Irritable Bowel Syndrome (IBS) is the most common type of functional gastrointestinal disorder, characterized primarily by abdominal pain accompanied by changes in habitual bowel patterns. The abdominal pain is related to defecation, often improving after bowel movements, and the symptoms frequently recur or are chronically persistent. Thus, IBS is a functional disease, meaning it does not involve organic changes. In other words, medical examinations do not reveal problems in any specific part of the body. Therefore, IBS cannot be detected with a CT scan, and CT also cannot visualize the intestinal mucosa. Even diseases like chronic colitis cannot be detected with a CT scan. Any diseases involving the gastrointestinal mucosa cannot be uncovered by CT, hence diagnosis requires the use of gastroscopy or colonoscopy.