Knowra Osmotic diarrhea Osmotic diarrhea Osmotic diarrhea is loose, watery stool caused by poorly absorbed substances that retain water in the intestinal lumen. It typically improves when the triggering substance is stopped or during fasting.
Osmosis : The net movement of water across a selectively permeable membrane toward the side with higher effective solute concentration. Poorly absorbed luminal solutes create the osmotic gradient that retains water in the intestine.
Lactose intolerance : Digestive symptoms caused by inadequate digestion of lactose, usually because intestinal lactase activity is low. Undigested lactose retains water in the gut and can trigger osmotic diarrhea.
Secretory diarrhea : Watery diarrhea caused by intestinal secretion or impaired absorption of electrolytes, often persisting during fasting. Its persistence without food contrasts with the usual improvement of osmotic diarrhea during fasting.
Chronic diarrhea : Diarrhea lasting at least four weeks, with causes that include malabsorption, inflammation, infection, and altered gut function. Osmotic diarrhea is one mechanism considered when watery stools persist.
Intestinal absorption : The movement of nutrients, water, and electrolytes from the intestinal lumen into the body. Impaired absorption leaves solutes behind to drive water retention.
Lactase deficiency : Reduced activity of lactase, the small-intestinal enzyme that splits lactose into glucose and galactose. It leaves lactose available to exert osmotic force and undergo bacterial fermentation.
Inflammatory diarrhea : Diarrhea caused by intestinal mucosal inflammation, often accompanied by blood, mucus, fever, or pain. Inflammation damages the mucosa, rather than unabsorbed solutes being the primary driver.
Stool analysis : Laboratory examination of stool to assess its composition and identify evidence of infection, inflammation, bleeding, or malabsorption. Electrolyte measurements can help estimate the fecal osmotic gap.
Small intestine : The digestive tract segment between the stomach and large intestine, where most nutrient absorption occurs. Unabsorbed carbohydrates and other solutes often begin their osmotic effect here.
Fructose malabsorption : Incomplete absorption of dietary fructose in the small intestine, which can cause gastrointestinal symptoms. Unabsorbed fructose can draw water into the lumen and contribute to loose stools.
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