Disorders of Absorption
Malabsorption - Failure of the intestinal processes of digestion, transport, or
both of nutrients across the intestinal mucosa into the systemic circulation
Malnutrition - A deficiency of nutrients such as energy, protein, vitamins and
minerals causes measurable adverse effects on tissue composition, function or
clinical outcome
Intestinal failure - A reduction in the functioning gut mass below the amount
required for adequate digestion and absorption of food. Types:
Type 1 – self limiting
o E.g. ileus after surgery
Type 2 – severe and requiring temporary support
o E.g. major resection, sepsis
Type 3 – chronic requiring long term nutritional support
o E.g. small bowel infarction
Mechanisms of absorption:
Luminal processing – carbohydrates, fats and proteins hydrolysed and
solubilised.
Mucosal absorption - Uptake of saccharides and peptides, lipids
processed and packaged for cellular export.
Transfer into circulation – Absorbed nutrients enter the vascular or
lymphatic circulation.
Where absorption can go wrong:
Luminal processing
o Surgery – inadequate mixing
o Pancreatic exocrine insufficiency
o Cholestasis – inadequate bile
Mucosal absorption
o Brush border defects – coeliac
o Inflammation – Crohn's disease
Transfer into circulation
o Lymphatic disease - lymphangiectasia
o Enterocyte processing – abetalipoproteinaemia
Malabsorption - Failure of the intestinal processes of digestion, transport, or
both of nutrients across the intestinal mucosa into the systemic circulation
Malnutrition - A deficiency of nutrients such as energy, protein, vitamins and
minerals causes measurable adverse effects on tissue composition, function or
clinical outcome
Intestinal failure - A reduction in the functioning gut mass below the amount
required for adequate digestion and absorption of food. Types:
Type 1 – self limiting
o E.g. ileus after surgery
Type 2 – severe and requiring temporary support
o E.g. major resection, sepsis
Type 3 – chronic requiring long term nutritional support
o E.g. small bowel infarction
Mechanisms of absorption:
Luminal processing – carbohydrates, fats and proteins hydrolysed and
solubilised.
Mucosal absorption - Uptake of saccharides and peptides, lipids
processed and packaged for cellular export.
Transfer into circulation – Absorbed nutrients enter the vascular or
lymphatic circulation.
Where absorption can go wrong:
Luminal processing
o Surgery – inadequate mixing
o Pancreatic exocrine insufficiency
o Cholestasis – inadequate bile
Mucosal absorption
o Brush border defects – coeliac
o Inflammation – Crohn's disease
Transfer into circulation
o Lymphatic disease - lymphangiectasia
o Enterocyte processing – abetalipoproteinaemia
