- Kidney Function Test

The medication that we use to treat your heart failure can affect your kidney function, which is why we insist on regular blood tests. When we take blood what we are looking for is to see how your kidneys are coping with the medication and to ensure that they are cleaning your blood adequately.

The kidneys are a pair of vital organs that perform many functions to keep the blood clean and chemically balanced. They are bean-shaped organs, each about the size of a fist. They are located near the middle of the back, just below the rib cage, one on each side of the spine. The kidneys are sophisticated machines where they process the blood to sift out waste products and extra water.

Waste in the blood comes from the normal breakdown of active tissues, such as muscles, and from food. The body uses food for energy and self-repairs. After the body has taken what it needs from food, waste is then sent to the blood. If the kidneys did not remove them, these wastes would build up in the blood and damage the body.

The kidneys measure out chemicals like sodium and potassium and release them back to the blood to return to the body. In this way, the kidneys regulate the body's level of these substances. The right balance is necessary for life.

People with healthy kidneys have 100 percent of their kidney function. Small or mild declines in kidney function (as much as 30 to 40 percent) would rarely be noticeable. Kidney function is now calculated to find the estimated glomerular filtration rate (eGFR). Your eGFR corresponds to the percent of kidney function available.

If the kidneys become damaged, they carry on producing urine but become less efficient at removing waste products from the blood. Instead, the waste products continue to circulate and build up in the bloodstream.

At the same time, without the hormones that a healthy kidney would produce, the bone marrow becomes less efficient at producing red cells, so anaemia develops.

For some patients, this may be a very gradual process. Over time, however, it can cause quite a wide range of symptoms but not everyone will experience all the symptoms. Also, because it can be such a gradual process, some people don't even realise the effect the symptoms are having until - with treatment - they begin to feel better.

This is why it is important that we monitor you kidney function regularly so that when a discrepancy is noticed, we are able to act quickly to adjust your medication and stop your kidneys from further harm.

If you have any further questions about your blood tests, please speak to your nurse or doctor.

Taken from the Heart Failure Newsletter No13