Pathophysiology of Malabsorption Digestion and absorption occur in three phases: Intraluminal hydrolysis of fats, proteins, and carbohydrates by enzymes—bile salts enhance the solubilization of fat in this phase Digestion by brush border enzymes and uptake of end-products Lymphatic transport of nutrients The term malabsorption is commonly used when any of these phases is impaired, but, strictly speaking, impairment of phase 1 is maldigestion rather than malabsorption.