What is the cause of colon cancer?

How does colon cancer cause iron deficiency anaemia?

• Iron deficiency anaemia, is a common finding in colon cancer, but how does it occur? What is the pathology behind it? Is it just because of occult blood loss? Thanks :)

• Answer:

  Yes, it is because of occult blood loss. People have usually been losing blood for a long time before they figure out they have colon cancer. To address the other answer... Iron deficiency anemia is caused by inadequate amounts of iron in the body. That is how it is diagnosed. Anemia of chronic disease (which is common in many types of cancer) is caused by inadequate utilization of iron--that is, there is enough iron in the body, it simply isn't being used. Trying to determine whether or not anemia of chronic disease is occurring in the setting of iron deficiency anemia (due to occult blood loss) is a useless exercise because (1) there is no way to tell if it is happening or not, and (2) impaired utilization of iron is trumped by not having enough iron in the first place (i.e., if you could hypothetically fix the impaired utilization, it wouldn't help because you are still iron deficient). Furthermore, I am not aware of any evidence in the scientific literature that colon cancer has any significant adverse effects on the intestinal flora (I've looked). With regards to those specific vitamins...I am not aware that K had anything to do with red blood cell production. Vitamin K is needed for proper blood clotting and a deficiency could result in worse occult bleeding. Vitamins B6 and B12 are largely absorbed in the small intestine, so you would have to explain why a tumor in the colon would affect this. People can develop nutrient deficiencies *after* surgical resection of the tumor because you've removed parts of the intestinal tract that may be necessary to absorb those nutrients. But that is a whole different issue.