RT Book, Section A1 Caicedo, Ricardo A. A1 Hill, Ivor D. A2 Rudolph, Colin D. A2 Rudolph, Abraham M. A2 Lister, George E. A2 First, Lewis R. A2 Gershon, Anne A. SR Print(0) ID 7035769 T1 Chapter 385. Diarrhea T2 Rudolph's Pediatrics, 22e YR 2011 FD 2011 PB The McGraw-Hill Companies PP New York, NY SN 978-0-07-149723-7 LK accesspediatrics.mhmedical.com/content.aspx?aid=7035769 RD 2024/11/13 AB Diarrhea is an increase in the liquidity and/or frequency of the stools. It reflects an increase in stool water content due to impaired water absorption and/or active water secretion by the intestine. Although the advent of oral rehydration therapy has dramatically reduced the mortality rates in the past 50 years, diarrhea remains a major cause of morbidity and mortality in children, particularly among those in developing countries.1 Most episodes of diarrhea occur on the basis of 1 of 5 mechanisms: malabsorptive, secretory, osmotic, dysmotility, and inflammatory. Malabsorption is due to a decrease in absorptive surface area, as occurs after intestinal resection (short bowel syndrome) or with intestinal villous atrophy, as seen in celiac disease. Secretory diarrhea is caused by secretagogues such as bacterial toxins (eg, cholera), gut regulatory peptides (eg, vasoactive intestinal polypeptide), short-chain fatty acids, and bile salts, which can induce intestinal water secretion while inhibiting absorption. Secretory diarrhea characteristically persists even when the patient is in a fasting state. Osmotic diarrhea results from the intraluminal presence of malabsorbed solutes, such as lactose, which exert significant osmotic pressure that results in secretion of water into the intestines. Osmotic diarrhea characteristically decreases or stops completely during fasting. Dysmotility can lead to increased peristalsis, causing diarrhea due to rapid transit, or to decreased peristalsis, leading to bacterial overgrowth as the cause of diarrhea. Inflammatory disorders cause diarrhea by decreasing the mucosal absorptive capacity and/or through disturbances in motility. One or more of these mechanisms may be operative in an individual during an episode of diarrhea.