Diarrhea

Did You Know?

• The word diarrhea comes from Ancient Greek διάρροια, from διά 'through' and ῥέω 'flow'.
• Slang terms include 'the runs', 'the squirts', 'Hershey squirts', 'Montezuma's Revenge', and 'the trots'.
• Diarrhea may function as an evolved expulsion defense mechanism; stopping it with anti-diarrhea drugs could delay recovery, as seen in Shigella treatment.

Definition

Diarrhea is defined by the World Health Organization as having three or more loose or liquid stools per day, or as having more stools than is normal for that person. Acute diarrhea, as defined by the World Gastroenterology Organization, is an abnormally frequent discharge of semisolid or fluid fecal matter from the bowel lasting less than 14 days; when watery, it may be called Acute Watery Diarrhoea (AWD). Secretory diarrhea involves increased active secretion or inhibited absorption with little structural damage, commonly caused by cholera toxin stimulating anion secretion, particularly chloride ions, which draws sodium and water to maintain charge balance; this type continues even without oral food intake. Osmotic diarrhea occurs when excessive water is drawn into the bowels, often from high-sugar or high-salt solutions, maldigestion (e.g., pancreatic disease or coeliac disease), or osmotic laxatives; it stops when the offending agent is removed. Exudative diarrhea features blood and pus in the stool, seen in inflammatory bowel diseases like Crohn's disease or ulcerative colitis, and severe infections such as E. coli or other food poisoning.

Causes

Diarrhea results when the large intestine cannot sufficiently absorb water or digestive fluids from fecal matter, often due to infection or other conditions. Acute diarrhea is most commonly caused by viral gastroenteritis, with rotavirus accounting for 40% of cases in children under five; in travelers, bacterial infections predominate. Mushroom poisoning and drugs can also trigger acute diarrhea. Chronic diarrhea may stem from chronic intestinal conditions such as ulcerative colitis, Crohn's disease, microscopic colitis, celiac disease, irritable bowel syndrome, or bile acid malabsorption. Infectious diarrhea, frequently called gastroenteritis, is caused by viruses (norovirus in adults, rotavirus in children under five, adenovirus types 40 and 41, astroviruses), bacteria (Shiga-toxin producing E. coli, Campylobacter, Salmonella, Shigella, some E. coli strains), and parasites (Cryptosporidium, Giardia, Entamoeba histolytica, Blastocystis, Cyclospora cayetanensis). In the elderly treated with antibiotics, Clostridioides difficile toxin often causes severe diarrhea.

Prevention

Improvements in drinking water and sanitation (WASH), such as water filters, high-quality piped water, and sewer connections, reduce diarrhea risks. Hand washing with soap in institutions, communities, and households significantly lowers incidence, as does preventing open defecation and providing improved sanitation including toilets and the full sanitation chain. Safe disposal of child or adult feces may prevent diarrheal disease. Basic sanitation techniques, like hand washing with soap and water, have been shown experimentally to reduce disease incidence by approximately 30–48%. In developing countries, limited access to soap and water poses a challenge, addressed through educational programs promoting sanitary behaviors. Clean water supply and improved sanitation could cut child mortality from diarrheal disease by 88%; meta-analyses show a 22–27% reduction in incidence and 21–30% reduction in mortality. Chlorine treatment of water reduces both the risk of diarrheal disease and contamination of stored water with pathogens.

Management

Replacing lost fluid and salts, usually by oral rehydration therapy or intravenously in severe cases, is often the only treatment needed. Diet restrictions like the BRAT diet are no longer recommended; research does not support limiting milk for children, and WHO advises continuing to eat to support growth and recovery. CDC recommends that children and adults with cholera continue eating. Medications such as loperamide (Imodium) and bismuth subsalicylate may help but can be contraindicated in certain situations. Oral rehydration solution (ORS), a slightly sweetened and salty water, prevents dehydration; home solutions include salted rice water, salted yogurt drinks, vegetable and chicken soups with salt, or water with half a teaspoon to a full teaspoon of salt per liter. Commercial solutions like Pedialyte and UNICEF packets are available. A WHO publication recommends one liter water with one teaspoon salt and two tablespoons sugar; Rehydration Project suggests half a teaspoon salt with the same sugar, noting this dilute approach is less risky. Drinks with too much sugar or salt can worsen dehydration.