Anemia and chronic kidney disease

What is anemia?

Anemia is a condition in which the body has fewer red blood cells than normal. Red blood cells carry oxygen to tissues and organs throughout the body and enable them to use energy from food. With anemia, red blood cells carry less oxygen to tissues and organs — particularly the heart and brain — and those tissues and organs may not function as well as they should.

How is anemia related to chronic kidney disease?

Anemia commonly occurs in people with chronic kidney disease (CKD) — the permanent, partial loss of kidney function. Anemia might begin to develop in the early stages of CKD, when someone has 20 to 50 percent of normal kidney function. Anemia tends to worsen as CKD progresses. Most people who have total loss of kidney function, or kidney failure, have anemia. A person has kidney failure when he or she needs a kidney transplant or dialysis in order to live. The two forms of dialysis include hemodialysis and peritoneal dialysis. Hemodialysis uses a machine to circulate a person’s blood through a filter outside the body. Peritoneal dialysis uses the lining of the abdomen to filter blood inside the body.

What causes anemia in chronic kidney disease?

The most common causes of anemia are:

  • Loss of blood through surgery, accidents and other causes
  • Conditions such as chronic kidney disease, liver disease, cancer, HIV/AIDS
  • Not enough iron, vitamin B12 or folic acid
  • A poor diet
  • Diseases that destroy red blood cells, such as sickle cell anemia

When kidneys are diseased or damaged, they do not make enough EPO. As a result, the bone marrow makes fewer red blood cells, causing anemia. When blood has fewer red blood cells, it deprives the body of the oxygen it needs.
Other common causes of anemia in people with kidney disease include blood loss from hemodialysis and low levels of the following nutrients found in food:

  • Iron
  • Vitamin B12
  • Folic Acid

These nutrients are necessary for red blood cells to make hemoglobin, the main oxygen-carrying protein in the red blood cells.

If treatments for kidney-related anemia do not help, the health care provider will look for other causes of anemia, including:

  • Other problems with bone marrow
  • Inflammatory problems — such as arthritis, lupus, or inflammatory bowel disease — in which the body’s immune system attacks the body’s own cells and organs
  • Chronic infections such as diabetic ulcers
  • Malnutrition

Healthy kidneys produce a hormone called EPO. EPO prompts the bone marrow to make red blood cells, which then carry oxygen throughout the body. When the kidneys are diseased or damaged, they do not make enough EPO. As a result, the bone marrow makes fewer red blood cells, causing anemia.

Different types of anemia and their causes include:

  • Iron deficiency anemia. This is the most common type of anemia worldwide. Iron deficiency anemia is caused by a shortage of iron in your body. Your bone marrow needs iron to make hemoglobin. Without adequate iron, your body can’t produce enough hemoglobin for red blood cells. Without iron supplementation, this type of anemia occurs in many pregnant women. It is also caused by blood loss, such as from heavy menstrual bleeding, an ulcer, cancer and regular use of some over-the-counter pain relievers, especially aspirin.
  • Vitamin deficiency anemia. In addition to iron, your body needs folate and vitamin B-12 to produce enough healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. Additionally, some people may consume enough B-12, but their bodies aren’t able to process the vitamin. This can lead to vitamin deficiency anemia, also known as pernicious anemia.
  • Anemia of chronic disease. Certain diseases — such as cancer, HIV/AIDS, rheumatoid arthritis, kidney disease, Crohn’s disease and other chronic inflammatory diseases — can interfere with the production of red blood cells.
  • Aplastic anemia. This rare, life-threatening anemia occurs when your body doesn’t produce enough red blood cells. Causes of aplastic anemia include infections, certain medicines, autoimmune diseases and exposure to toxic chemicals.
  • Anemias associated with bone marrow disease. A variety of diseases, such as leukemia and myelofibrosis, can cause anemia by affecting blood production in your bone marrow. The effects of these types of cancer and cancer-like disorders vary from mild to life-threatening.
  • Hemolytic anemias. This group of anemias develops when red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases increase red blood cell destruction. You can inherit a hemolytic anemia, or you can develop it later in life.
  • Sickle cell anemia. This inherited and sometimes serious condition is an inherited hemolytic anemia. It’s caused by a defective form of hemoglobin that forces red blood cells to assume an abnormal crescent (sickle) shape. These irregular blood cells die prematurely, resulting in a chronic shortage of red blood cells.
  • Other anemias. There are several other forms of anemia, such as thalassemia and malarial anemia.

CKD and anemia

So why is anemia a common problem for people with chronic kidney disease? Because renal disease can cause low levels of erythropoietin and/or iron in the body.

Healthy kidneys produce a hormone called erythropoietin, or epo for short. When the body senses low oxygen levels, it tells the kidneys to release epo. This hormone tells your bone marrow to make more red blood cells. More red blood cells in the bloodstream mean more oxygen can be transported. However, if the kidneys are damaged, they may make little or no epo.

Iron is a mineral found in protein-rich foods that helps make hemoglobin, the protein in the red blood cell that carries oxygen. A major source of iron is red meat. Because patients in the early stages of kidney disease are advised to reduce the amount of protein they eat, they may not be getting adequate amounts of iron from their diet.

The buildup of waste in the bloodstream can also affect red blood cells. Healthy kidneys filter toxins from the bloodstream but kidneys affected with chronic kidney disease are unable to filter as well as they should. Because the body is unable to get rid of this waste, it remains in the bloodstream where it can shorten the lifespan of the existing red blood cells.

Anemia can develop in the early stages of kidney disease and get worse as renal disease progresses. Nearly all patients in end stage renal disease (the point where dialysis becomes necessary) have anemia.

How is anemia in chronic kidney disease diagnosed?

A health care provider diagnoses anemia based on

  • A medical history
  • A physical exam
  • Blood tests

Medical History

Taking a medical history is one of the first things a health care provider may do to diagnose anemia. He or she will usually ask about the patient’s symptoms.

Physical Exam

A physical exam may help diagnose anemia. During a physical exam, a health care provider usually examines a patient’s body, including checking for changes in skin color.

Blood Tests

To diagnose anemia, a health care provider may order a complete blood count, which measures the type and number of blood cells in the body. A blood test involves drawing a patient’s blood at a health care provider’s office or a commercial facility. A health care provider will carefully monitor the amount of hemoglobin in the patient’s blood, one of the measurements in a complete blood count.

The Kidney Disease: Improving Global Outcomes Anemia Work Group recommends that health care providers diagnose anemia in males older than age 15 when their hemoglobin falls below 13 grams per deciliter (g/dL) and in females older than 15 when it falls below 12 g/dL. If someone has lost at least half of normal kidney function and has low hemoglobin, the cause of anemia may be decreased EPO production.

Two other blood tests help measure iron levels:

  • The ferritin level helps assess the amount of iron stored in the body. A ferritin score below 200 nanograms (ng) per milliliter may mean a person has iron deficiency that requires treatment.
  • The transferrin saturation score indicates how much iron is available to make red blood cells. A transferrin saturation score below 30 percent can also mean low iron levels that require treatment.

In addition to blood tests, the health care provider may order other tests, such as tests for blood loss in stool, to look for other causes of anemia.

How is anemia treated in CKD patients?

Depending on the cause of your anemia (low epo levels, low iron levels or a combination of both), your doctor will prescribe medication or supplements, including EPOGEN or Procrit, which will add to the amount of erythropoietin your body makes naturally. Your doctor may also have you take iron supplements, especially if you’re taking EPOGEN or Procrit, for them to work effectively.

If you’re not getting enough iron, your doctor will refer you to a renal dietitian. Together, you will work on a meal plan that will include kidney-friendly foods rich in iron, vitamin B12 and folic acid.

Your kidney doctor will monitor your condition and make any changes to your treatment plan as necessary. Discuss any concerns or questions you have with your doctor and your renal dietitian before taking over-the-counter iron tablets, multi-mineral or B vitamins or making any changes to your eating plan.

How is anemia in chronic kidney disease treated?

Depending on the cause, a health care provider treats anemia with one or more of the following treatments:

Iron

The first step in treating anemia is raising low iron levels. Iron pills may help improve iron and hemoglobin levels. However, for patients on hemodialysis, many studies show pills do not work as well as iron given intravenously.

Erythropoietin

If blood tests indicate kidney disease as the most likely cause of anemia, treatment can include injections of a genetically engineered form of EPO. A health care provider, often a nurse, injects the patient with EPO subcutaneously, or under the skin, as needed. Some patients learn how to inject the EPO themselves. Patients on hemodialysis may receive EPO intravenously during hemodialysis.

Studies have shown the use of EPO increases the chance of cardiovascular events, such as heart attack and stroke, in people with CKD. The health care provider will carefully review the medical history of the patient and determine if EPO is the best treatment for the patient’s anemia. Experts recommend using the lowest dose of EPO that will reduce the need for red blood cell transfusions. Additionally, health care providers should consider the use of EPO only when a patient’s hemoglobin level is below 10 g/dL. Health care providers should not use EPO to maintain a patient’s hemoglobin level above 11.5 g/dL. Patients who receive EPO should have regular blood tests to monitor their hemoglobin so the health care provider can adjust the EPO dose when the level is too high or too low. Health care providers should discuss the benefits and risks of EPO with their patients.

Many people with kidney disease need iron supplements and EPO to raise their red blood cell count to a level that will reduce the need for red blood cell transfusions. In some people, iron supplements and EPO will improve the symptoms of anemia.

Red Blood Cell Transfusions

If a patient’s hemoglobin falls too low, a health care provider may prescribe a red blood cell transfusion. Transfusing red blood cells into the patient’s vein raises the percentage of the patient’s blood that consists of red blood cells, increasing the amount of oxygen available to the body.

Vitamin B12 and Folic Acid Supplements

A health care provider may suggest vitamin B12  and folic acid  supplements for some people with CKD and anemia. Using vitamin supplements can treat low levels of vitamin B12 or folic acid and help treat anemia. To help ensure coordinated and safe care, people should discuss their use of complementary and alternative medical practices, including their use of dietary supplements, with their health care provider.

Eating, Diet, and Nutrition

A health care provider may advise people with kidney disease who have anemia caused by iron, vitamin B12, or folic acid deficiencies to include sources of these nutrients in their diets. Some of these foods are high in sodium or phosphorus, which people with CKD should limit in their diet. Before making any dietary changes, people with CKD should talk with their health care provider or with a dietitian who specializes in helping people with kidney disease. A dietitian can help a person plan healthy meals.

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