This is a syndrome of numerous diverse origins resulting in failure to absorb dietary nutrients. The term is usually used to describe a global failure of absorption, and is not usually applied to a failure to absorb specific substances, e.g. vitamin B12.
Common causes are gluten enteropathy, Crohn’s disease of the small intestine, bacterial overgrowth and gastric or small-bowel surgery.
Less commonly, pancreatic, hepatic or biliary disease, or chronic Giardia intestinalis (formerly G. lamblia) or other infections, may be responsible.
However, any condition causing chronic diarrhea may lead to malabsorption.
Malabsorption may also be drug-induced. The lipid-regulating drugs cholestyramine and colestipol bind bile salts and so may cause a failure to absorb dietary lipids. If these anion exchange resins are continued long term there may be an associated failure to absorb fat-soluble vitamins, so supplements of vitamin A, D and K may be required.
Orlistat also reduces lipid absorption, with similar potential consequences. Some broad-spectrum antibiotics, notably those that cause antibiotic associated colitis (e.g. pseudomembranous colitis), may also cause metabolic disturbances.
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