Physiology of malabsorption

Malabsorption occurs when the function of the gastrointestinal tract is suboptimal and nutrient absorption is reduced. Malnutrition, weight loss, diarrhoea, steatorrhoea, anaemia and other specific nutrient deficiencies can be produced. This article will review the principles of normal nutrient absorption and the pathophysiology in disorders which result in malabsorption. Normal absorption needs coordinated processes of motility, hormone release, digestive secretion from the salivary glands, stomach, pancreas, liver and intestine, and the expression of specific enzymes and transporter molecules. Gastric, pancreatic and intestinal disorders can all produce malabsorption. These can be complications of surgical procedures, or be due to inflammatory and autoimmune disorders such as coeliac disease, Crohn's disease, small intestinal bacterial overgrowth, chronic pancreatitis, or autoimmune gastritis. Understanding the mechanisms involved and how these are affected by surgical procedures and disease will enable malabsorption to be recognized, investigated and treated appropriately.