Causes of Malabsorption Quiz

Causes of Malabsorption

• Small intestinal disease or resection:
  • Small bowel disease can impair the enterohepatic circulation of bile salts, leading to malabsorption
  • Resection of the small bowel can also lead to malabsorption
• Small intestinal bacterial overgrowth:
  • Bacterial overgrowth can lead to deconjugation of bile acids, impairing fat absorption
• Pancreatic exocrine insufficiency:
  • Impaired production of pancreatic enzymes due to chronic pancreatitis or cystic fibrosis can cause malabsorption
• Disorders of bile acid metabolism:
  • Inadequate synthesis (e.g., cirrhosis) can lead to malabsorption
  • Inadequate secretion of bile salts (e.g., cholestasis) can also cause malabsorption
  • Inadequate delivery of bile (e.g., biliary obstruction) can impair fat digestion
• Other causes:
  • Abetalipoproteinemia: A rare inherited disorder that impairs the packaging and secretion of chylomicrons, leading to fat malabsorption
  • Abnormalities in lymphatic flow: Conditions like intestinal lymphangiectasia, tuberculosis, and lymphoma can affect lymph flow, leading to malabsorption

Protein Digestion and Absorption

• Protein digestion begins in the stomach with the action of gastric pepsins
• Amino acid release stimulates the release of cholecystokinin (CCK) from the duodenum and jejunum
• CCK stimulates the release of pancreatic enzymes responsible for the digestion of all macronutrients
• In the duodenum, proteases digest proteins into amino acids, dipeptides, and tripeptides
• These products are absorbed at the brush border membrane
• Different classes of amino acid transporters exist on the brush border

Cardinal Symptoms of Malabsorption

• Steatorrhea: Pale, greasy, foul-smelling, frothy, bulky stools that are difficult to flush due to increased fat content

Causes of Protein Malabsorption

• Impaired secretion of pancreatic bicarbonate and protease:
  • Pancreatic insufficiency due to cystic fibrosis or chronic pancreatitis
• Impaired activity of enzymes:
  • Decreased intestinal absorptive surface area
• Gastric, pancreatic, or small bowel resection:
  • Loss of sites of secretin and CCK synthesis and inadequate mixing of chyme with pancreatic enzymes

Management of Malabsorption

• Treat the underlying disease
• Optimize control of diarrhea
• Identify and treat nutritional deficits
• Optimize quality of life
• Multidisciplinary team (MDT) approach: Dietician, gastroenterologist, speech language therapist (SLT)
• Diarrhoea: Antidiarrhoeals (eg.Loperamide)
• Dietary modifications: Avoidance of triggers (e.g., FODMAPS)
• Supplementation: Fat-soluble vitamins, calcium, magnesium, iron, folate, vitamin B12, and zinc
• Based on aetiology:
  • Bile acid malabsorption: Therapy with exogenous conjugated bile acids or cholestyramine
  • Small intestinal bacterial overgrowth: Antibiotics

Differential Diagnosis of Malabsorption

• Based on Malabsorptive Defect*

• Luminal Phase:

  • Digestive enzyme deficiency: Chronic pancreatitis
  • Digestive enzyme inactivation: Zollinger-Ellison syndrome
  • Dyssynchrony of enzyme release: Post Bilroth II procedure
  • Fat solubilisation:
    • Diminished bile salt synthesis: Cirrhosis
    • Impaired bile secretion: Chronic cholestasis
    • Bile salt de-conjugation: Bacterial overgrowth
    • Increased bile salt loss: Ileal disease or resection

• Luminal Availability of Specific Nutrients:

  • Diminished gastric acid: Atrophic gastritis (B12 deficiency)
  • Diminished intrinsic factor: Pernicious anemia (B12 deficiency)
  • Bacterial consumption of nutrients: Bacterial overgrowth (B12 deficiency)

• Mucosal (Absorptive) Phase:

• Investigation*

• In individuals with a history of pancreatitis, excessive alcohol use, or low fecal elastase:

  • Fecal elastase
  • Imaging of the pancreas with magnetic resonance cholangiopancreatography (MRCP)
  • Endoscopic ultrasound evaluation

• In patients with predisposing risk factors for bacterial overgrowth (e.g., strictures, adhesions, small bowel diverticulosis, blind intestinal loops):

  • Breath test for small bacterial overgrowth

• In patients without an identifiable cause or risk factors:

  • Upper endoscopy and colonoscopy with multiple mucosal biopsies (e.g., to rule out Crohn's disease)
  • Imaging of the small bowel with computed tomography (CT) or magnetic resonance (MR) enterography
  • D-xylose test

• Bloods*

• Serologic testing for celiac disease: Anti-TTG, Anti-EMA

• Fecal elastase to exclude maldigestion due to pancreatic insufficiency

• Endoscopy with Biopsy*

• Macroscopic features on endoscopy may suggest the presence of an underlying cause of malabsorption

• Intestinal biopsies are usually required to confirm the aetiology

• For example:

  • Cobblestone appearance of the duodenal mucosa is seen in Crohn's disease
  • Reduced duodenal folds and scalloping of the mucosa may be evident in celiac disease
  • Multiple jejunal ulcers may indicate the presence of jejunoileitis, a gastrinoma, or infiltrative disease (e.g., lymphoma)

• Imaging*

• Small bowel: Upper gastrointestinal series with small bowel follow-through, or a CT or MR enterography, wireless video capsule endoscopy help identify small bowel diverticulae or other anatomic abnormalities associated with bacterial overgrowth

• Pancreas: Pancreatic imaging by CT or MRCP may be helpful in the diagnosis of chronic pancreatitis and may be critical for distinguishing benign from malignant causes

• Secretin stimulation remains the most sensitive means of diagnosing pancreatic insufficiency

• Breath Tests*

• Small intestinal bacterial overgrowth: The diagnosis of SIBO is supported by a positive glucose or lactulose breath test, or a positive jejunal aspirate culture (gold standard)

• Malabsorption of specific carbohydrates: Breath tests are available to assess the integrity of lactose, fructose, and sucrose absorption

• Other Infrequently Performed Tests*

• D-xylose absorption test for small bowel mucosal disease

• Protein malabsorption testing is rarely performed

• Bile acid malabsorption: Evaluation with a SeHCAT test can differentiate bile acid diarrhea from diarrhea due to fat malabsorption

  • A therapeutic trial with a bile acid-binding resin (e.g., cholestyramine) can be used to support the diagnosis of cholorrhea

Malabsorption

• Malabsorption is a general term describing impaired absorption of nutrients, encompassing fats, carbs, proteins, vitamins, electrolytes, minerals and water
• It often presents with chronic diarrhea
• Normal nutrient absorption involves three phases: luminal processing, absorption into the intestinal mucosa, and transport into circulation
• Malabsorption can arise from defects in any of these three phases

Causes of Malabsorption

• Global Malabsorption:
  • Affects the mucosa or causes reduced absorption area
  • Prevents adequate nutrient absorption
  • Example: Celiac disease
• Partial Malabsorption:
  • Localized disease that interferes with absorption of specific nutrients
  • Example: B12 deficiency in pernicious anemia
• Selective Malabsorption:
  • Specific deficiency of a nutrient
  • Example: primary lactase deficiency
• Primary Malabsorption (Congenital):
  • Due to congenital defects in membrane transport systems
• Secondary Malabsorption (Acquired):
  • Results from acquired defects in the epithelial absorptive surface
  • Examples: Crohn disease, celiac disease, extensive surgical resection, intestinal bypass operations

Fat Digestion and Absorption

• Bile acid metabolism cycle involves the liver, gallbladder, and small intestine
• Bile acids are essential for fat digestion and absorption

Causes of Fat Malabsorption

• Small Intestinal Disease/Resection:
  • Small bowel disease or resection impairs fat absorption
  • Impairment of the enterohepatic circulation of bile salts
• Small Intestinal Bacterial Overgrowth:
  • Bacteria deconjugate bile acids, interfering with fat absorption
• Pancreatic Exocrine Insufficiency:
  • Impaired production of pancreatic enzymes due to chronic pancreatitis or cystic fibrosis
  • This impairs fat digestion
• Disorders of Bile Acid Metabolism:
  • Inadequate bile acid synthesis (e.g., cirrhosis)
  • Inadequate secretion of bile salts (e.g., cholestasis)
  • Inadequate delivery of bile (e.g., biliary obstruction due to tumor or stone)
• Other Causes:
  • Abetalipoproteinemia: Rare inherited disorder affecting chylomicron synthesis and secretion, impairing fat absorption
  • Abnormalities in lymphatic flow: Examples include intestinal lymphangiectasia, tuberculosis, and lymphoma

Cardinal Symptoms of Malabsorption

• Steatorrhea: Pale, greasy, foul-smelling, frothy, bulky stools difficult to flush due to increased fat content

Protein Digestion and Absorption

• Protein digestion begins in the stomach with gastric pepsin
• Amino acids released stimulate cholecystokinin (CCK) production, leading to pancreatic enzyme release for protein digestion
• Proteases further break down proteins in the duodenum
• Amino acids, dipeptides, and tripeptides are absorbed at the brush border membrane

Causes of Protein Malabsorption

• Impaired pancreatic protease and bicarbonate secretion (e.g., cystic fibrosis, chronic pancreatitis)
• Reduced intestinal absorptive surface

Signs and Symptoms of Malabsorption

• Malabsorption of:
  • Calories: Weight loss with normal appetite
  • Fat: Steatorrhea, Fractional fat excretion
  • Protein: Edema, muscle atrophy, Hypoalbuminaemia, hypoproteinaemia
  • Carbohydrates: Watery diarrhea, flatulence, Increased breath hydrogen
  • B12: Anemia, macrocytic anemia, low B12 levels
  • Folate: Anemia, macrocytic anemia
  • Vitamin B: Cheilosis, glossitis, angular stomatitis, acrodermatitis
  • Iron: Anemia, glossitis, microcytic anemia, decreased serum iron, ferritin, and transferrin saturation
  • Calcium and Vitamin D: Parasthesia, tetany, osteomalacia, Chvostek's and Trousseau's signs, hypocalcaemia, increased alkaline phosphatase, abnormal bone densiometry
  • Vitamin A: Follicular hyperkeratosis, night blindness, Decreased serum retinol
  • Vitamin K: Bleeding, bruising, Low vitamin K dependent coagulation factors

Assessment and Investigative Work-up

• Investigations Guided by History
• Coeliac Disease: Anti-TTG (tissue transglutaminase), Anti-EMA (Endomysial antibody)
• Pancreatic Insufficiency: Faecal elastase, Imaging of the pancreas (e.g., MRCP), Endoscopic ultrasound evaluation
• Bacterial Overgrowth: Breath test for small bacterial overgrowth
• Unknown Cause: Upper endoscopy and colonoscopy with biopsies, Small bowel imaging (CT or MR enterography)
• D-xylose test: distinguishes mucosal disease from maldigestion
• Bloods: Serologic testing for coeliac disease, faecal elastase
• **Endoscopy with Biopsy: ** Identify underlying causes of malabsorption (e.g., Crohn's disease, celiac disease, jejunoileitis, gastrinoma, lymphoma)
• Imaging: Small bowel (upper GI series, CT or MR enterography, wireless video capsule endoscopy), Pancreas (CT or MRCP)
• Breath Tests: Small intestinal bacterial overgrowth, Malabsorption of specific carbohydrates
• Other tests: D-xylose absorption test, Protein malabsorption, Bile acid malabsorption (SeHCAT test)

Management

• Treat the underlying disease
• Optimize control of diarrhea
• Identify and treat nutritional deficits
• Monitor for re-occurrence
• Optimize quality of life

Management Approach

• Multidisciplinary team approach: Dietician, gastroenterology, Speech and Language Therapist (SLT)
• Diarrhoea: Antidiarrhoeals (e.g., Loperamide) only after ruling out infection
• Dietary Modifications: Avoidance of trigger foods, such as FODMAPs
• Supplementation: Fat-soluble vitamins, calcium, magnesium, iron, folate, vitamin B12, and zinc
• Aetiology-specific therapies:
  • Bile acid malabsorption: Exogenous conjugated bile acids and cholestyramine
  • Small intestinal bacterial overgrowth: Antibiotics to reduce bacteria

Test your understanding of the various causes of malabsorption, including intestinal diseases, pancreatic insufficiency, and bile acid metabolism disorders. Explore the impact of small bowel resection and bacterial overgrowth on nutrient absorption. This quiz will help consolidate your knowledge on gastrointestinal health.