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Diarrhoea

Diarrhoea. Revision PBL. Definition. Diarrhoea is defined as: >3 bowel motions per day Looser than normal stools Stool volume > 300g May be associated with ugency. Types of diarrhoea. Secretory (non-invasive)

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Diarrhoea

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  1. Diarrhoea Revision PBL

  2. Definition • Diarrhoea is defined as: • >3 bowel motions per day • Looser than normal stools • Stool volume > 300g • May be associated with ugency

  3. Types of diarrhoea • Secretory (non-invasive) • Decreased intestinal absorption and increased intestinal secretion into the lumen resulting in watery diarrhoea • Commonly caused by: • Enterotoxins: eg cholera, E coli • Hormones: vasoactive intestinal peptide • Bile salts and fatty acids in the colon (following ileal resection) • Some laxatives (egdocusate sodium) • In watery diarrhoea, loss of fluids and salts often results in dehydration

  4. Types of diarrhoea • Invasive/Inflammatory • Caused by organisms invading the mucosa or inflammation primarily affecting the large bowel • This usually results in bloddy diarrhoea • There is also defective absorption of fluids & electrolytes • Common causes: • Infective conditions: dystenery due to Shigella and E Histiolytica • Inflammatory: UC and Crohn’s disease

  5. Types of diarrhoea • Osmotic • Caused by • generalised malabsorption so that high concentrations of solute remain in the lumen • Specific defect in absorption (eg disaccharide deficiency or glucose-galactosemalabsorption) • Ingested non-absorbed hypertonic substance (eg a purgative such as magnesium sulphate or Mg-containing antacid. • The volume of diarrhoea in this type is decreased by the absorption of fluid by the ileum & colon

  6. Types of diarrhoea • Abnormal motility • Generally of upper GIT so that frequency of defecation is high although volume is not (not true diarrhoea) • Caused by: • Diabetes • Removal of vagus nerve • Hyperthyroidism

  7. Common infections • Rotavirus • Self-limiting infection with watery diarrhoea • Shigella • Gram-negative bacteria causing abdominal cramping, high-grade fever and large volume watery diarrhoea lasting 3-7 days • Salmonella • Gram-negative anaerobes causing abdo cramping and self-limiting watery diarrhoea • Giardia • Protozoan parasite, water-borne causing acute and chronic watery diarrhoea, malabsorption, weight loss and abdo cramping • Other causes • staphylococcus, campylobacter jejuni, clostridium, Escherichia coli, adenoviruses, etc.

  8. Drug treatment • Rehydration is the most important therapy for diarrhoea! • Antibiotics for infective diarrhoea • Anti-diarrhoeal agents • Decreases gut motility • Muscarinic receptor antagonists – reduce spasms (e.g. Atropine) • Opiates (reduce motility) – main ones are codeine, diphenoxylate, loperamide • Loperamide – selective for GI tract, does not cross BBB, less SE

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