Understanding Anemia in Chronic Kidney Disease

Many patients with chronic kidney disease (CKD) learn of their anemia because they feel weak and fatigued, or they are informed by their doctor. An informative article written by Stephen Z. Fadem, MD, FACP, answers some important questions to help patients assess whether they may be anemic.

Anemia is defined as a low red blood cell count. Since the red blood cells contain a molecule known as hemoglobin, we simply measure its concentration. If the amount of hemoglobin is less than 12 grams, the patient is said to be anemic. If the value is less than 11 grams, treatment is generally required.

It is not intuitive to think that the kidney, an organ better known for its production of urine, also plays a role in regulating the amount of red cells in the body. In nature, the amount of oxygen in the blood determines how fast red cells are produced. Low oxygen content in kidney cells stimulates the genes inside their center (nucleus) to synthesize the hormone necessary to turn on the bone marrow so it can produce red blood cells. If the oxygen content is high, then the factors that stimulate this process are automatically destroyed and recycled in kidney cells before they have a chance to perform their genetic magic. This keeps the system balanced, but always, some of the factor is able to get through to the genetic machinery of the kidney cell and produce the stimulating hormone.

This hormone is called erythropoietin (EPO). When it is produced by the kidney, it travels to the bone marrow and turns on the mechanisms that help red blood cells mature. Without EPO, the production of red cells is diminished.

As the kidney becomes progressively diseased, mechanisms that form scar tissue take over, and with the process of scarring, cells responsible for manufacturing EPO die. These are the same cells that are under feedback control that increase in the face of hypoxia (lack of oxygen reaching body tissues) and decrease EPO production with enriched oxygen. Now, faced with becoming extinct, the production of EPO sharply decreases.

To read this article in its entirety, including signs and symptoms of anemia, please visit http://www.aakp.org/aakp-library/Anemia-in-Chronic-Kidney-Disease/index.cfm

This article originally appeared in the December 2005 issue of Kidney Beginnings:
The Magazine, Vol. 4, No. 5.