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Diabetes mellitus

  • Clinically significant glucose intolerance
  • Chronic disease caused by absolute or relevant deficiency of insulin and therefore disorders of carbohydrate metabolism
  • Occurs in most species, most commonly in dog and cat
  • Predisposed to pancreatitis and may also have pancreatic insufficiency
  • Persistent increase in glucagon may cause hyperglycaemia

Aetiology

Can be caused by

  • Absolute deficiency of insulin due to degenerative changes in beta cells
  • Antagonism of insulin by hormones from the adrenal and thyroid glands, anterior pituitary causing high levels of blood glucose
  • Complication of pancreatic fibrosis
  • Insulin binding antibodies, insulinase and plasma antagonists imbalance
  • Chronic insulin resistance results in hyperinsulinism leading to islet exhaustion


Clinical signs

  • Hyperglycaemia
  • Polyuria
  • Polydypsia
  • Polyphagia
  • Weight loss
  • Muscle wasting (but some animals may present obese)
  • Hepatomegaly
  • Cataracts (dogs)
  • Later stages when becoming ketoacidotic
    • Dehydration
    • Depression
    • Inappetance
    • Vomiting
    • Diarrhoea
    • Ketotic breath
    • Ketonuria
    • Metabolic acidosis
  • Reduced cardiac output (due to loss of water and sodium), reduced blood pressure and renal flow causing circulatory collapse, coma and death

Pathology

  • Pancreas appers normal or reduced in size due to fibrosis
  • In cats, amyloidosis is sometimes present in the islets
  • Fatty change is consistently present in the liver and kidneys
  • The lens in the eye is often opaque due to deposition of sorbitol causing it to swell (glucose is converted into sorbitol once the glycolytic pathway is saturated)