What are malabsorption syndromes?

Malabsorption Syndromes

Malabsorption syndromes are conditions characterized by impaired digestion or absorption of nutrients, leading to nutritional deficiencies, gastrointestinal symptoms, and extraintestinal manifestations. 1

Types of Malabsorption Syndromes

• Pancreatic Exocrine Insufficiency (PEI): Results from inadequate pancreatic enzyme secretion causing impaired digestion of fats, proteins, and carbohydrates. Common in chronic pancreatitis, pancreatic cancer, or after pancreatic surgery. 1

• Bile Acid Malabsorption: Occurs due to ileal disease or resection, genetic defects in bile acid synthesis feedback, or idiopathic causes. Present in approximately 28% of patients with diarrhea-predominant IBS. 1

• Short Bowel Syndrome (SBS): Results from extensive small intestinal resection, mesenteric infarctions, Crohn's disease, trauma, or radiation damage, leading to reduced absorptive surface area. 1, 2

• Celiac Disease: An immune-mediated enteropathy triggered by gluten exposure in genetically predisposed individuals, causing villous atrophy and malabsorption. One of the most common causes of chronic malabsorption. 1

• Small Intestinal Bacterial Overgrowth (SIBO): Characterized by excessive bacteria in the small intestine interfering with normal digestion and absorption. 1, 3

• Malabsorptive Procedures: Surgical procedures like biliopancreatic diversion with duodenal switch (BPD/DS) can lead to malabsorption of nutrients, especially fat-soluble vitamins. 2

Pathophysiology

• Malabsorption can result from defective luminal digestion due to lack of pancreatobiliary enzymes, or from failure of absorption due to mucosal disease or structural disorders. 2

• Pancreatic exocrine insufficiency is the usual cause of severe steatorrhoea where faecal fat excretion exceeds 13 g/day (47 mmol/day). 2

• In SIBO, bacterial overgrowth results in bile salt deconjugation, less effective secondary bile acids, and pancreatic enzyme degradation, causing steatorrhea and malnutrition. 3

• Malabsorption can affect macronutrients (fats, carbohydrates, proteins) as well as micronutrients (vitamins, minerals). 4

Clinical Manifestations

• Gastrointestinal symptoms: Chronic diarrhea, steatorrhea (fatty stools), abdominal distention, bloating, and weight loss despite adequate caloric intake. 5, 6

• Nutritional deficiencies: Depending on the specific nutrients affected, may include:

  • Fat-soluble vitamin deficiencies (A, D, E, K) 3
  • Mineral deficiencies (calcium, magnesium, iron) 7
  • Protein malnutrition 8

• Specific deficiency manifestations:

  • Vitamin A: Night blindness, poor color vision, dry skin, xerophthalmia 3
  • Vitamin D: Increased risk of fractures, osteomalacia 3
  • Vitamin E: Peripheral neuropathy, ataxia, ophthalmoplegia 3
  • Vitamin K: Easy bruising, prolonged bleeding time, elevated prothrombin time 3

Diagnostic Approach

• Stool studies: Fecal fat measurement to confirm fat malabsorption. Three-day collection of stools has been the standard test for decades, though newer methods are becoming available. 2

• Serological testing: Including IgA anti-tissue transglutaminase (TTG) antibody for celiac disease. 1

• Endoscopy with biopsies: Gold standard for diagnosing celiac disease and other mucosal disorders. Colonoscopy with biopsies to exclude microscopic colitis. 2, 1

• Pancreatic function testing: Including fecal elastase, with levels <100 μg/g indicating exocrine pancreatic insufficiency. 1

• Breath tests: Including hydrogen breath tests for carbohydrate malabsorption, though these have poor sensitivity and specificity for SIBO. 2, 1

• Bile acid malabsorption testing: Includes the SeHCAT nuclear medicine test and serum C4 and FGF19 measurements. 2, 1

Management Principles

• Treat the underlying cause when possible:

  • Gluten-free diet for celiac disease 1
  • Antibiotics for SIBO 9
  • Pancreatic enzyme replacement therapy for PEI 1

• Nutritional support:

  • For patients unable to meet energy needs with oral nutrition alone, enteral nutrition should be tried before parenteral nutrition. 9
  • Home parenteral nutrition should not be delayed in malnourished patients when oral nutrition or enteral nutrition is inadequate. 9

• Specific treatments:

  • Pancreatic Enzyme Replacement Therapy (PERT): Starting dose of 500 units of lipase per kg per meal and 250 units per kg per snack for PEI. 1
  • Bile acid sequestrants: Such as cholestyramine for bile acid malabsorption, though in severe cases, steatorrhea may worsen with this treatment. 2
  • Vitamin supplementation: Higher doses of fat-soluble vitamins for patients with malabsorptive conditions:
    • Vitamin D: 2000-4000 IU daily 1
    • Vitamin A: 10,000 IU daily 1, 3
    • Vitamin E: 100 IU daily 1
    • Vitamin K: 300 μg daily 1
    • Zinc: At least 30 mg daily 1

• Water-miscible forms of fat-soluble vitamins show improved absorption, especially in malabsorption syndromes. 3

• Regular monitoring of nutritional status, electrolytes, and micronutrient levels is essential. 9

Special Considerations

• Malabsorptive bariatric procedures: Patients who have undergone malabsorptive procedures like BPD/DS require higher doses of vitamins and minerals and regular monitoring. 2

• Pregnancy: Women who become pregnant post-bariatric surgery should be treated as a specialist obstetric population with specific needs, including access to specialist dietetic support and close monitoring of nutrition. 2

• Adolescents: A vulnerable group that needs regular monitoring and support through growth and sexual development, especially after bariatric surgery. 2