage CKD make you more prone to AKI? Well, a lot of patients with early stage CKD are older. Many of them may have conditions such as hypertension and diabetes, and a number of medications will be, could be prescribed for those which affect the kidney, for example, ACE inhibitors or angiotensin receptor blockers. These drugs are a really important part of our ability to reduce risk long term in patients with hypertension and some with diabetes too. So they’re important drugs that are beneficial for patients if they’re handled in the right way. Whereas after, say, a period of diarrhoea or vomiting or dehydration, sometimes those drugs can start harming the kidney, and the earlier we can recognise that’s happening and stop those medications while the patient’s kidney function recovers, the better; and then they can go back on those medications safely at a later date.

So some of the risk around AKI for patients who have early stage CKD is around some of the medications they’re taking. It may be an indicator of also age and frailty as well. We know that our older and frail patients are more susceptible to dehydration in hot weather and are at greater risk of their kidney being involved in a condition like pneumonia or heart failure, for example.

So that explains some of it. There are also probably some other mechanism around how the kidney functions that is affected in CKD that we haven’t fully worked out the mechanism yet, how it goes from A to B. But understanding that CKD is a prominent risk factor for AKI is important for all doctors and for all patients who are affected as well, so that communication can be delivered ahead of time, and how to, how patients respond on days when they’re unwell and they’re losing fluid and salt through diarrhoea or vomiting, or because it’s just been very hot and they haven’t been able to keep up with their fluids.

Some of this may be to do with the blood tests. So these are blood tests that GPs have been doing for years and years and years on their patients and they haven’t been told that the numbers they’re getting back from the lab are abnormal. And the same patient given the same blood test now comes back with a note from the lab saying, actually, this is abnormal, when for years it hasn’t, for years it’s been in what’s called the normal range. And I think what’s happened is research has very much changed that perspective. For those individual doctors, they haven’t seen those patients getting more unwell with a different label, it’s just come from the laboratory. And that might explain why some doctors are reluctant because they don’t see there being any particular change in this group of patients but the laboratory advice is coming back different. However, it’s clear, from recent research, that there is an excellent reason to change how the laboratory reports these blood test values because they actually do show theres a higher risk. And, for some doctors who’ve maybe been practising for years and seeing these results as being normal, it’s quite a paradigm shift for them to then suddenly say this is a disease.

When I approach this as a researcher as well, as well as a clinician, it’s pretty clear to me from what we call epidemiology – which is looking at what happens to populations of patients who have the same kind of condition in terms of, say, the risk of developing heart failure or having a cardiovascular event, such as a heart attack or a stroke – it’s pretty clear that, when someone does have chronic kidney disease, those risks are raised and it’s important, therefore, that we in the medical profession are able to communicate and talk about that risk and advise patients on the various options that are available to reduce risk, so people can decide what it is that suits them best as how they can keep themselves as healthy and living as long a life as possible.

So we are often caught from the research and the practice side from sort of two ways of looking at it, if you like. So somebody with chronic kidney disease at an early stage, for example, say, stage 3A, they will, you know, walk into a GP’s surgery, they may have hypertension, may have diabetes or may have none of those two but perhaps would be slightly older, and they’ll look quite healthy. And I think in order for some doctors to call that a disease state they find quite challenging.

When I look at it from the perspective of risk and what it is that I need to be telling my patients about things, conditions that they may have that raise risks and what to do about it, then I think it’s important that those labels are used because they have meaning.

So, although I’m aware that there are doctors that do not use this label, I look at it from a slightly different angle and say, well, don’t just look at the patient in terms of how they appear today, you need to think about risk long term. And also it’s important that diseases are diagnosed in a pretty systematic way, so the same for each patient each time they will see a doctor or a different doctor. And it may be that we need more research evidence might convince some doctors who don’t want to call this a disease.

And I think what we don’t want is for this to kind of dissolve into what one might call a semantic argument, an argument about meaning. Is it about the risk of a disease or a disease in itself? And you can say that’s a bit similar to like high blood pressure – hypertension – because that causes, you know, there is a risk of things like heart attack, stroke, heart failure, and declining kidney function, happen because of high blood pressure. And doctors are very happy to diagnose that and manage it where appropriate. And you can see sort of chronic kidney disease in sort of the same way. It doesn’t necessarily make you unwell in the early stages, so the patient with hypertension or with early stage chronic kidney disease will look quite fit and healthy, potentially, but in the hypertension case – patients with high blood pressure – doctors will very happily make a diagnosis and offer treatment and lifestyle advice and talk about how, what kind of treatment regimen would be easier for a patient to adhere to or what kind of treatment goals the patient may want to achieve. And we could say the same for chronic kidney disease. It’s not necessarily a disease state like a heart attack or a stroke, but it raises risks and, therefore, giving it a label that makes people recognise it, apply it systematically and then act in terms of advice and informing patients what their risks are, is really important.

So, whilst I know there are some doctors that don’t like using the term, for me it’s pretty clear and unambiguous that we should be using this term. We should be applying it systematically so patients get the same view and the same understanding of their illness at every healthcare contact, where they may want to raise it and talk about it as an important issue for them. And also it’s important I think that we fully inform patients of their risk so that they’re able to take whatever action from a range of possibilities that there are from the clinical perspective.

So chronic kidney disease is an extremely important risk factor for cardiovascular disease, such as heart attack or stroke. And we know that patients, some patients with chronic kidney disease also have other problems, such as high blood pressure and diabetes, both of which will also increase the risks of cardiovascular disease. However, in the studies that have looked at large populations of patients with chronic kidney disease, and with high blood pressure, and with diabetes, among other things such as high cholesterol, which can also increase vascular disease, it’s clear that it’s not just the fact that patients with chronic kidney disease have other things that are making them at increased risk, theres something about chronic kidney disease itself that raises risk. It’s not just due to the other comorbidities or conditions that a patient may have. And we don’t yet know fully why that’s the case. There are a number of very good studies that pinpoint certain hormones of the kidneys involved with regulating, particularly to do with blood pressure and salt and water. But we don’t yet fully know why chronic kidney disease increases risk.

As kidney function declines, blood pressure becomes more difficult to control. Blood pressure variability may play a part in that. We know that patients with very advanced chronic kidney disease have very variable blood pressures. We also know from other evidence that patients without chronic kidney disease who have variable blood pressure are at more risk of stroke and heart attack than, say, patients whose blood pressure doesn’t vary quite so much. That’s all quite early research findings. We haven’t, we don’t yet know how we can use that in clinical practice but we are, and a number of people are undertaking studies that will look into that. So I think the short answer is, although we know that chronic kidney disease does raise risk and does it in its, on its own merits, if you like, we don’t yet fully know what that mechanism is, and when we do, well be able to think about alternative therapies that might be, might help us to target specifically the cardiovascular disease risk of chronic kidney disease.