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Laboratory investigations

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

  • barium enema to test for cathartic colon - ahaustral right colon.
  • sigmoidoscopy - may see melanosis coli (microscopic form is often the normal variant).
  • alkalinisation of stool: phenolphthalein, some anthraquinones, and rhubarb turn red; bisacodyl turns purple-blue.
  • thin-layer chromatography or spectrophotometry of urine or stool water: detects anthraquinones, bisacodyl, phenolphthalein

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