Diarrhea associated with nutrient malabsorption (malabsorptive diarrhea) is seen with almost all malabsorption syndromes. It is sometimes classified as a type of diarrhea, along with osmotic, secretory and exudative diarrhea, but malabsorption largely contributes to the development of osmotic diarrhea, secretory diarrhea to some extent, and leads to exudative diarrhea. Malabsorption is usually a sub-acute or chronic condition and therefore presents as chronic diarrhea.
The gastrointestinal tract is designed to carry out three main functions :
- Digest food – mechanical and chemical break down of food into simpler compounds
- Absorb nutrients – transport of compounds from the lumen of the gut into the blood stream
- Eliminate wastes – undigested and unabsorbed materials, waste products and water are evacuated through the anus
The process of digestion starts in the mouth but primarily occurs in the stomach and small intestine. Absorption may also start in the mouth and continues throughout the gut although the majority occurs in the small intestine. The lymphatic system is responsible for transporting absorbed fats from the lining of the gut to the blood stream.
How does malabsorption occur?
Malabsorption stems from either defective digestion, defective absorption or lymphatic obstruction. Maldigestion does not allow for foods to be broken down into simpler compounds which can then be absorbed into the blood stream from the gut lumen. With defective absorption, the transport of nutrients across the epithelial lining may be disturbed for various reasons like damage of the epithelium thereby allowing nutrients to remain in the gut. In terms of lymphatic obstruction, the transport of fats is disrupted thereby preventing any fat absorption from the gut.
The presence of these unabsorbed nutrients in the gut affects the osmotic gradient and therefore water absorption from the gut. This leads to osmotic diarrhea as described under runny bowel movements. The unabsorbed nutrients also serve as an additional source of food for intestinal and pathogenic bacteria. This disrupts the normal intestinal flora and can lead to exudative diarrhea.
Types of Malabsorption Disorders
Some of the more common types of disorders that affect digestion, absorption and/or lymphatic drainage.
- Celiac disease
- Tropical sprue
- Infectious gastroenteritis
- Disaccharidase deficienc
- Inflammatory bowel disease
- Lymphatic obstruction
- Whipple disease
Signs and Symptoms
The signs and symptoms may vary depending on the type of nutrient absorption that is compromised – fats, fat-soluble vitamins, water-soluble vitamins, proteins, carbohydrates, electrolytes and minerals. Ultimately water absorption is also affected.
Diarrhea is defined as passing more than 200 grams / 200 milliliters of stool in a day. This occurs within 3 or more bowel movements in a day. The stool is usually loose or watery in consistency. With malabsorption diarrhea, steatorrhea is almost always evident. The stool may appear yellow to pale, greasy and tends to float. Read more on fatty stool.
Excessive flatulence, borborygmi (stomach noises) and abdominal distension usually accompanies the diarrhea and intensifies significantly when consuming foods that cannot be digested or absorbed. Over time there will be loss of appetite, weight loss and muscle wasting. Various symptoms associated with nutrient deficiencies (macro- and micro) will become evident. Read more on vitamin deficiencies.