Before a colonoscopy or surgery

In the days before a colonoscopy or bowel surgery, the aim is to leave as little as possible behind in the bowel. Residue obscures the view during a colonoscopy and gets in the way during an operation. So the diet narrows for a short, defined period, usually one to three days, and then stops.

What the guidance emphasises

Following your own hospital's instruction sheet exactly, because this is the one part of the diet where the details are set by the unit doing the procedure and where they differ. The number of days varies. Some units ask for clear fluids only for the final stretch. Most give a specific time to stop eating, a bowel preparation solution to drink, and a schedule for it.

There is real variation in how long the restriction runs. UK protocols commonly ask for two or three days. Updated consensus discussed in the international literature suggests a single day of restriction may work as well, and some units have moved that way.

This is also the best-evidenced use of low-fibre eating anywhere in this book. Several systematic reviews find that a low-residue diet before a colonoscopy gives a view as good as clear fluids alone, with less hunger and nausea and more willingness to go through it again. Everything else in the evidence is thinner than this.

What this book does

Recipes tagged for before a colonoscopy or surgery are the plainest and lowest-residue in the book, and several are drinks or broths for the last day when eating stops. Nothing here overrides your hospital's sheet. If the two disagree, the sheet wins, because the procedure is theirs.

How long

One to three days, ending at the time your hospital has given you. There is no stepping back up to plan afterwards. Normal eating resumes once the procedure is done and you are told it can.

If you cannot keep the bowel preparation down, or if you have severe pain, vomiting or bleeding while taking it, ring the endoscopy or surgical unit on the number on your appointment letter rather than working it out from a recipe.