Is your kidney function limited and do you find yourself wondering what precautionary measures you can or even should take? In this article, you will learn how often you should visit your doctor for a check-up, which values are examined and how you can keep track of everything.
Why is it important to check my kidney function regularly?
Not all kidney diseases are the same. One of the main tasks of your kidney is to clean the blood. How much blood your kidney cleans per minute can be shown by calculating the glomerular filtration rate (=GFR) or the estimated glomerular filtration rate (=eGFR). To calculate the GFR, among other things, the amount of urine you excrete in 24 hours (=24-hour collection urine) is needed. This is quite cumbersome. To calculate eGFR, you do not need this value, which is why eGFR is more commonly used to monitor kidney function. With the GFR, renal insufficiency can be roughly divided into 5 stages, with the function of your kidney decreasing more and more from stage 1 to stage 5:
If there is no other indication of a problem with your kidney - such as an increased amount of protein in the urine (=proteinuria) - stages 1 and 2 are not considered a disease. These two stages simply call attention to the fact that your kidneys aren't working as well as they used to.
However, just because your kidney failure was once assigned to a particular stage doesn't mean it will stay that way. Your doctor may have talked about the progression of your kidney failure. Rapid progression means that your kidney function is declining rapidly. A slow progression means that your kidney values, and therefore your kidney function, stay relatively the same over the long term. In order to keep an overview of the progression and to be able to intervene as early as possible in the case of progressive deterioration, it is important that you have the function of your kidneys checked at regular intervals by your family doctor or your nephrologist. The recommended time interval for the check-ups depends mainly on the current stage of your renal insufficiency.
How often should I have my kidney function checked?
In addition to the GFR/eGFR, the amount of protein you excrete in your urine plays an important role in determining the stage of your renal insufficiency. In order for your doctor to determine the time interval between your check-ups, both values are taken into account. In simple terms, the German Society for General Medicine and Family Medicine (DEGAM) recommends the following:
- Up to a GFR of 45 ml/min you should go for a check-up at least once a year.
- If your GFR is less than 45 ml/min, it is recommended to have a check-up at least twice a year.
- If your GFR is less than 15 ml/min, a check-up is recommended at least four times a year. Depending on the extent, dialysis therapy may already be necessary at this stage. In this case, different guidelines apply again.
But what exactly is normally examined by your nephrologist during these follow-up examinations?
eGFR and serum creatinine
The eGFR should always be determined as part of the specified follow-up checks. As mentioned above, this is the estimated glomerular filtration rate, which indicates how much blood your kidneys clean per minute. To calculate this value, you need several pieces of information. One of them is the amount of creatinine in your blood (=serum creatinine). Creatinine is a so-called "waste product" that is produced in the body primarily during the energy production of your muscles and is excreted via the kidneys. If the kidneys can no longer clean your blood as usual, more creatinine remains and the serum creatinine level increases.
The serum creatinine value and the eGFR value thus provide information about your kidney function and are compared with your previous values for monitoring purposes. In this way, you and your treating physician receive information about the development of your renal insufficiency. In this way, the progression of your renal insufficiency described above can also be closely monitored.
Blood pressure
High blood pressure (=hypertension) can be both a cause and a consequence of chronic renal failure. Permanently high blood pressure is not healthy for your kidneys and can also put a strain on your cardiovascular system. Therefore, your blood pressure should not only be measured as part of your check-ups, but should also be checked regularly by you at home. In general, your blood pressure should not exceed 140/90 mmHg. However, if high blood pressure values occur regularly, do not wait until the scheduled check-up, but contact your doctor earlier.
Protein in urine
When the kidney cleans your blood and excretes the "waste" in the urine, it normally contains only a small amount of protein. However, kidney disease can cause increased excretion of protein in the urine (=proteinuria). The amount of protein in the urine should have already been determined once as part of your initial diagnosis. If increased amounts of protein were detected in the urine (more than 30 mg/g), then a check should be carried out at regular intervals as part of your progress monitoring. For this purpose, the so-called albumin-creatinine ratio (=ACR) is usually determined.
Diabetes mellitus
The main cause of chronic renal insufficiency is diabetes mellitus. However, high blood glucose levels not only damage the kidneys, but - like high blood pressure - also put a strain on your cardiovascular system. Therefore, the optimal adjustment of the blood sugar is in the foreground.
If you have diabetes, your fasting blood glucose level (= blood glucose measured 8 hours after your last meal), your HbA1c (=long-term blood glucose level), your kidney function and the amount of protein in your urine are regularly tested. The ACR value mentioned above is often used for this purpose. For more detailed information on this, it is best to talk to your doctor.
Anemia
The kidney performs various tasks in your body. Among other things, it stimulates the formation of new red blood cells (=erythrocytes). Your red blood cells consist to a large extent of the red blood pigment - hemoglobin. Oxygen binds to this red blood pigment and is transported from one cell to the next by your red blood cells.
If your kidney function is impaired, your body may make fewer red blood cells. This means that less hemoglobin is available to transport oxygen. Too little hemoglobin in your blood is also called anemia. If you have anemia, you may often feel tired, have difficulty breathing, especially during exertion, and be pale.
If the hemoglobin value (=Hb) is below 12 mg/dL in women with chronic kidney disease and below 13 mg/dL in men, this is called anemia.
Since the risk of developing anemia is higher in people with chronic renal failure than in healthy kidney patients, the Hb level should be determined regularly:
- If your GFR is less than 45 ml/min, you should have your hemoglobin level determined by a blood draw at least once a year.
- If your GFR is less than 30 ml/min, it should be determined twice a year.
In addition to impaired kidney function, iron deficiency can also cause anemia. If you have been diagnosed with anemia, the laboratory parameters ferritin and transferrin saturation should also be determined to confirm or refute iron deficiency as a possible cause. If you have any questions or uncertainties, your medical team will be happy to help you at any time.
Other laboratory values
Other important laboratory values in chronic renal failure are: Vitamin D, calcium, phosphate and parathyroid hormone.
Vitamin D has a major impact on our bone stability and is both ingested through food and produced by the body itself. However, no matter how the body gets its vitamin D, in order for it to perform its functions in the body, it must be activated by the kidney. Therefore, renal insufficiency can lead to a lack of active vitamin D and, as a result, there is less stability in the bones.
The stability of the bones is created, among other things, by the incorporation of calcium and phosphate, which is taken in through the diet. In addition to vitamin D, the so-called parathyroid hormone, which is formed in the parathyroid gland, ensures sufficient calcium in the blood. Vitamin D has a positive effect on bone stability by promoting the incorporation of calcium into the bones. Parathyroid hormone, on the other hand, ensures that calcium is released from the bones. Too much parathyroid hormone can therefore weaken the bones.
Although chronic renal insufficiency can affect bone metabolism in its early stages, it often does not lead to symptoms until the later stages. If your GFR is below 30 ml/min, these values should therefore be determined in any case. Before that, it is not routinely recommended. How often you should be checked thereafter is very individual and best discussed directly with your nephrologist.
Medications and renal insufficiency
Many medications are excreted by the kidneys and can impair their function. Therefore, the medications that you take permanently should be checked once a year by your doctor and, if necessary, changed to more kidney-friendly preparations. In addition, the excretion of medications may be slower. This may make it necessary to adjust the dose.
Support from the Mizu app
We've discussed so many different values now, it's easy to get confused. The Mizu app can help you keep track of them all. For example, you can document your kidney values, such as the eGFR or your creatinine, and values such as your blood pressure in your diary within the app at any time. The app even shows you the history of your values in an overview. You can also create a medication plan so that you always have your long-term medication at hand.
