What are the causes and treatments of malabsorption related to gastrointestinal issues?

Malabsorption: Causes and Treatment

The most common causes of gastrointestinal malabsorption are celiac disease, lactose intolerance, bile acid malabsorption, exocrine pancreatic insufficiency, and small intestinal bacterial overgrowth (SIBO), each requiring specific diagnostic approaches and targeted therapies. 1

Clinical Presentation

Malabsorption presents with both classic gastrointestinal and extraintestinal manifestations that clinicians must recognize:

Gastrointestinal symptoms:

• Diarrhea, steatorrhea (fatty stools), weight loss, flatulence, and postprandial abdominal pain 2

Extraintestinal manifestations:

• Elevated liver enzymes, anemia, dermatologic conditions, infertility, and bone disease (osteoporosis) 3, 2
• Many patients present with subtle findings without obvious GI symptoms, requiring high clinical suspicion 3

Diagnostic Approach

Initial workup should include screening for anemia and stool studies to confirm fat malabsorption. 2, 4

The algorithmic evaluation proceeds as follows:

1. If fat malabsorption is confirmed: Perform endoscopy with small-bowel biopsies and aspirates for bacterial culture 4

2. If endoscopy is normal: Assess pancreatic function 4

3. If pancreatic function is normal and bile acid deficiency is absent: Obtain small bowel imaging to identify anatomical abnormalities 4

Critical caveat: Patients should NOT restrict their diets before testing for malabsorption syndromes, as this can lead to false-negative results. 2

Specific Causes and Treatments

Celiac Disease

Celiac disease is the most common malabsorption syndrome, triggered by gluten exposure. 1

Diagnosis:

• Tissue transglutaminase immunoglobulin A (tTG-IgA) is the diagnostic test of choice 1
• Duodenal biopsy remains the gold standard for confirmation 4
• Serological markers have high sensitivity and specificity 4

Treatment:

• Strict gluten-free diet is the primary and definitive intervention 1, 2
• Diagnosis is confirmed by clinical and endoscopic response to gluten avoidance 4
• Suspect intestinal lymphoma in patients unresponsive to gluten-free diet 4

Lactose Intolerance

Lactose intolerance results from absent or declining lactase enzyme levels. 1

Diagnosis:

• Primarily clinical diagnosis 1
• Hydrogen breath test can confirm if diagnosis is uncertain 1, 2

Treatment:

• Lactose-restricted diet and dairy substitutes 2

Bile Acid Malabsorption

Unabsorbed bile acids in the colon cause secretory diarrhea. 1

Diagnosis:

• 75selenium homotaurocholic acid test is most accurate but not widely available 1
• Therefore, an empiric trial of bile acid sequestrants is a reasonable diagnostic and therapeutic approach when suspected 1

Treatment:

• Cholestyramine (bile acid sequestrant) is the typical first-line therapy 1

Exocrine Pancreatic Insufficiency

This occurs from decreased pancreatic enzyme production, typically in patients with preexisting pancreatic damage from alcohol, surgery, radiation, diabetes, or cystic fibrosis. 1

Diagnosis:

• Fecal fat testing or fecal elastase-1 tests 1

Treatment:

• Pancreatic enzyme replacement therapy 1, 2
• Replacement of fat-soluble vitamins (A, D, E, K) 2

Small Intestinal Bacterial Overgrowth (SIBO)

SIBO results from pathologic overgrowth of the small bowel microbiome. 1

Diagnosis:

• Jejunal biopsy (gold standard) or breath tests (more commonly used) 1, 5

Treatment:

• Rifaximin is the typical first-line antibiotic 1
• Alternative options include dietary modifications, probiotics, and prokinetic drugs 1

Additional Considerations

If initial evaluation for celiac disease is negative, consider:

• Nonceliac gluten sensitivity 2
• Irritable bowel syndrome 2
• FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) intolerance 2

Malabsorption can also result from diseases of the pancreas, liver, biliary tract, and stomach—not just small intestinal pathology. 3 The pathophysiology involves either maldigestion (defective intraluminal hydrolysis) or malabsorption (defective mucosal absorption). 3