Clinical meaning
Malabsorption syndromes encompass a diverse group of disorders characterized by impaired absorption of nutrients, vitamins, minerals, and fluids from the gastrointestinal tract. To understand malabsorption, it is essential to understand normal absorption. The small intestine is the primary site of nutrient absorption, with a total surface area of approximately 200 square meters due to the presence of circular folds (plicae circulares), villi, and microvilli that form the brush border. The duodenum absorbs iron, calcium, and folate. The jejunum is the primary site for absorption of carbohydrates, proteins, fats, fat-soluble vitamins (A, D, E, K), and water-soluble vitamins. The ileum absorbs vitamin B12 (bound to intrinsic factor), bile salts, and remaining nutrients. Malabsorption occurs when any component of the digestive and absorptive process is disrupted. Celiac disease (celiac sprue, gluten-sensitive enteropathy) is an autoimmune disorder triggered by ingestion of gluten, a protein found in wheat, barley, and rye. In genetically susceptible individuals (carrying HLA-DQ2 or HLA-DQ8 genes), gluten triggers an immune response that damages the intestinal mucosa, causing villous atrophy, crypt hyperplasia, and intraepithelial lymphocyte infiltration. The resulting loss of absorptive...