Kidneys perform crucial functions, which affect all parts of the body. Normally, there are two kidneys, one on either side of the spine under the lower ribs. The kidney serves several main functions:
- Elimination of Waste Materials
- Regulation of Fluid and Electrolyte balance
- Regulation of Blood Pressure
- Production of renin(activates a hormone called angiotensin) and calcitrol, the active metabolite of vitamin D
- Production of the hormone, erythropoietin
Your kidneys receive and clean your blood everyday. The wastes in your blood come from the normal breakdown of active muscle and from the food you eat. Your body uses the food for energy and self-repair. After your body has taken what it needs from the food, waste is sent to the blood. Blood then enters the kidneys through an artery. Each kidney contains thousands of nephrons. The nephrons separate waste matter from plasma, the liquid part of your blood. The wastes, with a small amount of water in which they are dissolved are excreted as urine. Wastes such as creatinine and urea, must be excreted properly. Their levels in the blood must be kept at the correct levels for the body to maintain excellent health.
The kidneys regulate vital electrolyte balances that must be kept within extremely narrow limits compatible with life. Electrolytes are dissolved salts, the most familiar being sodium, an element of common salt. Potassium is another common electrolyte which the kidney regulates.
The kidneys control blood pressure in several ways. If blood pressure rises, the kidneys increase their excretion of salt and water, which lowers blood volume and brings the blood pressure back down to normal. If blood pressure falls, the kidneys decrease their excretion of salt and water, so that blood volume increases and blood pressure returns to normal.
The kidneys can also regulate blood pressure by secreting renin. Because the kidneys are important in controlling blood pressure, many kidney diseases and abnormalities can cause high blood pressure.
The kidneys produce calcitrol, an active metabolite of vitamin D, which is important in the formation of bone. During kidney failure, bone formation may be impaired.
The kidneys also secrete a hormone called erythropoietin. Hormones are substances released into the blood stream from an organ that affects activity in other parts of the body. The function of erythropoietin is to stimulate the production of red blood cells. The kidney produces 85-95% of the body's erythropoietin so when the kidney is damaged (kidney disease or failure), not enough erythropoietin is produced to maintain normal red blood cell levels. This leads to anemia.
Anemia in Kidney Disease
Anemia is very common in people with kidney disease. Some causes of anemia can be dietary deficiencies of such nutrients as iron, folic acid (folate) and vitamin B12. Iron is an important component of hemoglobin, which is the oxygen carrying part of your red blood cell. Without iron, hemoglobin cannot be made and therefore your red blood cells look very pale and cannot carry oxygen to the tissues of your body. Anemia due to dietary deficiencies can be brought under control with dietary supplements.
Another cause of anemia in kidney disease is the lack of production of the hormone, erythropoietin. Erythropoietin is released into your blood by your kidneys when there is a low level of oxygen in your tissues. Erythropoietin travels to the bone marrow where it stimulates the production of red blood cells. When the kidneys do not function properly, they do not produce enough erythropoietin. This type of anemia will not be corrected by itself or through dietary supplements.
