Diarrhea in Childhood

Warren P. Bishop, M.D.
Associate Professor
Department of Pediatrics
The University of Iowa

First Published: May 2003
Last Revised: May 2003
Peer Review Status: Internally Peer Reviewed

Childhood diarrhea is a common problem encountered by primary care providers. Acute diarrhea in North America is typically viral in etiology, Is usually self-limited, and requires no specific therapy. For these reasons, diagnostic studies are often not required or indicated. When bacterial infection is suspected, antibiotic therapy may be warranted, as discussed below, and stool cultures or other diagnostic testing is generally required. Otherwise, simple supportive care to prevent dehydration and electrolyte abnormalities is all that is needed for acute diarrhea illness.

Chronic diarrhea, on the other hand, has a much broader differential diagnosis. Despite this, most cases of chronic diarrhea are not caused by serious underlying pathology. It is important that clinicians caring for children have a good understanding of the pathophysiology of acute and chronic diarrhea, to be able to use history and physical examination to make an initial diagnosis, and to understand when testing should be done and which tests to use.

What is diarrhea?
We all have our own ideas about what diarrhea is, but how can it be defined objectively? Parents describing "diarrhea" usually are describing a liquid-textured stool. Sometimes, they might mean excessively frequent stools, or are concerned with the volume of each bowel movement (especially when children are in diapers!), even if the frequency of defecation is normal. The strict definition of diarrhea is excessive daily stool volume, more than the upper limit of around 10 ml/kg/day. It is certainly possible to have diarrhea by this definition with stools that are at least partially formed, or to not have diarrhea even with liquid bowel movements. As a practical matter, it is seldom possible for a physician to determine exactly how many grams per day of stool a child is having. You must therefore use the history to estimate for yourself whether true diarrhea is present. The history will usually provide most of the information you will require to classify the diarrhea by type and to consider the diagnostic approach.

How can I classify various types of diarrhea?
How can I use this classification to help me understand my patient's illness?
Diarrhea can be classified several different ways, as summarized in Table 1. Physiologically, diarrhea may result from excessive secretion of water and electrolytes (secretory diarrhea), by malabsorption of osmotically-active ingested substances (malabsorptive or osmotic diarrhea), or often by both mechanisms operating together. It may also be defined by etiology as infectious, inflammatory, or neither.

Secretory diarrhea may be stimulated by infection or inflammation. Cholera is the classic example of massive secretory diarrhea, and is caused by cholera toxin directly stimulating intestinal secretion of water and electrolytes. A much more common cause of secretory diarrhea in the developed world is intestinal inflammation, as observed with ulcerative colitis and Crohn's disease. In this case, cytokines, other pro-inflammatory molecules such as prostaglandins, and enteric hormones released during inflammation are responsible for secretion. Regardless of the underlying cause, secretory diarrhea yields watery stools with a relatively high electrolyte content. Secretory diarrhea continues even when fasting.

Osmotic diarrhea commonly results from intestinal injury, dietary indiscretions, or specific defects in digestion leading to malabsorption of food. Celiac disease is a relatively common example of intestinal injury causing malabsorption. Cystic fibrosis causes maldigestion of fats and proteins, resulting in diarrhea. Osmotic diarrhea also can be caused by the ingestion of non-digestible or non-absorbable substances. Laxatives such as magnesium salts, polyethylene glycol, and lactulose all fit this category. When a specific digestive enzyme is lacking, as in lactose intolerance, osmotic diarrhea results only when the substrate of that enzyme (lactose) is eaten. Overindulgence of certain foods for which we have limited absorptive capacity can also cause diarrhea. A common example is the watery diarrhea seen with excessive intake of fructose in fruit juices or soft drinks. Stools in osmotic diarrhea have a relatively low electrolyte content, because the osmolarity of the stool is largely accounted for by the malabsorbed material. Osmotic diarrhea ceases when enteral intake is withheld.

Etiologic classification: Another way to classify diarrhea is by cause-infectious vs. noninfectious, or inflammatory vs. non-inflammatory. Fever, bloody diarrhea, and severe cramping (dysentery) suggest an invasive bacterial pathogen such as Shigella, Salmonella, Yersinia, or Campylobacter, or amebic dysentery. Coexistence of other signs or symptoms (arthritis, perianal fistulae, chronic weight loss) with diarrhea may suggest inflammatory bowel disease. Viral agents cause extensive injury to small intestinal epithelium but not deep tissue invasion, yielding watery, voluminous stools. It is useful to keep each of these different etiologic and physiologic classifications in mind as you evaluate the nature of your patient's illness.

Table 1. Types of Diarrhea
Classification	History
Secretory vs. Osmotic (malabsorptive)	Continues when NPO, high stool electrolyte content Worse with intake of malabsorbed substance, failure to thrive when malabsorption is generalized, low stool electrolyte concentration, ceases when intake is withheld.
Infectious vs.     Noninfectious	Fever, blood in stools (with invasive bacterial etiology), history of exposure, associated nausea and vomiting (rotavirus and other viral agents), prior antibiotic use (Clostridium dificile) Lack of above. History of dietary cause, history suggesting chronic inflammatory condition (see below)
Inflammatory vs.   Non-inflammatory	Long duration, associated signs of inflammatory disease (arthritis, rash, perianal lesions, etc.), failure to thrive Absence of above

What are the common causes of acute diarrhea in children?
Table 2 lists common causes of acute diarrhea. Of the infectious agents, rotavirus is the most frequent. This is seen mostly during the winter months and also is accompanied by vomiting.

Table 2. Conditions causing acute diarrhea
Viral agents: Bacterial agents: rotavirus, calcivirus, adenovirus, Norwalk virus, astrovirus	Bacterial agents: Campylobacter, Salmonella, Shigella, pathogenic E. coli, Clostridium dificile Vibrio cholerae	Parasites: Giardia, ameba, Cryptosporidium
Lactose intolerance	Laxative ingestion	Allergy

What are the common causes of chronic diarrhea in children?
Refer to Table 3 for help with this one. The causes of chronic diarrhea differ significantly from those of acute diarrhea. Many of these conditions have predominant features of osmotic diarrhea. The major clues to these are found in the dietary history in some cases. Others have no striking association with particular types of intake, especially when serious intestinal injury (celiac disease) or lack of multiple digestive enzymes is the cause (cystic fibrosis). Many types of diarrhea have features of both malabsorption and secretion. For example, the cytokines released by lymphocytes in inflammatory bowel disease typically stimulate secretory diarrhea, while the associated bowel injury may lead to malabsorption.

Table 3: Common Causes of Chronic Diarrhea
Diagnosis	Symptoms
Toddler's diarrhea- excessive intake of sweet clear liquids	Copius watery stools, large intake of sweet clear-liquid beverages.
Lactose intolerance	Watery stools and flatulence following ingestion of non-fermented dairy products. Often a temporary result of injury caused by viral enteritis. In older children, may simply be onset of 1 degree lactase non-persistence (adult lactose intolerance).
Pancreatic insufficiency (Cystic fibrosis, Schwachman-Diamond syndrome)	Greasy, foamy, extremely foul-smelling stools due to maldigestion of fat and protein.
Short bowel syndrome	Generalized malabsorption due to diminished surface area. Stools typically acidic and watery with smaller fat and protein component than seen with pancreatic insufficiency
Celiac disease	Similar to short bowel syndrome, but typically less severe. Diarrhea not always present, depending on severity and extent of intestinal injury
Laxative use	Watery stools due to osmotic action of laxative.
Parasite (Giardia, Cryptosporidium)	Watery, often foul-smelling stools with cramping. Strong secretory component--diarrhea persists when NPO.
Irritable bowel syndrome	Watery stools typical of secretory diarrhea, often alternating with more normal stools. Associated with cramp abdominal pain.
Inflammatory bowel disease	Watery stools, often with blood and mucus, associated with cramps. May have failure to thrive, arthritis, or other extraintestinal symptoms
Allergic enteritis	Chronic diarrhea, often with blood and mucus. Presence of eosinophils on fecal smear and in biopsies of intestine. Symptoms gradually relieved upon exclusion of offending antigen.

Take particular note of "toddler's diarrhea."
This condition got its name because of the tendency for young children to drink large quantities of sweet, clear liquids. This results in a large fluid and osmotic load. Because the intestinal capacity for absorption of fluid and carbohydrates is finite, watery diarrhea results. These children do not have generalized malabsorption, and are thriving. Their parents are typically particularly aware of the loose stools when the children are still in diapers, a messy and unpleasant situation!

How can I differentiate between secretory and osmotic diarrhea?
History and exam help with this question. If a child is thriving despite the diarrhea and drinks lots of juice, the likelihood of toddler's diarrhea (an osmotic diarrhea) is high. Weight loss, bloating, foul-smelling or fatty stools suggest maldigestion. This is a type of osmotic diarrhea, but calorie absorption is impaired because of incomplete digestion. Secretory diarrhea is typically not aggravated by or associated with the intake of any particular food.

The simplest objective way to confirm that diarrhea is osmotic or secretory is to stop all oral intake and observe what happens. Secretory diarrhea will persist when feeds are stopped, but osmotic diarrhea will cease. Obviously, this test can only be safely performed in the hospital with the patient on intravenous fluid replacement. However, variants of this can be performed at home when lactose intolerance or toddler's diarrhea is suspected. Strict elimination of dairy products from the diet or limiting the amount of fluids taken by a toddler should greatly reduce the stool volume in these cases.

Another objective test is to measure the stool osmotic gap. All stools are actually isosmotic--fecal osmolarity is always the same as other body fluids (about 280 mOsm/L). In secretory diarrhea, most of the osmolarity come from electrolytes- Na+, K+, and associated anions. Simply measuring stool sodium and potassium can therefore help you determine whether diarrhea is secretory or osmotic. The sum of sodium and potassium are multiplied by 2 to account for associated anions, and subtracted from 280:

Osmotic gap= 280- 2([Na+] +[K+])

This formula will yield a low number (<50) in secretory diarrhea, again because most of the stool osmolarity is the result of secreted electrolytes. In osmotic diarrhea, more of the fecal osmolarity is due to non-electrolytes, causing an "osmotic gap" of greater than 50 mOsm/L.

What tests should I order?
Not every child with diarrhea needs laboratory testing. When you suspect toddler's diarrhea in a thriving young child with large juice intake, no test is indicated, other than a trial of restricted clear liquid intake. Other historical and exam findings require appropriate investigation, as listed in Table 4.

Table 4: Laboratory investigation of chronic diarrhea
Clinical Information	Appropriate Test
Fever, bloody stools	Stool culture, complete blood count, consider radiologic investigation for inflammatory bowel disease, referral for colonoscopy
Foul-smelling, fatty stools, poor weight gain	Sweat chloride, fecal fat analysis, Sudan stain
Weight loss, variable diarrhea, bloating	Antibody testing for celiac disease (anti-endomysial antibodies, tissue transglutaminase antibody), consider referral for small-bowel biopsy
Thriving, watery stools, excessive liquid intake	None- trial of reduced liquid intake
Watery diarrhea and bloating, worse with dairy products	Trial of dairy restriction. Consider antibody testing for celiac disease.

How should I prevent or treat dehydration in acute diarrhea? One of the major advances in modern medicine has been the development of oral rehydration therapy (ORT) during the 1960s. ORT is simply a solution containing salts and glucose. This therapy takes advantage of the existence of a sodium-glucose cotransporter molecule, which continuously takes up sodium along with glucose, even in the presence of active intestinal secretion. Feeding children ORT solutions typically results in sufficient fluid absorption to treat or prevent dehydration. ORT solutions are listed in Table 5. Young children with diarrhea should always be given one of these fluids, not inappropriate low-electrolyte juices or carbonated beverages. Another important point is that early reinstitution of nutritional feedings results in more rapid resolution of diarrhea and better weight gain. There is no justification for the old practice of continuing clear liquids for several days before restarting feedings.

Table 5. Comparison of ORT Solutions with Common Beverages
Fluid	Glucose (g/dl)	Na (mEq/L)	K (mEq/L)	Base (HCO3 or citrate)
WHO solution	111	90	20	30
Pedialyte ®	139	45	20	30
Lytren ®	111	50	25	30
Rehydrolyte ®	139	75	20	35
Cola Beverage	~400 (varies)	2	0.1	13
Apple juice	~700	3	20	0

When are antibiotics required for bacterial and parasitic types of diarrhea?
Not all bacterial infections require antibiotic therapy. In many cases, as with Campylobacter, antibiotic therapy results in minimal or no shortening of the clinical course. Agents that are markedly invasive should always be treated, including Shigella and Enteroameba histolytica. Giardia and Vibrio cholerae also should always be treated, as treatment markedly shortens the course of disease. Salmonella treatment is recommended only for immunocompromised hosts, those with sickle cell disease, and for all infants, children with fever, or those with a positive blood culture. E.coli agents may be considered for therapy with severe or prolonged therapy. However, recent evidence indicates that treatment of the 0157:H7 serotype increase the risk of hemolytic uremic syndrome.

Case study:
A three year-old female is brought to you by her parents. She has been having 6 watery stools per day for the last 3 months. A trial of milk restriction from the diet resulted in no improvement. She has had no fever, there is no travel history, and no one else in the family has had diarrhea. Child has had no weight loss, does not seem ill, has had no complaints of abdominal pain, and has no history of mouth sores, rash, arthritis, or perianal disease. She does not attend daycare, and has not traveled outside the United States. Further questioning reveals that she has been taking no laxatives, and that none are in the medicine cabinet at home.

You advised the parents that their daughter's diarrhea was probably "toddler's diarrhea" caused by excessive intake of juices, and advised strictly limiting the volume of these. You ordered no other tests. The parents report back to you that the diarrhea is much less of a problem when they enforce this policy. At her next office visit, the little girl continues to follow the growth curve well, and is having only 2 soft stools per day. Child has been avoiding all dairy products and is being given large amounts of fruit juice every day to avoid dehydration. Evaluation of the growth chart shows that she is at the 75th percentile for both height and weight.

References:

• Chronic nonspecific diarrhea of childhood: pathophysiology and management. Kneepkens CM - Pediatr Clin North Am - 01 -Apr-1996; 43(2): 375-90
• Chronic diarrhea and malabsorption. Branski D - Pediatr Clin North Am - 01-Apr-1996; 43(2): 307-31
• Acute diarrhea in children. DeWitt TG - Pediatr Rev - 0 1 -Jul- 1989; 11 (1): 6-13
• "Feeding the gut": the scientific basis for continued enteral nutrition during acute diarrhea. Duggan C - J Pediatr - 0 1 -Dec- 1997; 13 1(6): 801-8

See related Provider Textbooks about Pediatrics.

See related Provider Topics Diarrhea, Digestive System, Gastrointestinal, Pediatrics or Symptoms and Manifestations.

See related Patient Textbooks about Pediatrics.

See related Patient Topics Diarrhea, Digestive System, Pediatrics or Symptoms and Manifestations.

All contents copyright © 1992-2004 the Author(s) and The University of Iowa. All rights reserved.

http://www.vh.org/pediatric/provider/pediatrics/diarrhea/index.html