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  • Dr. Mike Purdon

Kidney disease: The ABC's of the GFR and CKD

You are probably reading this because we have raised some concerns about your kidneys. We hope that this article helps you understand the function of the kidneys, the terms and the tests that we use and some of the ways that we can help you protect your kidneys. Let's answer some common questions.

What do the kidneys do?

I like this description from Healthlink BC: “Your kidneys have the important job of filtering your blood. They remove waste products and extra fluid and flush them from your body as urine. When your kidneys don't work right, wastes build up in your blood and makes you sick.” You might be surprised to learn that the kidneys are also involved in the control of your blood chemistry, your blood pressure, the production of blood cells, the health of your bones, and the in the control of the acidity of your blood. Perhaps because of all of the critical functions they play, most of us are born with two kidneys and have more kidney function than we need. This is why healthy people can donate one of their kidneys and still live a perfectly normal life. In fact we can lose a great deal of our kidney function without any symptoms and by the time our tests are abnormal, we have lost a substantial amount of our function. If we have detected a problem, it has likely been present for quite a long time and it is important for you to understand what we can do about it and the tests we use and the terms that apply to this condition.

How do we test how well the kidneys are working?

We can look at the kidneys with blood tests, urine tests and by taking pictures with ultrasound or CT scans. There are a lot of tests that measure the health of your kidneys, but let’s focus on one of the most common tests of kidney function-a blood test called the GFR or glomerular filtration rate. The GFR is a calculation made by the lab that tells us how fast your kidneys are processing your blood. The GFR changes over time, but if it is consistently below 60, we worry about the health of your kidneys. Most of the time we will be using this measure to tell how well your kidneys are working and whether or not you have chronic kidney disease (CKD)-more on this later.

What are the symptoms of kidney disease?

The National Kidney Foundation in the United States says it well: “Kidney disease does not happen overnight. It happens slowly, and in stages. Most people in the early stages do not have any symptoms. They may not know that anything is wrong. But if it is found and treated, kidney disease can often be slowed or stopped.” In fact, we hope that you are reading this long before you have any symptoms at all, and that we can work together to try to make sure that you never do.

If kidney disease gets worse, wastes can build to high levels in your blood and make you feel sick. You may get other problems like high blood pressure, a low red blood cell count or anemia, weak bones, loss of appetite and nerve damage. Damaged kidneys can lead to symptoms such as intense itching, swelling, fatigue, dry skin, or insomnia. Of course, all of these symptoms can also have other causes.

What is chronic kidney disease?

Sometimes a kidney blood test can become quite abnormal but return to normal quickly. For example severe dehydration can cause strain on the kidneys, with changes in the GFR that quickly return to normal with hydration and we would not use the term chronic kidney disease (CKD). If you are reading this, we have likely detected abnormalities in your GFR blood test over a six month period at least and it means that the kidneys are damaged.

This term can be distressing to hear because the words “chronic” and “disease” seem bad, but it is quite likely that, if you are reading this, that you are feeling perfectly well, and that we have simply detected a change in your GFR and that this change has persisted for at least six months. Like most diseases, there are stages and more information about this can be found here.

How did I end up with chronic kidney disease?

CKD is not a disease that you can catch or spread. There are some common causes that we are going to want to rule out as CKD can be caused by a number of things, although sometimes, we won't be able to tell you why your kidneys have been damaged.

Chronically elevated blood pressure is probably the most common cause of chronic kidney disease and we will spend a lot of time monitoring and talking about how we can get your blood pressure just right to protect the kidneys. Diabetes can also hurt the kidneys over time and chronically high blood sugar can slow kidney function. Sometimes over the counter or prescription medications can hurt the kidneys. Blockages or restriction in the flow of urine, such as when a man’s prostate enlarges, can also hurt the kidneys. Some genetic conditions, autoimmune disorders and infections are associated with reduction in kidney function. In other words, when we first identify CKD, we will often suggest testing that helps us search for the cause so that we can help you stop further injury to your kidneys. Of course, it is very important that we also know all of the prescription and non-prescription medications that you are taking so that we can tell you which ones are safe for the kidneys and which ones to avoid.

What are the consequences of chronic kidney disease?

If chronic kidney disease worsens symptoms can start to develop. You may feel sick, tired, itchy or irritable. Sleeping can be difficult and swelling or edema can occur. Blood pressure can rise and blood counts can go down. Bones can weaken. If the kidneys fail altogether, you cannot live without dialysis or a transplant.

Even in early phase kidney disease, the risk of heart and blood vessel diseases is increased and we may recommend treatment with medication to reduce these risks.

How is chronic kidney disease treated?

Healthlink BC puts it well: "The goal of treatment for chronic kidney disease is to prevent or slow further damage to your kidneys. Another condition such as diabetes or high blood pressure usually causes kidney disease, so it is important to identify and manage the condition that is causing your kidney disease. It is also important to prevent diseases and avoid situations that can cause kidney damage or make it worse."

While medications may be an important part of the treatment of chronic kidney disease, exercise and diet are also critical in keeping your kidneys healthy. Healthlink BC offers a nice overview of dietary changes here. You may also want to call or email the 811 dietician to review a healthy diet for patients with chronic kidney disease. This service is free for all British Columbians. Please also talk to us about an exercise program that is safe for you.

Some key points from the National Kidney Foundation (lightly edited):

•Healthy kidneys do many important jobs. They remove waste products and extra water from your body, help your body make red blood cells, help control blood pressure, and keep your bones healthy.

•When you have kidney disease, your kidneys slowly lose the ability to do the important jobs that keep you healthy. The leading causes of kidney disease are diabetes and high blood pressure.

•If you have risk factors for kidney disease, get tested for it.

•Your GFR number helps your healthcare provider know how much kidney function you have.

•If you have kidney disease, you will need to follow a treatment plan that may include taking medicines, restricting salt, limiting certain foods, getting exercise, and more. Your treatment plan will depend on your stage of kidney disease and any other health problems you may have.

•Finding and treating kidney disease early can help slow or even stop kidney disease from getting worse.

•If you have kidney disease, learn all you can about it. You are an important member of your healthcare team. How carefully you follow your treatment plan may affect how well you do.

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