Page 38 - Gastrointestinal Bleeding (Xuất huyết tiêu hóa)

312 PART III Symptoms, Signs, and Biopsychosocial Issues

deficiency is especially important. The duodenum is the site of blood in the stool. They often have extremely low body stores of
iron absorption in the small intestine. Most dietary iron is in the iron and require IV iron supplementation (see Chapter 8).
ferric form, but only the ferrous form of iron can be absorbed by The differential diagnosis of iron deficiency anemia includes
the duodenum. Ascorbic acid at a low pH is required to release anemia of chronic disease and thalassemia. In anemia of chronic
nonheme iron and convert it to the ferrous form for absorption disease, both the serum iron level and TIBC are low, with a nor-
in the small intestine. 387 Several studies have shown that 20% to mal serum ferritin level. Patients with thalassemia have a family
30% of patients with iron deficiency anemia have gastric atrophy history of anemia, splenomegaly, target cells on peripheral blood
and therefore do not produce an acid milieu that facilitates iron smear, and normal serum ferritin levels.
absorption. 383,388,389 Iron deficiency anemia has also been associ- Patients with unexplained iron deficiency anemia should
ated with Hp infection. 390 Therefore gastric biopsies should be undergo EGD and colonoscopy to rule out a GI tract lesion
obtained during upper endoscopy in patients with unexplained that may cause chronic blood loss. In a prospective study of 100
iron deficiency anemia (see Chapters 52, 53, and 103). patients with iron deficiency anemia, GI tract lesions were found
Celiac disease commonly manifests as iron deficiency anemia, in 62 patients, with 36 having lesions in the UGI tract (mostly
primarily because of iron malabsorption resulting from blunted ulcers), 25 in the colon (mostly cancer), and 1 in both the UGI
duodenal villi. Patients with celiac disease have been reported to tract and colon. 393 In patients with unexplained iron deficiency
have higher rates of positive FOBT results than healthy controls, anemia who undergo EGD, duodenal biopsy specimens should
but subsequent studies in which radiolabeled RBCs were used be obtained to exclude celiac disease as a cause of iron malab-
did not find a true increase in blood loss. 391,392 The cause of iron sorption. Gastric biopsy samples also should be obtained to rule
deficiency anemia in patients with celiac disease may, in fact, be out gastropathy and Hp infection. Depending on the severity of
multifactorial. Any patient who is evaluated for iron deficiency iron deficiency anemia, even without a positive FOBT result,
anemia and undergoes EGD should have duodenal biopsy sam- evaluation of the small intestine for a bleeding lesion, as discussed
ples obtained to look for celiac disease (see Chapter 107). earlier, should be considered. If a specific cause of anemia is not
Patients who have undergone Roux-en-Y gastric bypass sur- identified, patients should be advised to avoid antiplatelet and
gery are at high risk of iron malabsorption because of bypass of anticoagulant drugs and take supplemental iron.
the duodenum, where most iron is absorbed. These patients can
present with severe unexplained iron deficiency without occult Full references for this chapter can be found on www�expertconsult�com