Bowel Preparation

Lifestyle Preventative Health and Medications > Bowel Preparation

Bowel Preparation

Bowel Preparation 

Bowel preparation is an essential part of getting ready for a colonoscopy (an inspection of your colon with an endoscope). It involves taking a special diet for a few days prior to the procedure, together with special bowel cleansing medication taken 1 day before/ on the day, to clear your bowel of any faecal material. As the patient, you play this important role in cleansing your bowel of faecal material so that the colonoscopy can be done both in a safe manner, and to allow good visualization of the colon.

Imagine trying to drive a car with mud on the windscreen – if there is retained faecal material, this can result in poor visibility. This may make the colonoscopy both unsafe and may result in colonic polyps or other suspicious colonic lesions being missed. If there is poor visibility due to a retained faecal material, the doctor performing the colonoscopy may decide to cancel, postpone or repeat the procedure at a later date.

Dietary Advice 

You will be asked to take a low residue diet a few days prior to the colonoscopy. The low residue is designed to be easy to digest, resulting in a lowered stool volume that is easy to pass. It is generally low in fibre and avoid food that remains undigested such as seeds. The following is a list of low residue foods (to take) and a list of high residue foods (to avoid), for a few days prior to endoscopy.

Table 1: Low Residue and high residue foods

Low Residue foods (To Take) High Residue foods (To Avoid)
Vegetables and fruits:
Take well-cooked fresh vegetables without seeds
✔Green beans
✔Cooked potatoes without skin
✔Tomato sauce
✔Canned fruits without the skin (e.g apple puree)
✔Vegetable of fruit juices without seeds or pulp

✔Meat does not have fibre, so taking beef, lamb, chicken or fish is fine.
But make sure they are lean (without fat), tender, and not in large pieces.
✔Avoid smoked or cured meats.

✔White rice/porridge
✔Pasta (with less than 1 gram of fibre per serving)

Fats & Oils:
✔Butter, margarine, cream, mayonnaise
✔Cream-based soups

Vegetables and fruits to avoid:
❌Bean sprouts
❌Leafy vegetables
❌Raw vegetables
❌Berries, raisins, figs
❌Vegetable or fruit juices with pulp or seeds

Whole grain products:
❌Unpolished (brown) rice

❌With added malt (e.g Milo/Horlicks)

❌Crunchy peanut butter
❌Seeds, nuts (e.g watermelon seeds, sunflower seeds)

For the day before the endoscopy, your doctor may advise you to take a clear liquid diet. Avoid drinking red coloured fluids as this may be mistaken for blood during the colonoscopy.

Remember that you will have to pass out whatever that you eat. Some patients will take a very large meal before starting to take the bowel cleansing solution, thinking that it will be their last meal for a long time. Patients who do this may feel very uncomfortable whilst taking the bowel cleansing fluid and will often lead to a retained faecal material.

Remember that the low residue diet is temporary and just for a few days prior to the scope. Your adherence to this will make the bowel preparation with the cleansing fluid a more pleasant experience and will have less retained faecal material.

Timing of preparation 

The exact bowel preparation will be informed to you by your doctor/nurse. There are several effective regimes.

Bowel preparation is commonly prescribed in 2 parts (or split), with one portion the day before endoscopy and another portion on the day of colonoscopy. The second portion of the cleaning fluid should be taken 3 to 8 hours prior to the colonoscopy.

It is important to finish drinking your bowel cleansing fluid. Most of the regimes are fairly high volume (2 to 3L). Please ensure the liquid is well mixed before consuming.

As you are drinking the bowel preparation, you will go to the toilet to pass motion several times. The stool consistency should change from solid stool to a watery stool, and finally to a clear liquid. This experience is similar to having diarrhoea. After completing the bowel preparation, you should be passing clear to a clear/yellow fluid.

It is crucial to finish the fluid. Drinking 500mls to 1L of fluid will not be sufficient to cleanse your bowel adequately.

After drinking the fluid, you will need to fast for 3-4 hours prior to the colonoscopy. Do not eat any food during this time. If you are thirsty, small sips of water may be taken to quench thirst.

Stopping of medications 

Your doctor may advise you to stop certain blood-thinning medicines that may increase your bleeding if therapeutic procedures are performed during the colonoscopy. These include medications such as aspirin, clopidogrel or anticoagulants such as warfarin, rivaroxaban etc.

Please check with your doctor or counselling staff about which medications to continue. Typically, blood pressure medications should be taken the morning of the procedure as usual. Diabetic medications, for example, may need dose adjustments.

Bowel preparation is an essential part of preparing for a colonoscopy. Patients play a key role in a successful cleansing of their bowel to allow for a safe and thorough colonoscopy. Remember that dietary changes are temporary and that it is better to complete the bowel cleansing fluid, rather than to give up halfway, resulting in either postponement or a repeat procedure.