VPP 211: General Veterinary Pathology (1+1)

CALCIFICATION

Calcification is abnormal deposition of calcium salts in tissue other than bone.

• Calcium is normally present in blood and deposited in bones. Calcium if deposited in an abnormal tissue with normal or abnormal blood calcium level is considered as pathological condition.
• Pathological calcifications are
  • Metastatic calcification
  • Dystrophic calcification

Metastatic calcification

• Deposition of calcium occurs in soft tissue following increase in the blood calcium (Hypercalcaemia i.e. .12 mg/dL). Hypercalcaemia may arise due to
  • Parathyroid tumour in which high levels of parathormone favours phosphate excretion through kidneys (hyperphosphaturia), hypophosphataemia and withdrawal of calcium from bones.
  • Primary and secondary bone tumours cause rarefaction of bone.
  • Nutritional cause with high vitamin D intake resulting in increased absorption of calcium.
  • Renal disease with retention of phosphate, hypophophosphaturia, depression of calcium, parathyroid stimulation and hypercalcaemia.
• Wherever acid is secreted calcium deposition occurs. e.g. Stomach-HCl; Kidneys-Hippuric acid; Lungs-CO₂.

Dystrophic calcification

Dystrophic calcification is calcification of abnormal tissue with normal blood calcium levels.e.g. Necrotic tissues (Tuberculous lesion, suppurative lesion, renal tubular epithelial cells in mercurial poisoning), scar tissue, dead parasites, atherosclerotic plaques, old thrombi

• Pathogenesis
  • Deposition of calcium occurs around the nidus. The phosphates from the dead tissues form the nidus. Further, the calcium combines with phosphates to form calcium soaps .
• Gross lesions
  • Hard, gritty mass and on section gritty sound is heard. Usually lesions are microscopical.

Calcifies nodule - TB - mesenteric lymph node

• Microscopic lesion
  • Calcified areas take up a blue colour with H&E stain and black with von Kossa stain