Megaloblastic anemia, associated with surgically produced gastrointestinal abnormalities.

Two of the mechanisms for vitamin B(12) deficiency, leading to megaloblastic anemia, are the result of surgically produced abnormalities of the gastrointestinal tract. The basic mechanism is different for each lesion. Total gastrectomy results in complete lack of intrinsic factor which is necessary for vitamin B(12) absorption. It is believed that if patients survive long enough and are not given prophylactic vitamin B(12) therapy, all would develop megaloblastic anemia. Intestinal anastomosis leading to stasis of intestinal contents, with overgrowth of bacteria may cause vitamin B(12) deficiency through bacterial interference with the utilization of vitamin B(12). Use of radioactive vitamin B(12) (cobalt(60)-labeled B(12)) has led to a better understanding of the pathogenesis of both types of megaloblastic anemia. The radioactive vitamin provides a useful tool for study of its absorption from the gastrointestinal tract.