Physiological stimuli in the gut induce regulatory reflexes to accomplish the digestive process, but are normally not perceived. However, under some circumstances, gut stimuli may activate perception pathways and induce conscious sensations. Experimental evidence gathered during the past decade suggests that patients with functional gut disorders and unexplained abdominal symptoms may have a sensory dysfunction of the gut, so that physiological stimuli would induce their symptoms. Assessment of visceral sensitivity is still poorly developed, but in analogy to somatosensory testing, differential stimulation of visceral afferents may be achieved by a combination of stimulation techniques, which may help to characterize sensory dysfunctions. Visceral afferent input is modulated by a series of mechanisms at different levels of the brain-gut axis, and conceivably, a dysfunction of these regulatory mechanisms could cause hypersensitivity. Alteration of visceral perception may result in unexplained symptoms characteristic of functional disorders. Furthermore, these patients also have altered visceral reflexes, and these mixed sensory-reflex dysfunctions may interact to produce the clinical syndrome. Evidence of a gut sensory-reflex dysfunction as a common pathophysiological mechanism in different functional gastrointestinal disorders would suggest that they are different forms of the same process, and that the clinical manifestations depend on the specific pathways affected. This unifying working hypothesis may be also extrapolated to explain the pathophysiology of other extradigestive functional syndromes.
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