laboratory investigations
Last reviewed 01/2018
- 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