Bleeding, fever, weight loss, and persistent severe pain are not symptoms of IBS, and may indicate other problems. IBS usually is diagnosed after doctors exclude more serious organic diseases. The doctor will take a complete medical history that includes a careful description of symptoms. A physical examination and laboratory test will be done. A stool sample will be tested for evidence of bleeding.
Many people report that their symptoms occur following a meal or when they are under stress.
No one is sure why this happens, but scientists have some clues. Eating causes contractions of the colon. Normally, this response may cause an urge to have a bowel movement within 30 to 60 minutes after a meal. In people with IBS, the urge may come sooner and may be associated with pain, cramps and diarrhea. The strength of the response is often related to the number of calories in a meal, and especially the amount of fat in a meal.