Page 317 - Concise Pathology for Exam Preparation ( PDFDrive )

302 SECTION II Diseases of Organ Systems

Reduced urinary excretion (if kidney function is normal) indicates inadequate
vitamin B 12 absorption. Improved absorption with the subsequent addition of intrin-
sic factor to radiolabelled vitamin B 12 confirms the diagnosis of pernicious anaemia.
The test is often difficult to do or interpret because of incomplete urine collection or
renal insufficiency. In addition, because the Schilling test does not measure absorption of
protein-bound vitamin B 12 , the test does not detect defective liberation of vitamin B 12 from
foods, which is common among the elderly.
If the malabsorption is identified, the Schilling test can be repeated after a 2-week trial
of an oral antibiotic. If antibiotic therapy corrects malabsorption, the likely cause is intes-
tinal overgrowth of bacteria (eg, blind-loop syndrome).

Q. Write briefly on anaemia due to blood loss.
Ans.

Anaemia due to acute blood loss:
• A healthy adult tolerates a loss of about 500 mL of whole blood without any ill effects.
• When more is lost, compensatory mechanisms come into play (the blood flow to skin and
skeletal muscle is reduced, conserving the blood flow to vital organs like brain, kidney and
heart.) If bleeding continues, compensatory mechanisms fail and hypovolaemic shock
develops.
• Most expansion of plasma volume is seen in the first 24 h of blood loss.

Anaemia due to Chronic Blood Loss

Compensatory mechanisms replenish the plasma volume and red cell loss. However, if the
blood loss continues, body iron stores are depleted and anaemia due to iron deficiency appears.

Q. Define normocytic normochromic anaemia and enumerate its
causes.

Ans. Normocytic normochromic anaemia is characterized by normal size of RBCs
(normal MCV) and normal haemoglobinization (MCH).
Causes of normocytic normochromic anaemia are listed in Table 12.7.

TABLE 12.7. Causes of normocytic normochromic anaemia

Decreased red cell production Increased red cell loss
• Anaemia of chronic illness • Acute blood loss
• Marrow hypoplasia or aplasia • Hypersplenism
• Myeloproliferative diseases • Haemolytic disorders
• Myelofibrosis • Haemoglobinopathies (sickle cell disease)
• Chronic renal failure • Hereditary spherocytosis
• Chronic liver disease • Glucose-6-phosphate dehydrogenase deficiency
• Sideroblastic anaemia • Microangiopathic anaemias
• Hypothyroidism • Autoimmune haemolytic anaemia
• Adrenal insufficiency • Paroxysmal nocturnal haemoglobinuria

Q. Outline the pathogenesis and laboratory findings of anaemia of
chronic disease.
Ans. Anaemia of chronic disease is the most common cause of normocytic anaemia and
the second most common form of anaemia worldwide (after the iron-deficiency anaemia).
It occurs in a wide variety of chronic diseases including infective or inflammatory condi-
tions, neoplasms and collagen vascular disorders, eg, rheumatoid arthritis. The diagnosis
of anaemia of chronic disease is not usually applied to anaemias associated with renal,
hepatic or endocrine disorders.

mebooksfree.com