Section J: Hematology

Anemia

BACKGROUND

The initial evaluation of a child with anemia is a common task for general pediatricians or hospitalists. Defined as insufficient red blood cell (RBC) mass for the age of the patient, anemia can develop acutely or insidiously. In children, anemia that develops gradually over several weeks to months may be profound but with little clinical consequence other than obvious pallor. However, if anemia develops acutely, the patient has no time to compensate for decreased oxygen carrying capacity, and symptoms of anemia (ranging from fatigue to cardiovascular collapse) can develop rapidly. Because anemia can result from many disease processes, it is helpful to divide anemia into broad pathophysiologic categories: (1) decreased production of either hemoglobin or RBCs, (2) premature RBC destruction, or (3) blood loss.¹ Fortunately, distinguishing among these processes usually requires only basic, widely available laboratory tests. Once the pathophysiologic category is determined, the differential diagnosis narrows, and the evaluation is much less daunting. This chapter focuses primarily on children with newly recognized anemia for whom the evaluation is often initiated by pediatric hospitalists.

CLINICAL PRESENTATION

Anemia is often discovered incidentally during laboratory screening for other indications in a child who otherwise exhibits no symptoms of anemia.^2-4 Systematic evaluation of febrile hospitalized children demonstrated that a majority may exhibit mild anemia.^5,6 Alternatively, pallor and fatigue, the cardinal symptoms of anemia, may bring the patient to medical attention. Severe anemia, especially when there is a rapid onset, may present with weakness, obtundation, syncope, exertional dyspnea, congestive heart failure, or shock.

The probable causes of anemia can often be predicted by considering the age of the patient and taking a careful history. A directed history should thoroughly review the child’s diet, including the amount and type of milk, red meat, fruits, and vegetables consumed daily, as well as a history of pica. Growth and development, blood loss (i.e. melena, hematemesis, hemoptysis, hematuria), and recent illnesses are also important areas of inquiry. Acute and/or chronic inflammation often are underlying causes of anemia in hospitalized patients. Because many causes of anemia are inherited, the family history is critical and should include questions about transfusions, bleeding, splenectomy, cholelithiasis or cholecystectomy, and prior diagnoses of anemia.

The physical examination should focus on manifestations of anemia and diagnostic clues. Tachycardia, systolic murmur, and pallor suggest a moderate degree of anemia. Severe anemia can be accompanied by symptoms of congestive heart failure and tachypnea, despite children’s typically profound and effective cardiovascular compensatory mechanisms. Jaundice or dark urine suggests intravascular hemolysis and rapidly narrows the differential diagnosis. Similarly, hepatosplenomegaly, a physical sign of great importance in the diagnostic evaluation of an anemic patient, suggests extramedullary hematopoiesis (as in chronic hemolytic anemias) or other diagnoses (e.g. storage diseases, bone marrow infiltration, infections).

The initial laboratory evaluation typically includes a basic panel of hematologic studies, ...