Differentials

Question 1

Causes of Metabolic Acidosis

with Normal Anion gap

with high Anion gap

Answer 1

NORMAL ANION GAP

↑GI Bicarbonate loss: diarhhoea, fistula, ileostomy

Type 1 renal tubular acidosis: ↓H+ secretion in distal tubules

Type 2 RTA: ↓HCO3- absorptio proximal renal tubules

Type 4 RTA: ↓ ammonia excretion caused by hyperkalaemia secondary to hypoldosteronism (1ary or 2ndary)

Amonium chloride ingestion

HIGH ANION GAP

1. Ketoacidosis: diabetes T1, starvation, alcoholism
2. Lactic acidosis:

• Tissue hypoxia
• Drugs: Metformin, alcohol, methanol, ethylene glycol, zidovudine
• Short gut syndrome
• Leukemia
• Lymphoma
• Liver failure
• Glucose-6-phosphatase deficiency

3. Renal failure

4. Slaycilate poisoning

Question 2

Causes of respiratory acidosis

Answer 2

CNS:

organic causes (tauma, vascualr events etc)

Drugs

Lungs: severe asthma, COPD etc

Neuromuscular:

Guillain-Barre

Severe kyphoscoliosis

Question 3

Alkalosis

Answer 3

Metabolic

GI loss of H+

Renal loss of H+

Hyperaldosteronism

Excess glucocorticoids: Cushing’s

Thiazide diuretics, loop diuretics

Intracellular shift of H+ due to hypokalaemia

Question 4

Causes of macrocytic anaemia

Answer 4

1. Alcohol
2. Foalte/B12 deficiency
3. Haemolytic anaemia
4. Hypothyroidism
5. Liver disease
6. Myelodysplasia
7. Drugs: methotrexate, zidovudine, hydroxyurea

Question 5

Causes of Microcytic anemia

Answer 5

Fe deficiency

THalassemia

Sideroblastic anaemia

Lead poisoning

Anaemia of chronic disease (often normocytic)

Question 6

Causes of normocytic anaemia

Answer 6

1. Anaemia of chronic disease
2. Haemolytic disease
3. Hypothyroidism
4. Pregnancy
5. Renal failure
6. Bone marrow failure