Disorders Of Absorption Notes

Lecture 16

Disorders of absorption

• Definitions

  • Malabsorption

    • Failure of intestinal processes of digestion, transport, or both of nutrients across intestinal mucosa into systemic circulation

  • Malnutrition

    • Outcome of Malabsorption

    • Deficiency of nutrients such as energy, protein, vitamins &minerals causes measurable adverse effects on tissues, function or clinical outcome

• Mechanisms of absorption

  • Three types

    • Luminal processing

      • Carbs, fats and proteins hydrolysed and solubilised (pancreatic & bilary action)

    • Mucosal absorption

      • Uptake of saccharides and peptides, lipids processed and packaged for cellular export

    • Transfer into circulation

      • Absorbed nutrients enter vascular or lymphatic circulation

  • Where can it go wrong?

    • Luminal processing

      • Surgery- inadequate mixing

      • Pancreatic insufficiency

      • Cholestasis- inadequate bile (blockage of duct- stones, cancer etc.)

    • Mucosal absorption

      • Brush border defects- coeliac

      • Inflammation- Crohns

    • Transfer into circulation

      • Lymphatic disease- lymphangiectasis

      • Enterocyte processing- abetalipoproteinaemia

        • Rare, autosomal recessive. Cannot transmit fats properly

• Signs and symptoms

  • General

    • Varied presentation

    • Multiple systems affected

    • Depends upon underlying aetiology

    • Can be asymptomatic

  • Presenting features

    • Pain & bloating

      • Inflammation or obstruction (Crohns)

      • Bacterial fermentation & gaseous distension (norm gut flora change)

    • Weight loss

      • Often indicates small bowel pathology

      • Dietary avoidances (e.g. fatty food may give diarrhoea etc.)

    • Diarrhoea (commonest)

      • Secretory diarrhoea (inflammatory conditions)

      • Fat Malabsorption (steatorrhoea)

      • Bile salt malabsorption (failure to reabsorb back into blood)

    • Anaemia

      • May be asymptomatic

      • Fe deficiency

      • B12 deficiency (Microcytic/Megaloblastic anaemia)

      • Folate deficiency (Microcytic/Megaloblastic anaemia)

    • Miscellaneous

      • Neurological e.g. B12 deficiency, Ca2+ deficiency (Trousseau’s)

      • Bleeding e.g. vitamin K deficiency

      • Metabolic e.g. bone fractures

• Important causes of malabsorption

  • Loss of surface area (80-120cm= minimum small intestine needed)

    • Resection

    • Fistula (abnormal joining between mucosal surfaces e.g. duodenum to colon, bypasses small bowel= loss of surface area)

    • Coeliac disease

    • Inflammation

      • Crohn’s, radiation enteropathy, ischaemia, infection

• Specific diseases

  • Crohn’s disease

    • General

      • Chronic relapsing condition

      • Transmural inflammation

      • Causes malabsorption through small bowel inflammation or fistula

      • Aetiology- combo genetic & environment (microbes, smoking etc.)

      • Can affect any part of gut from mouth...

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