Examines visceral hypersensitivity in three groups of irritable bowel syndrome (IBS) patients. It is suggested that visceral hypersensitivity, as demonstrated by a lower pain threshold to distension of the colon in IBS patients, could explain a major part of the clinical symptomatology of these patients. A total of 46 IBS patients (either diarrhea predominant, constipation predominant, or alternating diarrhea and constipation predominant) and 14 healthy controls participated in the study that compared sensation and motility responses to graded distensions of the sigmoid colon. Results supported findings from a previous study that show reduced volume thresholds of IBS patients with abdominal pain symptoms and diarrhea, but not in constipated patients and controls. This lowered colonic compliance is sufficient enough to explain visceral hypersensitivity as well as the correlated increases in elicited contractions in IBS patients. The increased pressure thresholds that were found demonstrated that these patients do not suffer from genuine hyperalgesia; rather, they experience an abnormal tonic reflex response that produces steeper pressure volume curves. Thresholds for non-nociceptive sensations exhibited the same pattern. Finally, no differences were found between groups in somatic pain sensitivity. It is concluded that reliable visceral pain tests are important for the differentiation of the IBS subgroups as well as for other syndromes with gastrointestinal pain
