Osmotic diarrhea typically results from one of two situations:
•Ingestion of a poorly absorbed substrate: The offending molecule is usually a carbohydrate or divalent ion. Common examples include mannitol or sorbitol, epson salt (MgSO4) and some antacids (MgOH2).
•Malabsorption: Inability to absorb certain carbohydrates is the most common deficit in this category of diarrhea, but it can result virtually any type of malabsorption. A common example of malabsorption, afflicting many adults humans and pets is lactose intolerance resulting from a deficiency in the brush border enzyme lactase. In such cases, a moderate quantity of lactose is consumed (usually as milk), but the intestinal epithelium is deficient in lactase, and lactose cannot be effectively hydrolyzed into glucose and galactose for absorption. The osmotically-active lactose is retained in the intestinal lumen, where it "holds" water. To add insult to injury, the unabsorbed lactose passes into the large intestine where it is fermented by colonic bacteria, resulting in production of excessive gas.
Dianogsis:
•A careful history and physical examination -- travel, food intolerances, etc., may give clues.
•Stool tests: stool checked for --
1.Fecal leukocytes
2.Ova & parasites
3.Stool osmolality
4.24-hour stool collection for weight and fecal fat
5.Stool laxative screen
Treatment:
•Treat the cause, e.g., lactose deficiency (dietary restriction on dairy products)
•General treatment:
1.In many cases of diarrhea, replacing lost fluid and salts is the only treatment needed. This is usually by mouth – oral rehydration therapy – or, in very severe cases, intravenously.
2.Diet restriction, to known well-tolerated foods, and the BRAT diet and its extensions, may be used for 1-to-3 days.However, limiting milk to children has no effect on the duration of diarrhea.
3.Medicines such loperamide (Imodium), bismuth subsalicylate (as found in Pepto Bismol and Kaopectate) may be beneficial, however they may be contraindicated in certain situations. Prescribed medications sometimes contain pain-killers, such as morphine or codeine, to counter the cramps that can accompany diarrhea.