The day before a colonoscopy you can only have liquids, and you also have to drink a laxative to clear out your bowels.
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usage
Short for 结肠镜 'colonoscope' or 肠镜检查 'colonoscopy'; one has it done with 做. 镜 'mirror' names medical scopes, as in 胃镜 'gastroscopy'. A 无痛 'painless' colonoscopy is one done under sedation.