Significance of visceral hypersensitivity in IBS
- IBS patients have lower pain thresholds to balloon-distention volumes specific to the GI tract (i.e., rectosigmoid, descending colon, small intestine, stomach, and esophagus) in comparison with healthy individuals.
- The cause of visceral hypersensitivity in IBS is not completely understood. However, researchers now believe that noxious stimuli can change the synaptic efficiency of peripheral and central neurons.
- This may occur through altered release of serotonin (5-HT) from the enteroenteric cells in the myenteric plexus or release of inflammatory cytokines from activated immune or inflammatory cells in response to infection or injury.
- Through a process known as the wind-up, neurons can develop a pain memory that can persist long after the noxious stimulus is removed. IBS patients may also be prone to developing sensitization.
- Repetitive sigmoid contractions, such as those that may occur during intense stress, could induce sensitization in a person predisposed to developing IBS, thereby causing rectosigmoid hypersensitivity.
- Although 95% of IBS patients have rectal sensory abnormalities, rectal sensitivity testing is not currently widely used in the diagnosis or management of IBS, partly because of the lack of standardization in balloon-distention protocols, the limited correlation between symptom severity or response to therapy, and the significant overlap with other GI diseases.
- Therefore, its clinical utility in making a definitive diagnosis of IBS is limited.