Malabsorption: Conditions causing malabsorption, categorized by the phase of absorption that is impaired

Phase and nature of malabsorptive defect	Example
Luminal phase
A. Substrate hydrolysis
1. Digestive enzyme deficiency	Chronic pancreatitis
2. Digestive enzyme inactivation	Zollinger-Ellison syndrome
3. Dyssynchrony of enzyme release, inadequate mixing	Post Billroth II procedure
B. Fat solubilization
1. Diminished bile salt synthesis	Cirrhosis
2. Impaired bile secretion	Chronic cholestasis
3. Bile salt de-conjugation	Bacterial overgrowth
4. Increased bile salt loss	Ileal disease or resection
C. Luminal availability of specific nutrients
1. Diminished gastric acid	Atrophic gastritis - vitamin B12
2. Diminished intrinsic factor	Pernicious anemia - vitamin B12
3. Bacterial consumption of nutrients	Bacterial overgrowth - vitamin B12
Mucosal (absorptive) phase
A. Brush border hydrolysis*
1. Congenital disaccharidase defect	Sucrase-isomaltase deficiency
2. Acquired disaccharidase defect	Lactase deficiency
B. Epithelial transport
1. Nutrient-specific defects in transport	Hartnup's disease
2. Global defects in transport	Celiac sprue
Postabsorptive, processing phase
A. Enterocyte processing	Abetalipoproteinemia
B. Lymphatic	Intestinal lymphangiectasia

* This process is sometimes considered as part of the luminal phase.

Graphic 54743 Version 5.0