Different Types of Diarrhea, Loose Stool and Bowel Movements

Diarrhea is a symptom of underlying gastrointestinal dysfunction. It is defined as the passage of more than 200g or 200ml of stool in three or more bowel movements within a 24 hour period. Typically there is a large volume of watery stool especially in acute diarrhea. Sometimes changes in bowel habit and stool form may not fit into the definition of diarrhea yet it is not normal for the individual. Frequent bowel movements and loose stool are two more commonly used terms to describe  these changes but may be used quite subjectively. Irrespective of the terminology, the changes are due to certain known mechanisms.

Diarrhea may be classified as acute or chronic, infectious or non-infectious. Further classification, primarily by cause, can be quite extensive. However, this does not always explain the mechanism of action.

Rapid Transit Time

Diarrhea, frequent bowel movements or loose stool may occur when the bowel transit time is abnormally rapid. This is the time for food from the mouth to pass through the gut and undigested and unabsorbed remnants to pass out as feces. Diarrhea due to changes in bowel transit time is broadly referred to as motility diarrhea. It rarely occurs on its own without one of the three other mechanisms described below as the reduced contact time with the bowel walls means water as well as nutrients are not fully absorbed.

Diarrhea Classification

Diarrhea is often classified as osmotic, secretory or exudative. This describes the mechanism behind the change in bowel frequency and stool consistency.  A fourth type of category is sometimes included and this is malabsorptive but it is similar to osmotic.

Osmotic Diarrhea

Osmotic diarrhea means that substances within the gut are pulling water into the bowel. This may be seen with certain foods and can therefore include the category of malabsorptive diarrhea. One of the common substances that cause osmotic diarrhea is sorbitol. Since it widely found in gum, this type of diarrhea is also commonly know as “chewing gum” diarrhea. The bowel does secrete some amount of water into the bowels to help with motility and digestion. Water that is normally reabsorbed in the large intestine instead remains and is passed out with the stool.

Secretory Diarrhea

Secretory diarrhea means that the bowels pass out water from its tissue spaces into the lumen of the bowel. The body essentially loses water and the stool is typically large volume and watery. This types of diarrhea is more commonly seen with the use of certain medications and infections. It overlaps with exudative diarrhea at times. Secretory diarrhea can lead to loss of large volumes of water and electrolytes that can quickly lead to dehydration.

Exudative Diarrhea

This type of diarrhea is associated mainly with infections. It is characterized by the presence of blood or pus in the stool. The infections implicated in exudative diarrhea may be severe and this type of diarrhea can also be arise with a complication in an infection that initially presents with secretory diarrhea. A non-infectious cause of exudative diarrhea is inflammatory bowel disease, particularly ulcerative colitis. Here extensive inflammation of the bowel wall compromises its ability to reabsorb water and prevent water loss.

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