Kidney School™—a program of Medical Education Institute, Inc.

Module 1—Kidneys: How They Work, How They Fail, What You Can Do

water jug

How Kidneys Work

What might happen if your water treatment plant stopped removing toxins and waste from your drinking water? Surely you and everyone else who drinks city water would be sick in a short time.

We may give it little thought, but our health depends on the water treatment plant doing its job. A very similar process must occur in our bodies to filter out toxins and waste from our blood.

Of course, we have our own built-in treatment plant: kidneys. Far more complex than any water treatment plant, kidneys keep constant levels of water and key chemicals in our bodies.

Here's how it works. As you eat and drink, your body takes what it needs for energy, nutrients, and self-repair. Leftovers and extra water your cells don't need become wastes. Some of the wastes end up in the bloodstream and must be filtered out to keep you healthy. The key job of the kidneys is to maintain homeostasis—a balance of water and chemicals. They do this by filtering your blood.

As you know, with every heartbeat, blood is pushed through your body. This means healthy kidneys work to clean the blood 24 hours a day, 7 days a week. Each day, kidneys filter out about 2 quarts of extra fluid and wastes (urine). Drop by drop, urine collects in the bladder, until... Presto! Wastes are removed when you urinate.

Kidneys Send Messages

Kidneys "talk" to the rest of your body by making an enzyme and two hormones. Enzymes are proteins that help certain body functions. Hormones are chemical messengers made in one part of the body that act on another part.

Renin is an enzyme. It helps control how much sodium (salt) and fluid the body saves and how relaxed the blood vessels are. Most people with kidney disease need blood pressure pills because their kidneys no longer control blood pressure.

Erythropoietin (EPO) is a kidney hormone that tells the bone marrow to make new red blood cells. Many people with kidney disease have anemia, a shortage of red blood cells, that makes them feel very tired. Injections of EPO are used to treat anemia, along with iron.

Kidneys also make calcitriol, a hormone that helps the body absorb calcium from food. Without calcitriol, the body steals calcium from the bones. Over a long period of time, this can cause bone disease. Calcitriol injections or pills are used to help avoid bone disease in people with kidney disease.

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