Specific Absorptive Defects

Primary lactase deficiency is an example of a defect in a specific brush border enzyme, lactase, which causes the malabsorption of the disaccharide lactose.

Bile Acid Insufficiency

The treatment of bile acid insufficiency varies with the cause. Improvement in the liver disease or relief of the biliary obstruction may be adequate.


The term malabsorption connotes the failure to absorb or digest normally one or more dietary constituents. Patients with malabsorption often complain of diarrhea, and sometimes the distinction between malabsorption and diarrhea of other causes initially is difficult. For example, patients with primary lactase deficiency fail to absorb a specific dietary constituent, lactose, and a watery, osmotic diarrhea develops.

Small-bowel Disease

When small-bowel mucosal disease is suspected, the question often is when to perform the small-bowel biopsy. Some physicians proceed directly to biopsy in the clinical setting of apparent panmalabsorption and an abnormal small-bowel x-ray series without clinical suspicion of pancreatic disease. Others first order a xylose tolerance test to confirm mucosal disease and obtain a 72-hour stool fat collection to quantitate the steatorrhea.