You probably don’t think about your kidneys until something goes drastically wrong with them. They work away silently, filtering waste from your blood, producing urine and helping to regulate hormones and blood pressure.
But these unsung heroes can come under strain in common conditions such as diabetes, cardiovascular disease and obesity, and from the mileage clocked up through ageing. In severe cases, the person may eventually need dialysis and to receive a kidney transplant.
Recent research suggests that about one in seven people over the age of 50 in Ireland have chronic kidney disease, yet many are unaware of it.
With the advent of new ways to manage and slow kidney damage, the race is now on to detect kidney problems in good time and spare people and the health system the burden of progressive kidney failure.
Ailing kidneys
“We generally classify a patient as having chronic kidney disease (CKD)) when a person’s kidney function is impaired for more than three months,” explains Austin Stack, professor of medicine at the University of Limerick and a consultant nephrologist at University Hospital Limerick.
He is pushing to establish a national surveillance system for kidney disease and recently led Health Research Board-funded research into chronic kidney disease in the Irish health system.
“We examined the results from blood tests on over 200,000 adult Irish patients from 2005-2011,” says Stack. “And we found that in a sample of adults over 18 in the health system, one in eight had signs of chronic kidney disease, even if they were not seeing the doctor for kidney issues. When we repeated the analysis more recently in 2014, we again confirmed that one in seven patients or almost 15 per cent of patients in the health system had chronic kidney disease.”
There are many reasons why a person’s kidney might start to lose function over time, he explains, including damage from high blood sugar in diabetes, inflammation in obesity and chronically high blood pressure.
There is also simply the wear and tear of working tirelessly for decades, notes Stack, who is principal investigator with the UL Kidney Health Consortium.
“People are living longer, which means all the organs will have to do a bit more work,” he says. “Along with that, we have a rising tide of hypertension, diabetes and obesity. And collectively that is going to create something of a tsunami of kidney disease in the future.”
A silent problem
Recent findings from the Irish Longitudinal Study on Ageing (Tilda) reflect the rising risk of kidney issues with age. The Trinity-based study of over-50s recently reported that CKD is rising among adults in Ireland, that almost one in seven participants in the study had chronic kidney disease and that the vast majority had no awareness of it.
“This was a stark finding,” says Prof Donal Sexton of Trinity’s School of Medicine, who is a consultant nephrologist and kidney transplant physician at St James’s Hospital.
“We looked at Tilda participants, a random population of people over age 50 living in the community and who are generally considered healthy, and we found that one in seven over 50 had chronic kidney disease, and that rose to around 35 per cent If they were over 70.”
One of the most startling discoveries, though, was that 98 per cent of the people in the study whose kidneys were impaired had no awareness of it.
“This is one of the issues with chronic kidney disease,” says Sexton. “A person may not have specific symptoms until the kidney damage is quite advanced. It’s a silent disease for the most part.”
As a clinician, Sexton seeks to slow the rate of damage for patients with kidney problems.
“We want to help them to delay or even avoid the need for dialysis and transplant,” he explains. “We also try and reduce their cardiovascular risk, because kidney disease in itself, whether people know they have it or don’t know they have it, is a very strong cardiovascular risk of stroke, heart failure, heart attacks and sudden death.”
The good news, according to Sexton, is that recent years have seen new treatments become available for patients. As well as the traditional approaches to managing blood pressure, such as Ace inhibitors [medicines that help relax the veins and arteries to lower blood pressure], doctors can now prescribe SGLT-2 inhibitors [lower blood sugar in adults with type 2 diabetes], which help to balance salt levels and reduce the strain on the kidney’s filtration units, and new diabetic and obesity medications, which can protect the kidneys even if the person does not have diabetes.
Stack agrees that the new treatment options are rapidly changing the landscape of kidney treatment for the better.
“In the last 10 years there have been some fabulous developments in science that reduce your risk of ending up in hospital looking at me,” he says. “We now have new treatments to protect kidney function, reduce the rates of progression, reduce the risk of cardiovascular events, protect patients’ lives and improve their quality of life and hopefully prevent or delay the need for dialysis.”
The new treatments strengthen the argument for setting up a more formalised screening programme in Ireland, according to Stack.
“When we are dealing with a chronic disease that is relatively asymptomatic, where you have a lot of people walking around undiagnosed, one of the big questions is whether it is common enough and harmful enough that we should develop a national screening programme for it, especially to target the high-risk groups. That has been a debate for a number of years internationally around chronic kidney disease,” he says.
“And now the research convincingly shows yes it is common and harmful and on the rise, while at the same time, we now have new ways to treat people if we can detect the kidney problems in good time.”
In practice, Stack would see the screening taking place in primary care, such as the GP clinic, with simple blood and urine tests to look at kidney function.
“We don’t have to get out a magnifying glass to locate people who might be at risk,” he says. “We need to be keeping an eye on people with high blood pressure, people with diabetes, people with a family history of kidney disease, and screening them when they go to the GP, then getting them on to the best plan to manage the condition if their kidneys are not functioning as well as they should.”
New biomarkers, future treatments
Some of the standard tests for kidney function have the advantage of being relatively easy to carry out, such as measuring levels of creatinine in a blood sample or detecting protein leaking into a urine sample. But we also need a more nuanced approach to measuring how kidney damage worsens, according to Prof Catherine Godson, a full professor of Molecular Medicine at University College Dublin.
“The problem we see now is with the biomarkers of progression,” she says. “We need dynamic markers that can tell when a person has early-stage disease and then can reliably tell you how the damage is developing. That is going to be really important for monitoring clinical trials of new treatments, where you can tell what is going on with the kidney and see if there are even modest changes happening.”
She is also intrigued by the success of the new drugs in protecting the kidney.
“The GLP-1 analogues [increases the levels of hormones called incretins] and SGLT-2 inhibitors that are revolutionising kidney treatment were not initially developed for that purpose, they were developed to tackle diabetes but they seem to have a positive effect on the kidney even independently of controlling blood sugar,” says Godson, who directs the UCD Diabetes Complications Research Centre. “They challenge the conventional wisdom and we need to research and better understand how they work, as they could point to more new treatment approaches too.”
Godson is working with nephrologist Dr Dean Moore on a class of naturally occurring molecules called lipoxins, which encourage the body to resolve or quench damaging inflammation.
Moore, a specialist registrar in nephrology at the Mater hospital, has been testing lipoxins on samples of blood from patients with chronic kidney disease.
“We know from studies in lab models that these lipoxins can protect kidneys,” he says. “Then when we add them to patient blood samples we can see they have the ability to affect the immune system positively. It’s a provisional finding at this stage, but it is encouraging.”
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