Kidneys and Kidney Disease

By making urine, the kidneys get rid of extra water, salt, and other chemicals that the body does not need. The kidneys also keep water and other substances the body needs from being lost in the urine. The kidney's other functions are:

Body Fluids

The kidneys regulate the removal or retention of body fluids. If a person takes in a large amount of salt (sodium) in their diet, they become thirsty and may drink more fluid. If the kidneys are normal, they remove the extra salt and fluid in the urine. If the kidneys are not working properly, the extra salt and fluid build up in the body and can cause the hands, feet and the face to swell. This swelling is called edema. If there is too much fluid in the body, it can collect in the lungs and make breathing difficult. It can also put extra strain on the heart.

Body Chemicals

The normal kidney balances the internal chemistry of the body. The kidneys not only remove certain chemicals, but also keep other substances and chemicals the body needs. Potassium is one of the substances the body needs for normal heart and muscle function. When one eats food with potassium in it, the kidneys work to keep a normal level of potassium in the blood. If the kidneys are not working properly and the potassium builds up in the blood, then muscle function is affected, which may cause weakness. Too much potassium in the blood can also affect the heart, at times to a dangerous degree.

Several chemical reactions in the body produce acid substances. Normally, the body maintains a healthy balance of acid. If too much acid substances build up in the body, the kidneys respond by adding a buffer to normalize the balance. If the kidney is not working, the normal acid balance cannot be controlled, which can cause a condition called acidosis. Normal kidneys also balance other substances in the body that include protein. Also, certain renal diseases result in a leak of protein into the urine, which can even contribute to malnutrition.

Waste Products

Waste products are formed from the breakdown of the protein contained in foods and from normal muscle activity. When the kidneys are not functioning, these waste products build up in the blood and may act like a poison to the body.

The buildup of waste products can cause one to be tired, weak, and nauseated. This is sometimes called uremia, uremic syndrome or uremic poisoning, because urea is one of the waste products that builds up.

Hormones

Hormones are substances released by glands and organs to stimulate a specific activity elsewhere in the body. Normal kidneys release several hormones, three of which are renin, erythropoietin and an activated form of Vitamin D. Renin helps to regulate blood pressure. In non-functioning kidneys, the release of rennin can become uncontrollable and can cause high blood pressure. The kidneys release erythropoietin to help the bone marrow make red blood cells.

When the kidneys are not working, fewer red blood cells are made, which is a cause of anemia. Activated Vitamin D regulates calcium absorption from food and helps maintain normal bone structure. When renal function is impaired, less calcium enters the body and bone disease can result.

What is Renal (Kidney) Disease?

People are born with two kidneys. Each is about the size of a fist, and they're on both sides of your spine at the bottom of your rib cage. Together they weigh about 10 to 12 ounces. When your body uses the food you eat and the liquids you drink, there are waste products that your kidneys filter out as urine. When your kidneys are healthy, they keep your whole system in balance. They stimulate your body to make red blood cells. They release hormones that help to regulate growth and blood pressure, and they help to keep your bones healthy.

Usually, you don't have to worry about any of this. But when your kidneys become damaged or diseased, then it's a different story. Waste products and fluids build up, and you may feel weak or tired. You may feel sick to your stomach. You may lose your appetite or feel irritable and have trouble thinking clearly. Or it is possible that your kidneys may stop working so slowly that you won't notice any of these symptoms. That is why it is important to visit your doctor regularly and be aware of the symptoms of renal disease.

If any of these symptoms occur singly or in any combination, consult your physician immediately:

  • Swelling of parts of the body, particularly eyes, ankles or wrists.
  • Burning or abnormal discharge during urination.
  • Changes in the frequency of urination, especially at night.
  • Lower back pain.
  • Bloody, foamy or coffee-colored urine.
  • High blood pressure.

Your doctor can determine if your kidneys are diseased or damaged in two basic ways. He or she can assess the function of your kidneys by estimation of the glomerular (or kidney) filtration rate and screening of the urine for protein or albumin. These tests can be done with a simple blood draw and urine sample.

Are You at Risk for Renal Disease?

  • Do you have high blood pressure?
  • Are you diabetic?
  • Do you have a family history of renal disease?

If you answer "yes" to any of these, ask your doctor to send a spot urine sample test for urinary albumin and creatinine, test your urine for protein and test your blood for creatinine.

Urinary albumin excretion is expressed per mg. creatinine in urine.

30 mcg/mg - 300 mcg/mg = microalbuminuria
>300 mcg/mg = macroalbuminuria (significant proteinuria)

There are five stages of Chronic Kidney Disease (CKD) based on glomerular filtration rate or GFR: GFR is calculated from your blood creatinine, age, race and gender. Calculate your GFR. Once you have your GFR value by using the calculator, you can determine the approximate level of renal disease. You should double-check your GFR with your physician.


Stage 1 GFR equal to or more than 90 may be slight renal damage with normal or increased GFR
Stage 2 GFR 60-89 mild decrease in renal function
Stage 3 GFR 30-59 moderate decrease in renal function
Stage 4 GFR 15-29 severe decrease in renal function
Stage 5 GFR less than 15, renal failure dialysis or transplant is the necessary form of treatment

Medical Terms

Creatinine: A substance found in the blood, urine and muscle tissue. It is measured in blood and urine tests to determine the level of kidney function. The normal range for creatinine in the blood is 0.7 - 1.2 mg/dL

Glomerular Filtration Rate (GFR): A test that determines renal function by measuring creatinine clearance.

Microalbuminuria: A small amount of protein found in the urine that may signal the early stages of renal disease in people with diabetes.

Proteinuria: A condition in which the urine contains large amounts of protein, a sign that the kidneys are not functioning properly.

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This page was last updated: June 20, 2013

         
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