Malabsorption syndromes

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Malabsorption syndrome refers to a number of disorders in which the small intestine can’t properly absorb one or more nutrients. This may be due to impaired absorption or impaired digestion.

Fat malabsorption is the most common specific nutrient malabsorption.

Etiology

  • Global/complex nutrient malabsorption
    • Exocrine pancreatic insufficiency (chronic pancreatitis, pancreatic duct obstruction, CF)
    • Intestinal resection
    • Inflammatory bowel disease
    • Coeliac disease
    • Gastroenteritis
  • Fat malabsorption
    • Cholestasis
    • Bile acid malabsorption
    • Orlistat
  • Carbohydrate malabsorption
    • Lactose intolerance

Clinical features

Intestinal symptoms include diarrhoea, steatorrhoea (in fat malabsorption), bloating, and abdominal pain. In some cases, extraintestinal symptoms like anaemia, weight loss, nutrient deficiency, and oedema may develop. Some symptoms are specific to certain types of malabsorption:

  • Fat malabsorption – pale stool, steatorrhoea
  • Protein malabsorption – oedema, muscle atrophy
  • Carbohydrate malabsorption – water diarrhoea, flatulence

Diagnosis and evaluation

Many tests can be useful in the evaluation of malabsorption:

  • Serum ferritin – marker of iron absorption
  • Serum protein and albumin– marker of protein absorption
  • Microscopic examination of fat content in stool – marker of fat absorption
  • Hydrogen breath test – test for carbohydrate absorption
    • After consumption of a carbohydrate (usually lactose), serial measurements of hydrogen in the breath are made. Abnormally high levels of hydrogen in the breath in a sign of malabsorption of that carbohydrate
  • D-xylose absorption test – test for small bowel mucosal defects
    • D-xylose is passively absorbed through healthy bowel mucosa. If, following administration of this monosaccharide, serum and urine levels are low, it can be concluded that the bowel mucosa has defects
  • Stool culture – for parasites which impair absorption
  • Bile salt breath test/SeHCAT test – test for bile salt absorption, no longer used
  • Shilling test – test for B12 absorption, no longer used