Before some tests, you will have to clean out your bowel completely to make sure the doctor can see the bowel clearly. This is called bowel preparation (or washout). The process can vary, so ask your doctor what you need to do. It’s important to follow the instructions 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. Avoid high-fibre foods, such as vegetables, fruit, wholegrain pasta, brown rice, cereals, nuts and seeds. |
 | 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. |
 | Take prescribed laxativesYou will be prescribed a strong laxative to take 12–18 hours before the test. This is taken by mouth as a tablet or liquid over several hours. It will cause you to have several episodes of watery diarrhoea. |
Have an enema, if required
One common way to clear 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.
More resources
A/Prof David A Clark, Colorectal Surgeon, Royal Brisbane and Women’s Hospital, and The University of Queensland, QLD, and The University of Sydney, NSW; A/Prof Siddhartha Baxi, Radiation Oncologist and Medical Director, GenesisCare Gold Coast, QLD; Dr Hooi Ee, Specialist Gastroenterologist and Head, Department of Gastroenterology, Sir Charles Gairdner Hospital, WA; Annie Harvey, Consumer; A/Prof Louise Nott, Medical Oncologist, Icon Cancer Centre, Hobart, TAS; Caley Schnaid, Accredited Practising Dietitian, GenesisCare, St Leonards and Frenchs Forest, NSW; Chris Sibthorpe, 13 11 20 Consultant, Cancer Council Queensland; Dr Alina Stoita, Gastroenterologist and Hepatologist, St Vincent’s Hospital Sydney, NSW; Catherine Trevaskis, Gastrointestinal Cancer Specialist Nurse, Canberra Hospital, ACT; Richard Vallance, Consumer.
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