Table 2.

Mechanisms of malabsorption

Abnormality	Underlying pathology
Defective intraluminal digestion	Pancreatic dysfunction Pancreatic insufficiency (pancreatitis or cystic fibrosis) Inactivation of pancreatic enzymes by excess gastric acid secretion (Zollinger–Ellison syndrome) Deficient or ineffective bile salts Decreased bile salt uptake (ileal resection or dysfunction) Impaired excretion of bile – (liver disease) After rerouting surgery (gastrectomy and bypass) Disaccharidase deficiency (primary disaccharidase deficiency) or secondary (damage to villi due to celiac disease)
Mucosal or mural abnormalities	Gluten-sensitive enteropathy (celiac disease) Short gut syndrome Crohn's disease Allergic and eosinophilic gastroenteritis Neonatal enteropathies Abetalipoproteinemia Muscular or neurogenic defect of intestinal wall (amyloidosis and scleroderma) Intestinal lymphangiectasia
Infections	Bacterial overgrowth Whipple's disease Parasitic infestation Tropical sprue Giardiasis Cryptosporidiosis and isosporidiosis