Sensory dysfunction and the irritable bowel syndrome

Dysfunction of the sensory system of the gut is now generally believed to be important in the pathophysiology of irritable bowel syndrome (IBS). This disturbance may well account for some of the symptoms of the disorder, such as abdominal pain, by virtue of the fact that intra-lumenal events (e.g. contractions) may be 'sensed' more easily. It can be assessed in the laboratory by a variety of techniques, but usually involves measuring the patient's response to distension of any site of the gut, most commonly the rectum. Hypersensitivity is the most frequent finding, but hyposensitivity can also occur--hypersensitivity does not appear to be specific to any particular pattern of bowel habit, but hyposensitivity does tend to be generally only seen in patients with constipation, especially those with the 'no urge' type. Although there is some evidence to support hypersensitivity being related to enhanced vigilance in some patients, other data suggest that there may be a true alteration in sensory processing. The mechanisms underlying this sensory dysfunction remain to be elucidated, but could involve changes in either the enteric, spinal and/or central nervous systems. Finally, factors such as gender, stress, emotion and infection can all influence the sensitivity of the gut and may therefore play a role in IBS.