| Summary: | Growing evidence suggests that
symptoms in patients with irritable bowel syndrome (IBS) may be
due to a visceral sensory dysfunction. Specifically, it has been
shown that patients with IBS have hypersensitive responses to distension
of the rectum, whereas their tolerance to somatic stimuli is
normal or even increased. Furthermore, patients with IBS have
hypersensitivity of the small bowel, which selectively affects
mechanosensitive afferents, with normal perception of electrical
stimulation of the gut. Sensory dysfunctions may also be associated
with altered reflex activity, which may contribute to the clinical
symptoms. Normally, a series of mechanisms at different strata
of the nervous system modulate visceral afferent input and determine
conscious perception. Conceivably, a dysfunction of these
regulatory mechanisms may alter sensitivity in clinical conditions.
To date, neither the origin nor the clinical significance of
visceral hyperalgesia has been elucidated. However, it seems likely
that the sensory and reflex dysfunctions of the gut in IBS may
combine to different degrees, and their interaction may explain
the clinical pleomorphism of the syndrome.
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