Mechanisms and Features
Malabsorption can result from problems with digestion (for example, inadequate pancreatic enzymes or bile), damage to the absorptive mucosa, or reduced absorptive surface. The classic clinical picture is steatorrhea — bulky, greasy, foul-smelling stools that float — along with weight loss despite adequate intake. Deficiencies produce specific findings: the fat-soluble vitamins (A, D, E, K), iron and B12 anemias, and calcium-related bone disease.
Major Causes
Common causes span the digestive process. Celiac disease damages the small intestinal villi through an immune reaction to gluten. Chronic pancreatitis and cystic fibrosis cause pancreatic exocrine insufficiency with inadequate enzymes. Crohn disease and intestinal resection reduce absorptive surface. Other causes include bacterial overgrowth, lactose intolerance (a specific carbohydrate malabsorption), and Whipple disease.
Diagnosis
The workup first confirms malabsorption and then finds the cause. Fecal fat testing (or the qualitative Sudan stain) demonstrates fat malabsorption. Targeted tests follow the suspected cause: celiac serology (anti-tissue transglutaminase) and duodenal biopsy for celiac disease, pancreatic function or imaging for pancreatic insufficiency, and tests for bacterial overgrowth. Blood work reveals the pattern of nutritional deficiencies.
Management
Treatment addresses the underlying cause and corrects deficiencies. A gluten-free diet treats celiac disease, pancreatic enzyme replacement treats exocrine insufficiency, and antibiotics treat bacterial overgrowth. Alongside cause-specific therapy, patients receive supplementation of the deficient nutrients — including fat-soluble vitamins, iron, B12, and calcium — and nutritional support as needed.