![]() ![]() Small Intestinal Bacterial Overgrowth (SIBO) is essentially the presence of excessive bacteria in the small intestine. Small Intestinal Bacterial Overgrowth (SIBO) Pathophysiology. "Small Intestinal Bacterial Overgrowth (SIBO) Pathophysiology". Please use one of the following formats to cite this article in your essay, paper or report: What Causes Small Intestinal Bacterial Overgrowth (SIBO)?.Fibromyalgia and Small Intestinal Bacterial Overgrowth (SIBO).Other toxic compounds induce mucosal inflammation and worsen small intestinal mucosal permeability.įinally, SIBO is more toxic in patients programmed to produce less IL-1 receptor antagonist genes, but higher proinflammatory cytokines, such as IL-6 or tumor necrosis factor-alpha. This dysmotility is exacerbated by metabolites of Gram-negative bacteria, lipopolysaccharides, endotoxins and ethanol, besides certain neurotransmitters.Īmmonia overproduction occurs as the intraluminal proteins are also digested. These fatty acids inhibit proper absorption it slows down jejunal movements via the secretion of peptide YY, and other peptides. The presence of excessive lactulose and other simple sugars as substrates for fermentation, produce short-chain fatty acids that are crucial for colonic health, but toxic to the small bowel. This reduces the absorption of lactulose, sucrose and sorbitol in the small intestine. Patients with SIBO often have a relative deficiency of disaccharidases as the brush border is damaged. Malabsorption due to mucosal inflammation also causes more fermentable carbohydrates to pass down into the large bowel with a rise in gas production. This leads to vitamin deficiencies including neuropathy due to low levels of cobalamin. Lack of micellar formation causes fat malabsorption, accompanied by the resulting lack of fat-soluble nutrients such as vitamins A, D and E. This leads to the formation of free bile acids, which further damage the intestinal lumen and also reduce micelle formation, being absorbed in the jejunum rather than the ileum. Bile Acid Deconjugationīacterial deconjugation of bile acids is another important feature in SIBO. Inflammation of the mucosa of the small bowel leads to loss of the brush border, which in turn reduces the absorptive area in the small intestine. Of these, the most important are mucosal inflammation. The severity and frequency of the symptoms in SIBO are linked to the presence of large numbers of bacteria as well as related complications. This in turn causes the typical symptoms such as bloating, flatulence, abdominal cramps and altered bowel movements. Once colonic bacteria overgrow in the proximal small bowel, fermentable carbohydrates are acted upon by proliferating coliforms or oral bacteria to form excessive gas in the intestine. The intact ileocecal valve that acts as a barrier by its mechanical and physiological actions.Presence of commensals such as lactobacilli.Powerful digestive actions of pancreatic, intestinal and biliary juices.Mucus layer coating the mucosal cells and preventing bacterial binding.Other ways in which the normal small intestine acts to prevent bacterial growth is: By physically moving bacteria onward with the food stream, it makes it impossible for most of them to colonize this part of the gut. The second powerful force is the propulsive force of the smooth muscle in the small intestine wall, especially the migrating motor complexes, which shift food downward in a series of contractions. This is despite the fact that significant amounts of bacteria enter with each swallow from the oropharynx. Under normal health conditions, the high acidity of the stomach ensures a more or less zero bacterial count in the stomach, and prevents significant bacterial growth in the upper small intestine, all the way until the terminal ileum. This in turn leads to atrophy of the intestinal villi, with infiltration by lymphocytes. Once bacteria from the colon grow into the small intestine and colonize it, this may result in mucosal inflammation usually on a microscopic scale. However, some other risk factors are known, including anatomic abnormalities of the small or large intestine, and disrupted gut immune function. The most common ways in which this happens seems to be hypchlorhydria and dysmotility of the small bowel. The occurrence of SIBO shows that normal regulatory mechanisms that keep bacterial populations in the small and large intestines have been disturbed in some way. Image Credit: CHAjAMP / Shutterstock Normal Barriers to SIBO ![]()
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