The Pathophysiology of Irritable Bowel SyndromeCME - Medscape

www.medscape.org/lecture/ibs/pathophysiologySlide 7.What might be the cause of this underlying change in transit through the colon? Recent research suggests that excess hepaticsynthesis and excretion of bile acids may contribute to IBS-D; and that decreased production and excretion may contribute toIBS-C. [7]We know that certain types of bile acids have at least 2 α-hydroxy groups at the 3, 7, and 12 positions are natural secretory agents;they are natural laxatives that facilitate movement of contents through the colon. There is now evidence that a deficiency in thesesecretory bile acids contributes to the slow transit in patients who have constipation or IBS-C. This is relevant as it may provide arationale for new approaches to treatment of both diarrhea and constipation in IBS.Slide 8.A second major peripheral mechanism pertains to the sensing of the small bowel and colon, and responses to those sensations. [4]Activation of local secretory and motor reflexes and sensory mechanisms may result from ingestion of foods that stimulateenteroendocrine cells or the organic acids, such as short-chain fatty acids (SCFAs) that are produced by the breakdown of complexcarbohydrates in the colon by the resident microflora. As mentioned earlier, it may also be related to the presence of bile acidsthat bypass the ileal reabsorptive mechanism and reach the colon, causing symptoms such as diarrhea, bloating, andabdominal pain.Pg.9