Irritable bowel syndrome (IBS) affects the gastrointestinal (GI) tract, especially the colon (the large bowel). Irritable bowel syndrome causes diarrhea and sometimes constipation (difficulty with bowel movements). Approximately 20% of persons in the developed world have IBS symptoms at some time in their lives. Irritable bowel syndrome is generally diagnosed when more serious problems like inflammatory bowel disease (Crohn disease and ulcerative colitis), celiac disease, infection with parasites, cancer, or malabsorption (bowel does not absorb nutrients properly) have been looked for and not found. Women are more likelythan men to have IBS. People who have continuous or recurring diarrhea, constipation, or both are often referred to a gastroenterologist, a doctor with specialized education in the management of digestive diseases, including bowel problems. Irritable bowel syndrome is called a functional disorder because there is no known physical cause for its signs and symptoms. It is important to seek medical attention if you have episodes of diarrhea or constipation on a regular basis, have a change in your bowel habits, or experience bloody stools because these may be signs of serious medical issues, such as colon or rectal cancer or inflammatory bowel disease.