Hypoalbuminaemia

Description

Hypoalbuminaemia refers to a reduced blood level of albumin, one of the major plasma proteins which is synthesised in the liver. Albumin has multiple physiological functions including exertion of 75% of the total plasma oncotic pressure (to prevent leakage of fluid into body cavities and the interstitium), carriage of drugs and hormones in the blood (particularly thyroid and reproductive hormones and non-steroidal anti-inflammatory drugs, thiopental sulphate and frusemide) and buffering of blood pH changes. Albumin has a circulating half-life of 17-19 days.

Causes of Hypoalbuminaemia

The synthesis of albumin may be reduced or it may be lost in greater quantities than normal:

• Reduced synthesis of albumin
  • Severe malnutrition resulting in the inability to synthesise sufficient albumin
  • Acute phase response, in which the production of positive acute phase proteins is favoured at the expense of negative acute phase proteins like albumin and transferrin. Globulins will be elevated in this response, with a reduced albumin: globulin ratio.
  • Severe hepatic damage, as in chronic liver failure, cirrhosis or with congenital porto-systemic shunts.
• Increased loss of albumin
  • Severe exudates that contain large quantities of protein may deplete the plasma proteins:
    • Dermal protein loss with severe thermal or chemical burns.
    • Septic peritonitis with exudative peritoneal fluid.
  • Protein-losing enteropathy (PLE) caused by inflammatory bowel disease, lymphangiectasia or alimentary lymphoma. Globulins and, in severe cases, whole blood are lost with albumin in this condition.
  • Protein-losing nephropathy (PLN) caused by primary glomerulopathy, glomerulonephritis or amyloidosis. Albumin, having a smaller molecular weight, is lost in great excess of globulin. Severe PLN results in Nephrotic Syndrome characterised by severe hypoproteinaemia, hypercholesterolaemia and ascites, hydrothorax and subcutaneous oedema.
  • Acute haemorrhage followed by autotransfusion (movement of fluid into the circulation from the interstitium) will result in dilution of the remaining plasma proteins.
• Apparent hypoalbuminaemia may occur in overhydrated or hypervolaemic animals suffering from primary (pyschogenic) polydipsia or which have received intra-venous fluid therapy.