In order for the colon to be viewed unobstructed by stool, patients prepare in advance for the colonoscopy. This bowel prep procedure is the part of the process that often makes people uneasy. The preferred method varies widely from physician to physician but the idea is the same; clean the colon clear so that no polyp or cancer is missed. An inadequately cleansed colon can jeopardize the effectiveness of the test.
The best way to clear the colon is to forgo solid food entirely (liquids only) and induce diarrhea to expel what solids are left inside the colon. There are a few methods for bowel cleansing; drinking a copious amount of a salty solution, or pills and water - both cause high-volume diarrhea in a few hours. Your doctor will give you specific instructions so read them carefully a few days in advance. Expect to spend the day near the toilet.