The initial presentation of irritable bowel syndrome (IBS) occurs between the ages of 30 and 50 in over one-half of patients diagnosed with the condition. The classic symptoms reported include abdominal pain, constipation, and/or diarrhea. Patients typically suffer from either diarrhea or constipation for the first few weeks to months. In some patients it may develop into alternating episodes of diarrhea and constipation. The symptoms are intermittent and often improve with age.
IBS patients are typically divided into subgroups of constipation-predominant, diarrhea-predominant, or alternating diarrhea-constipation symptoms occurring with similar frequency. Although these subdivisions are used to classify the disorder, the categories of patients are not exclusive.
The definitions of constipation and diarrhea are imprecise with considerable interpatient variability. In clinical trials, constipation is commonly defined as less than three bowel movements per week. Patients report difficult, painful evacuation and hard, pellet-like stools. Diarrhea is commonly characterized by the presence of three or more bowel movements per day more than 25% of the time or a daily stool output exceeding 200 grams. Patients with diarrhea-predominant symptoms report frequent bowel movements, loose or watery stools, and a sense of urgency before bowel movements.
The average patient experiences IBS symptoms approximately five to seven days each month. Severity varies by individual and is commonly classified as mild, moderate, or severe. Those patients categorized with mild irritable bowel syndrome (IBS) have symptoms that occur infrequently and occasionally interfere with normal daily functioning. Patients categorized with moderate IBS have symptoms that occur more intensely, and frequently interfere with daily activities, whereas those categorized with severe IBS demonstrate symptoms that are frequent, intense, and chronically interfere with daily functioning. Pain is most commonly located in the left lower quadrant of the abdomen and is described as non-localized, sharp, or achy. The painful symptoms of irritable bowel syndrome (IBS) generally improve upon defecation and in the evening hours. When surveyed, almost 40% of women with IBS described the experience of abdominal pain as “intolerable.” Interestingly, physicians who treat patients with IBS usually subjectively rate the pain of the individual significantly lower than patients score their own pain.
Patients with irritable bowel syndrome (IBS) may also experience other gastrointestinal symptoms such as bloating, flatulence, belching, nausea, and vomiting. Non-GI symptoms, including fatigue, sleep disturbances, migraines, and urinary problems, are also common. Exacerbation of symptoms often occurs during periods of stress or anger.