Clinical Features of Malabsorptive Disorders, Small-Bowel Diseases, and Bacterial Overgrowth Syndromes Amy S. Oxentenko, MD

MALABSORPTIVE DISORDERS AND DIARRHEA Malabsorption (defect in the mucosal absorption of nutrients) and maldigestion (defect in the hydrolysis of nutrients) both imply disordered physiologic mechanisms in the gastrointestinal system. Malabsorption and maldigestion of nutritional substrates can occur in multiple phases: 1) the luminal phase, in which there is contact with various digestive enzymes, 2) the mucosal phase, in which substances are assimilated and absorbed in the required constituent form, and 3) the delivery phase, in which nutrients are taken up into the cytoplasm and transported to the lymphatics or portal venous system (Table 1).