Before some tests, you will have to empty your bowel completely to make sure the doctor can see the bowel clearly. This is called bowel preparation (or washout). The bowel preparation process can vary, so ask your doctor what you need to do. It’s important to follow the instructions you are given so you don’t have to repeat the test.
Here are some ways you may be asked by your doctor to prepare your bowels before a diagnostic test:
 | Change dietA few days before the test, start eating low-fibre foods, such as white bread, white rice, meat, fish, chicken, cheese, yoghurt, pumpkin and potato. Don’t eat high-fibre foods, such as most vegetables, fruit, wholegrain pasta, brown rice, cereals, nuts and seeds. |
 | Take prescribed laxativesYou will be prescribed a strong laxative as a powder you need to mix with water, or as a tablet. You will take the laxative over several hours, starting 12–18 hours before the test. The laxative will cause you to have several episodes of watery diarrhoea and you will need to stay home to be near a toilet. |
 | Drink clear fluidsYour doctor might advise you to have nothing but clear fluids (e.g broth, water, black tea and coffee, clear fruit juice without pulp) for 12–24 hours before the test. This will help to prevent dehydration. |
Have an enema, if required
One common way to clear the lower part of the bowel is using an enema. You may be given an enema by a nurse at the hospital before a colonoscopy if the laxative hasn’t completely cleaned out the bowel, or if you are only having a flexible sigmoidoscopy. An enema involves putting liquid directly into the rectum. The liquid washes out the lower part of the bowel, along with any faeces.
→ READ MORE: Staging and prognosis for bowel cancer
More resources
A/Prof David A Clark, Senior Colorectal Surgeon, Royal Brisbane and Women’s Hospital, QLD, The University of Queensland and The University of Sydney; Yvette Adams, Consumer; Dr Cameron Bell, Gastroenterologist, Royal North Shore Hospital, NSW; Katie Benton, Advanced Dietitian Cancer Care, Sunshine Coast University Hospital and Queensland Health, QLD; John Clements, Consumer; Dr Fiona Day, Medical Oncologist, Calvary Mater Newcastle, NSW; Alana Fitzgibbon, Clinical Nurse Consultant, GastroIntestinal Cancers, Cancer Services, Royal Hobart Hospital, TAS; Prof Alexander Heriot, Consultant Colorectal Surgeon, Director Cancer Surgery, Peter MacCallum Cancer Centre, and Director, Lower GI Tumour Stream, Victorian Comprehensive Cancer Centre, VIC; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Dr Kirsten van Gysen, Radiation Oncologist, Nepean Cancer Care Centre, NSW.
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