• Clinical science



Despite the distinct underlying pathological mechanisms of malabsorption and maldigestion, the term malabsorption is used to refer to both disorders in clinical practice. Malabsorption (e.g., celiac disease, lactose intolerance) describes a malfunction of the intestinal wall, resulting in the insufficient absorption of breakdown products. Maldigestion (e.g., exocrine pancreas insufficiency or cholestasis) is caused by an intraluminal disorder (insufficient secretion of pancreatic enzymes or bile), which prevents the adequate breakdown of food in the intestinal lumen. Both disorders can lead to malnourishment, which, in children, may manifest with delayed and inadequate physical development. Adults mainly present with chronic diarrhea, weight loss, and signs of malnutrition (e.g., iron deficiency anemia). Diagnostic tests assess the digestion of individual food components. Management focuses on the underlying disease; e.g., patients with celiac disease should adhere to a gluten-free diet.


Malabsorption disorders can be caused by either the insufficient absorption or digestion of nutrients. The condition can be further defined as global or partial.



Impaired breakdown of food in the intestinal lumen


Impaired absorption of digested food caused by alterations of the intestinal mucosa


Clinical features

General symptoms

  • Global malabsorption
    • Diarrhea (most common), steatorrhea, abdominal distension, flatulence
    • Weight loss, fatigue
    • Additional symptoms of specific deficiencies
  • Partial (isolated) malabsorption: only symptoms specific to individual nutrient deficiencies (e.g., impaired cobalamin absorption with megaloblastic anemia)

Fat-soluble vitamin deficiencies

Vitamins Symptoms Causes Sources

Vitamin A

  • Night blindness
  • Retinopathy
  • Xerophthalmia
  • Xeroderma
  • Liver, kidney, butter, egg yolks
Vitamin D
  • Lack of sun exposure
  • Kidney or liver disease
  • Inadequate intake, fat malabsorption
Vitamin E
  • Insufficient intake, fat malabsorption
  • Meat, eggs, oils, leafy vegetables

Vitamin K
  • Liver failure
  • Fat malabsorption
  • Green vegetables, broccoli, spinach

The fat cat is in the ADEK (pronounced “attic”)

Water-soluble vitamin deficiencies

Vitamins Clinical features Causes Sources

Vitamin B1


  • Beriberi
    • Dry beriberi: symmetrical peripheral neuropathy (sensory and motor), progressive muscle wasting and paralysis, confusion
    • Wet beriberi: high-output cardiac failure (dilated cardiomyopathy), cardiomegaly, edema
    • Infantile beriberi: cardiomegaly, tachycardia, cyanosis; aseptic meningitis with vomiting and seizures
  • Wernicke-Korsakoff syndrome: confusion, ataxia, and nystagmus
  • Leigh syndrome
  • Chronic alcohol consumption
  • Malnutrition, starvation
  • Diarrhea, prolonged vomiting
  • Diuretics, dialysis
  • Bariatric surgery
  • Yeast, pork, whole grain rice (unpolished), cereals, legumes
Vitamin B2 (Riboflavin)
  • Meat, fish, eggs, milk, green vegetables, yeast

Vitamin B3


  • Meat (liver), cereals, seeds, legumes

Vitamin B5

(Pantothenic acid)

  • Insufficient intake

  • Liver, kidney, egg yolks, broccoli, milk

Vitamin B6


  • Meat, nuts, whole grains, vegetables

Vitamin B12


  • Meat and dairy products
Vitamin C (Ascorbic acid)
  • Prolonged insufficient intake
  • Citrus fruits, strawberries, tomatoes, potatoes, cabbage, spinach

Folic acid


  • Megaloblastic anemia: mostly asymptomatic; possibly symptoms of weakness and cardiopulmonary impairment
  • Glossitis
  • Most common vitamin deficiency in the US
  • Green leaves

Other deficiencies




Differential diagnoses

Protein-losing enteropathy

  • Etiology
  • Clinical features: hypoalbuminemia with peripheral edema
    • In cases of systemic diseases, symptoms may be those of the underlying condition.
    • Further gastrointestinal symptoms may occur depending on the underlying disorder.
  • Treatment
    • Treatment of the underlying disease

The differential diagnoses listed here are not exhaustive.


  • Symptomatic treatment
    • Oral supplementation of fluid, nutrients, and vitamins
    • Calorie and protein-enriched diet
    • IV nutrition in severe cases (e.g., following extensive intestinal resection)
  • Causal treatment of the underlying disease