Malabsorptions

Malabsorption is a group of disorders characterized by impaired absorption of nutrients from the small intestine. It refers to defective digestion, absorption, or transport of macronutrients and micronutrients. Fat malabsorption is common and often leads to steatorrhea and deficiencies of fat-soluble vitamins.

Causes include mucosal diseases such as celiac disease and Crohn’s disease; pancreatic insufficiency from chronic pancreatitis or cystic fibrosis; bile acid malabsorption; small intestinal bacterial overgrowth; infectious enteropathies; surgical loss of bowel length (short bowel syndrome); and certain medications such as orlistat.

Pathophysiology commonly involves mucosal damage with reduced absorptive surface, pancreatic enzyme deficiency, or deficiency of bile acids that emulsify fats. Rapid intestinal transit and alterations in intestinal flora can worsen absorption.

Clinical features vary but usually include chronic diarrhea, bulky foul-smelling stools, bloating, gas, and weight loss. Signs of nutrient deficiencies may appear, such as iron- or folate-deficiency anemia, edema from protein loss or low albumin, bone pain from vitamin D deficiency, and easy bruising from vitamin K deficiency.

Diagnosis relies on clinical suspicion supported by tests. Fecal fat quantification or quantitative stool fat tests assess fat malabsorption; serum tests may show nutritional deficiencies. Other investigations include fecal elastase for pancreatic insufficiency, serology and duodenal biopsy for celiac disease, and imaging or endoscopy to evaluate structural disease.

Treatment targets the underlying cause and the nutrition problem. This may involve dietary modification, pancreatic enzyme replacement therapy, medium-chain triglyceride supplementation, and fat-soluble vitamin repletion. Prognosis depends on the etiology and response to therapy.