DESCRIPTION

Malabsorption is characterized as a syndrome, as opposed to a disease entity, and is defined as impairment of digestion and/or absorption of nutrients across the intestinal mucosa. It is caused by either a congenital or acquired disorder. Classic symptoms of malabsorption include chronic diarrhea, failure to thrive, and nutrient deficiencies.

EPIDEMIOLOGY

Dependent on the underlying disease causing malabsorption

ETIOLOGY

• The most common causes of malabsorption in developed countries are as follows:
  • Celiac disease (most common inherited malabsorption syndrome; prevalence of 1%)
  • Cystic fibrosis
  • Postenteritis syndrome
  • Cow’s milk protein allergy
  • Giardiasis
  • Inflammatory bowel disease (IBD)
• Other causes based on type of macronutrient malabsorbed include the following:
  • Carbohydrate
    • Monosaccharide: congenital glucose-galactose deficiency, fructose intolerance
    • Disaccharide: lactase deficiency (congenital or acquired), sucrase-isomaltase deficiency
    • Polysaccharide: amylase deficiency (congenital or acquired)
  • Fat
    • Bile salt deficiency: cholestasis, terminal ileum resection
    • Exocrine pancreatic insufficiency: cystic fibrosis, chronic pancreatitis
  • Protein
    • Protein-losing enteropathy: intestinal lymphangiectasia, congenital heart failure
    • Exocrine pancreatic insufficiency: cystic fibrosis, chronic pancreatitis

RISK FACTORS

Disorders causing impaired digestive enzyme function or availability (cystic fibrosis), impaired integrity of the gastrointestinal mucosa (IBD, celiac disease), increased intestinal transit time, decreased intestinal length, or short bowel syndrome

GENERAL PREVENTION

Identification of the underlying etiology is required to target prevention. Patients may require removal of an offending dietary component, the use of specific formulas, such as elemental formulas, or the use of parenteral nutrition.

PATHOPHYSIOLOGY

Varies depending on whether malabsorption affects all nutrients or specific components and on the phase of digestion affected; absorption and digestion occur in three phases:

• Intraluminal: enzyme hydrolysis of macronutrients; enzyme deficiencies and stasis or bile acid deconjugation affect this phase.
• Mucosal: digestion by brush border enzymes; disorders affecting brush border integrity and absorptive surface area affect this phase.
• Transport: uptake of nutrients; disorders causing lymphatic or vascular insufficiency affect this phase.