Patients with a diagnosis of gastric cancer, trauma or other complications may require gastrectomy, which may often produce a condition called post gastrectomy syndrome that may include anaemia occurring as a result of vitamin $B_{12}$ malabsorption due to lack of intrinsic factor. Iron deficiency anaemia may also develop because removal of stomach often leads to marked decrease in production of gastric acid necessary to convert dietary iron to a form that is readily absorbed in duodenum.