kolhydratmalabsorption

Kolhydratmalabsorption, or carbohydrate malabsorption, is a condition in which the small intestine cannot adequately digest or absorb certain carbohydrates. This leads to an accumulation of osmotically active substances in the lumen, increased fermentation by gut bacteria, and symptoms such as bloating, abdominal pain, gas, and diarrhea. It can involve one or several carbohydrates, including lactose, fructose, sorbitol, and others.

Common causes include lactase deficiency (primary lactase non-persistence or secondary loss from mucosal injury), sucrase-isomaltase deficiency, pancreatic exocrine insufficiency, and small intestinal bacterial overgrowth. Mucosal diseases such as celiac disease or inflammatory bowel disease, surgical resection of the small intestine, and certain medications can also contribute. Fructose and sorbitol malabsorption may occur independently or alongside lactose intolerance.

The pathophysiology typically involves reduced enzymatic activity or damaged absorptive surface, resulting in undigested carbohydrates reaching the colon. There, bacteria ferment them, producing gas and short-chain fatty acids, and the undigested sugars draw water into the lumen, causing diarrhea.

Diagnosis relies on clinical history and noninvasive tests. Hydrogen breath tests can assess lactose, fructose, or other carbohydrate malabsorption. Additional tests may include genetic testing for lactase persistence, measurement of lactase activity in intestinal biopsy samples, stool studies, and evaluation for underlying conditions such as celiac disease or pancreatic insufficiency.

Management centers on dietary modification and symptom relief. Lactose- or fructose-restricted diets, or a broader low-FODMAP approach, may reduce symptoms. Enzyme supplements (e.g., lactase) can help some individuals, and treatment of associated conditions and pancreatic insufficiency is important. Prognosis improves with appropriate dietary management and treatment of any underlying disease. Epidemiology varies by carbohydrate type and population.