Clinical Information

Malabsorption is defined as impaired gastrointestinal (GI) absorption of nutrients, including fats, proteins, carbohydrates, vitamins, and minerals. The classic presentation of malabsorption is chronic diarrhea; however, many patients may not display this symptomatology. Instead, they may present with mild GI symptoms and weight loss or with systemic manifestations associated with a specific nutrient deficiency.

Malabsorption can result from different pathologic mechanisms; identification of the specific cause is important for proper treatment. Evaluation for the cause of malabsorption requires a variety of blood and stool tests. Stool testing as a more direct marker of GI function is particularly useful for certain diseases. Fecal calprotectin concentrations are a reflection of the number of neutrophils in the GI tract, with an elevated result consistent with an inflammatory condition such as inflammatory bowel disease. Elastase is an enzyme produced by the pancreas and decreased concentrations in the stool are indicative of pancreatic insufficiency and malabsorption due to a deficiency in digestive enzymes.

The reducing substances test is useful in cases of chronic diarrhea; increased concentrations are consistent with osmotic diarrhea caused by disaccharidase deficiency or intestinal monosaccharide malabsorption. In comparison, measurement of alpha-1-antitrypsin in stool is not diagnostic for a specific malabsorption etiology but is useful for determining the extension of protein loss through the GI tract.