Bowel Preparation Before Colonoscopy

Introduction

A successful colonoscopy requires adequate preparation of the large bowel to facilitate clear visualization of the mucosal surface.

Timing of Bowel Preparation

The timing and dosing schedule of bowel preparation can be divided into 2 regimens.

Split-dose preparation

For morning colonoscopy, split-dose preparation refers to administration of half of the colon cleansing agent the evening prior to the colonoscopy and the second half the morning of the colonoscopy.
This regimen is associated with improved efficacy and patient tolerance.

Single dosing of the full preparation

This regimen is preferred by some patients for convenience reasons.

Dietary Preparation

Patients should consume a low-residue diet or clear liquids for at least one day prior to the elective procedure.

A low-residue diet is low in fiber, and patients should avoid foods such as fruits, vegetables and whole grains.
Clear liquids include water, clear broth, coffee or tea (without milk), ices, gelatins and fruits juices, such as apple, grapefruit and lemonade.

Based on product leaflets, if the patient is taking Fortrans, he can take either a low-fiber diet (e.g. plain porridge, white fish and skinless chicken) or clear liquids. However, if the patient is taking oral Fleet solution, he can only take clear liquids.

A 2009 trial found that there was no significant difference in preparation quality between patients treated with 4L of polyethylene glycol who were assigned to receive either a low-residue diet or clear liquids the day prior to the examination.

Other Key Considerations

Adequate hydration is essential for preventing dehydration.

Oral Fortrans (isosmotic laxative)

Usual dose: 3 litres of oral solution are required.
1 sachet dissolved in 1 litre of water and to be consumed within 1 hour.

Oral Fleet phosphosoda

Usual dose: 2 doses are required and timing of doses is dependent on the timing of procedure.
Dilute the contents of 45 ml bottle in half a glass (120 ml) of cold water. Drink this and follow it with at least one full glass (240 ml) of cold water.
8 glasses of water (1 glass = 240 ml) are the minimum requirement, however, patients should drink as much as possible.

Most medications may be continued immediately prior to colonoscopy. However, some medications may need to be adjusted prior to the colonoscopy, such as

Medications for diabetes due to decreased oral intake prior to the procedure.
Oral iron should be stopped at least 5 days before the colonoscopy since it makes the residual faeces black, viscous and difficult to purge.
Anticoagulant medication

Liquids that are red can be mistaken for blood in the colon or can obscure mucosal details and should therefore be avoided.

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