Irritable bowel syndrome
Irritable bowel syndrome (IBS) is a fairly common problem with the way the large intestine works. The large intestine (also known as the colon) absorbs water and nutrients from the partially digested food that enters the colon from the small intestine. Anything that is not absorbed is slowly moved on a pathway out of your body. These undigested and unabsorbed food particles are also known as stool or a bowel movement.
Here's why an intestine gets "irritable." To have a bowel movement, the muscles in the colon and the rest of the body have to work together. If this process is somehow interrupted, the contents of the colon can't move along very smoothly. It sort of stops and starts, doesn't move, or sometimes moves too fast. This can hurt and make you feel awful. Doctors also believe that people with IBS may have more sensitive bowels, so what might cause a little discomfort in one person causes serious pain for someone with IBS.
Between 5% to 20% of kids have IBS, and about one in five adults do, too