Lecture on Malabsorption and Maldigestion

Introduction

• Focus on malabsorption as part of clinical medicine.
• Emphasis on understanding and differentiating malabsorption from maldigestion.
• Encouragement to visit the website for more resources like notes, illustrations, and quizzes.

Definitions and Differences

Malabsorption

• Occurs when the mucosa is injured.
• Enzymes are normal, but nutrients such as carbohydrates, fats, and proteins cannot be absorbed due to damaged enterocytes.
• Results in nutrient loss: fats, proteins, carbohydrates, and micronutrients.
• Mucosal injury leads to mucosal dysfunction.

Maldigestion

• Intact mucosa but issues with digestive enzymes.
• Enzyme dysfunction or deficiency prevents the breakdown of macronutrients into absorbable molecules.
• Large molecules remain, leading to decreased absorption.
• Selective nutrient loss depending on which enzyme is deficient.

Causes

Causes of Malabsorption

• Celiac Disease: Gluten sensitivity causing mucosal damage via an immune response.

  • Triggered by gliadin (a component of gluten).
  • Production of antibodies that cause mucosal injury.
  • Diagnostic antibodies: tissue transglutaminase (IgA), deaminated gliadin peptide (IgA), and endomysial antibodies (IgA).

• Whipple’s Disease: Caused by Tropheryma whipplei bacteria leading to mucosal injury.

• Tropical Sprue: Often occurs in tropical regions due to bacterial overgrowth (E. coli, Klebsiella).

Causes of Maldigestion

• Pancreatic Insufficiency: Reduced enzyme production due to diseases like chronic pancreatitis or cystic fibrosis.

• Bile Acid Deficiency: Issues with bile production, obstruction, or ileal disease (e.g., Crohn's disease) affecting fat digestion.

• Lactase Deficiency (Lactose Intolerance): Decrease or dysfunction in lactase enzyme, often acquired post-gastroenteritis.

Symptoms and Complications

Protein Malabsorption

• Muscle wasting and weight loss.

Carbohydrate Malabsorption

• Diarrhea due to osmotic activity of unabsorbed carbohydrates.
• Abdominal distension and pain, flatulence.

Fat Malabsorption

• Steatorrhea: greasy, foul-smelling stools.
• Fat-soluble vitamin deficiencies (A, D, E, K):
  • Vitamin A: night blindness.
  • Vitamin D: rickets or osteomalacia.
  • Vitamin E: neuropathy, hemolytic anemia.
  • Vitamin K: bleeding disorders.

Micronutrient Malabsorption

• Anemia due to deficiencies in B12, folate, and iron.

Diagnostic Approach

• D-xylose Test: Differentiates between malabsorption (low absorption) and maldigestion (normal absorption).
• Fecal Fat Test: Indicates malabsorption.
• Hydrogen Breath Test: For lactose intolerance.
• Serological Tests: Antibodies for celiac disease.
• Biopsy: Confirms diagnoses like Whipple’s or celiac disease.

Treatment

Malabsorption

• Celiac Disease: Gluten-free diet.
• Whipple’s Disease: Antibiotics (Ceftriaxone, followed by TMP-SMX).
• Tropical Sprue: Antibiotics (Tetracycline).
• Nutrient Replacement: Supplement deficiencies.

Maldigestion

• Pancreatic Insufficiency: Pancreatic enzyme replacement.
• Lactose Intolerance: Avoid lactose or take lactase supplements.

Conclusion

• Recap of Global vs Partial Malabsorption.
• Importance of differentiating between mucosal and enzyme-related issues.
• Encouragement to understand and apply the concepts in clinical settings.