While preparations for VC vary, the patient will usually be asked to take laxatives or other oral agents at home the day before the procedure to clear stool from the colon. A suppository is also used to cleanse the rectum of any remaining fecal matter. The patient may also be given a solution designed to coat any residual faeces which may not have been cleared by the laxative, called 'faecal tagging'. This allows the physician (usually a consultant radiologist), viewing the 3D images to effectively subtract the left-over faeces, which may otherwise give false positive results.