Introduction
Red blood cells are produced in the bone marrow in response to stimulation by erythropoeitin (EPO), a hormone produced by the kidneys. Advanced kidney disease causes anemia, a low red blood cell (RBC) count, by decreasing the production of EPO. Fortunately, a synthetic version of this hormone is available (Epoetin) and most people with advanced kidney disease (>95%) will respond to it.
Common Causes for a Poor Response
Most people can achieve a good response to EPO and if they don’t, it is most likely due to one or more of the following cause:
- Iron Deficiency: The most common cause of patients not responding to EPO. Iron is a critical component of hemoglobin, which is a major component of red blood cells.
- Chronic Blood Loss: An important cause of iron deficiency and inadequate response to EPO. Any person with falling blood counts, increasing EPO requirements, or continued iron deficiency despite iron replacement should be evaluated for ongoing blood loss.
- Infection / Inflammation: Any infection or inflammatory response can dramatically reduce the effectiveness of EPO. The exact cause is not known but it is thought by many to be a form of defense against invasion by foreign organisms.
- Osteitis Fibrosa: Advanced kidney disease is associated with elevated levels of a hormone produced by the parathyroid glands (iPTH). An elevated iPTH can cause bone to “turn over” very quickly leading to scarring of the bone marrow. This scarring prevents the bone marrow from adequately responding to EPO to make red blood cells.
- Aluminum Toxicity: Advanced kidney disease leads to difficulty in removing excess phosphorus from the body. Most patients require some sort of "binder” to keep them from being absorbed in the gut from the diet. Binders containing aluminum can be very effective in decreasing phosphorous levels but they also can cause aluminum to collect in the bones and disrupt red blood cell production.
Referral To a Hematologist
If none of the above conditions are found to be the cause, a referral to a blood specialist (hematologist) may be indicated. The hematologist will order special tests, look at your blood under a microscope, and possibly perform a bone marrow biopsy. The goal will be to assess for (among many other potential causes) the following:
- Deficiencies in vitamins such as folate and/or vitamin B12
- Increased red cell destruction which is called hemolysis
- Hereditary diseases such as sickle cell anemia or thallasemia
- Cancerous conditions such as myeloma, leukemia, or myelodysplasia
No Reversible Cause Is Found
If no treatable cause is ultimately found, alternative therapies are available (such as carnitine, androgens or increasing the amount dialysis). Unfortunately, these treatments are often not effective and it is likely that the lower blood count will have to be accepted or periodic blood transfusions be given.
