Anemia means that the hemoglobin level is too low.  Hemoglobin is the substance within red blood cells that carries oxygen. When hemoglobin gets low enough, the body tissues suffer from lack of oxygen and at very low hemoglobin levels this can lead to significant consequences.

A patient can become anemic for three main reasons – either they are losing blood somewhere, or they are not producing enough blood (bone marrow disorders), or the blood they are making is being destroyed (sometimes a reaction to medications or other problems).

Colorectal surgeons are often called upon to assist in the assessment of anemia since one of the most important causes of anemia is blood loss from hemorrhoids or a colorectal cancer.  Patients who become anemic from hemorrhoid bleeding will usually give a story of quite significant regular blood loss with bowel movements.  They will see the blood since it is originating just within the anal canal.  It will be bright red and obvious.  These patients need to have their hemorrhoids dealt with so they stop bleeding or bleed less.  Bleeding from a colorectal cancer can be less obvious.  A colorectal cancer can bleed slowly, and it can be higher up in the colon so that the small amounts of blood are not visible to the patient or the doctor.  This is known as ‘occult bleeding’.  Over time, occult bleeding results in a slow reduction of hemoglobin, leading to anemia.  Because it happens slowly, the patient adapts to the lowering hemoglobin and so it is often not until the anemia is profound that the patient begins to experience symptoms.  Some patients can lose half or more of their red blood cells before they notice something is wrong.  Patients who are anemic from blood loss are usually also iron deficient, since iron is part of the hemoglobin molecule and the ongoing bleeding will deplete their body’s iron stores.  A low iron (ferritin) blood level will distinguish the patient with blood loss anemia since patients with other causes of anemia will have a normal iron level.  Occult bleeding from a colorectal cancer can often be identified by FIT tests, although these tests do suffer from lack of accuracy.

© Pezim Clinic, Vancouver, British Columbia, Canada