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What is traditionally defined as an increase in daily stool weight in diarrhea?
Chronic diarrhea accounts for 10% of the population.
False
What are the three primary functions of the small bowel?
motility, digestion, absorption
In normal stool fluids processing, the large bowel absorbs approximately _______________ L/d.
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Match the following nutrient/vitamin absorption sites:
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What is the cause of Osmotic Diarrhea?
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Inflammatory Diarrhea is caused by exogenous secretagogues.
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What is the main reason for Diarrhea caused by motility disturbances?
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Osmotic Diarrhea is caused by the ingestion of ______________ osmotically active substances.
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Match the following types of diarrhea with their causes:
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Study Notes
Normal Stool Processing
- The GI system processes 8-9 L/day of stool fluids, with 1-2 L/day ingested and 7 L/day created
- The small bowel reabsorbs 6-7 L/day, and the large bowel absorbs 1-2 L/day
- This results in 100-200 g/day of stool created
- A decrease in absorption or increase in secretion by as little as 1% can lead to diarrhea
Nutrient/Vitamin Absorption
- Carbohydrates/simple sugars are absorbed in the duodenum/jejunum
- Vitamin B12 and short-chain fatty acids are absorbed in the ileum
- Fats, bile salts, and vitamin K are absorbed in the colon
- Amino acids, iron, fat-soluble vitamins (A, D, E, K), calcium, magnesium, and other vitamins and minerals are also absorbed in the GI system
Chronic Diarrhea
- Affects 5% of the population
- Most frequent etiologies include:
- Functional disorders (e.g., irritable bowel syndrome)
- Inflammatory bowel disease (IBD)
- Malabsorptive syndromes
- Chronic infection
Small Bowel Function
- Motility
- Digestion
- Absorption
- Immune defense
Pathophysiology of Chronic Diarrhea
- Types of chronic diarrhea:
- Osmotic diarrhea
- Secretory diarrhea
- Inflammatory diarrhea
- Motility disturbances
Osmotic Diarrhea
- Causes:
- Ingestion of poorly absorbed osmotically active substances (non-electrolytes)
- Carbohydrate malabsorption (e.g., disaccharidase deficiency, glucose-galactose malabsorption, fructose malabsorption)
- Mechanism: retention of unabsorbed ions in the intestinal lumen, leading to water retention to maintain intraluminal osmolality
Secretory Diarrhea
- Causes:
- Exogenous secretagogues (e.g., cholera toxin)
- Endogenous secretagogues (e.g., neuroendocrine tumor)
- Absence of ion transporter (e.g., congenital chloridorrhea)
- Mechanism: increased net flux of ions into the intestinal lumen, leading to secretion of anions (chloride or bicarbonate) and inhibition of sodium absorption
Inflammatory Diarrhea
- Causes:
- Inflammatory bowel disease (IBD)
- Ischemic colitis
- Diverticulitis
- Radiation colitis
- Infectious causes (e.g., invasive bacterial, parasitic, or viral infections)
- Mechanism: structural damage to the intestinal mucosa, impairing absorption and stimulating secretion
Diarrhea - Motility Disturbances
- Causes:
- Abnormal intestinal motility (e.g., hyperthyroidism, dumping syndrome, postvagotomy diarrhea, postsympathectomy diarrhea, diabetic autonomic neuropathy)
- Mechanism: decreased contact between digested food products and the intestinal mucosa, leading to diarrhea
Clinical Classification of Chronic Diarrhea
- Organic vs. functional
- Fatty
- Watery
- Inflammatory
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Description
This quiz covers the causes and characteristics of osmotic and secretory diarrhea, including the role of poorly absorbed substances, ions, and carbohydrates in the development of these conditions.
