Clinical Consult: Diarrhea in children

Diarrhea in children

Diarrhea is a very common problem. Almost every child has at least one episode of infectious viral gastroenteritis in his or her life (like rotavirus or norovirus) marked by fever, vomiting and watery diarrhea. While most diarrhea is self-limiting, it is important to recognize when testing is needed, when medical evaluation and fluid support may be helpful, and when to suspect a chronic problem that requires specialist testing and endoscopy to find the cause and direct specific treatments, be they drugs or special diets and supplements.

Key questions for the medical history

There are some key questions that can best help clinicians figure out what is wrong and what might be needed to help:

  • Are we sure this is diarrhea? Diarrhea is defined as increased liquidity of the stool and the passage of excessive amounts of stool. The traditional definitions of diarrhea are stool output in excess of ~200 grams/day in older children and 10 grams/kilogram/day in an infant or toddler. When there is diarrhea, generally stools are occurring at least three times per day. For patients with small volume but liquid stools, especially if there is soiling, it becomes important to exclude overflow diarrhea (see below) and in older children to verify if indeed liquid stools are occurring.
  • Is the stool bloody? This is important because it could indicate that there is significant inflammation in the small intestine or colon. Generally speaking, bloody diarrhea is obvious and does not need to be confirmed with a guaiac test. Confirmation is necessary when the color is not bright red, or the history or physical exam do not fit with the stool description. When diarrhea onset is recent, usually the cause is a bacterial infection. Other important causes of bloody diarrhea include allergy in infants and when there is chronic diarrhea, inflammatory bowel disease. Children who appear ill (see below) should be referred urgently to an emergency department for surgical evaluation, appropriate laboratory testing and fluid/electrolyte support.
  • Is there a fever? In many circumstances, knowing that there is a fever is reassuring since the cause is likely infectious, most infections are viruses and most viral infections are self-limited. However, in infants, children with indwelling intravenous catheters and patients with compromised immune systems, fever could indicate a related or unrelated life-threatening infectious illness and should be promptly evaluated and treated.
  • Could this be overflow diarrhea? It can be counterintuitive that significant constipation could cause diarrhea. And it is easy for clinicians to forget about this important concept: chronic rectosigmoid fecal impaction can cause diarrhea because of newly formed stool “leaking” around the firm impaction. The treatment is disimpaction with oral, and sometimes rectal, softeners and stimulants.
  • How long has the diarrhea lasted? Chronic diarrhea is generally considered lasting longer than 14 days. Diarrheal conditions that resolve in fewer than 14 days are generally caused by self-limited infections. Most acute diarrhea resolves within a week. There is no need for alarm if recovery is somewhat delayed, since the intestinal lining may require several days to regenerate full function after a significant infectious enteritis. Chronic diarrhea ought to be taken seriously and should be evaluated in clinic with full history and physical, along with directed laboratory testing as appropriate.
  • Does diarrhea continue throughout the night? This is typically considered a sign that there is excessive secretion unrelated to eating. Most commonly, this indicates ongoing inflammation causing fluid secretion and/or inflammatory exudation. When this is chronic, further evaluation is necessary.
  • Are there signs of systemic illness? It is almost common sense to worry when children appear ill. Particularly dangerous conditions can manifest as diarrhea with worrisome systemic features such as severe abdominal pain, tachycardia, lethargy and pale skin color. In the appropriate clinical context, potential culprits could include pseudoappendicitis caused by Yersinia entercolitica, Hirschsprung’s enterocolitis (Hirschsprung’s disease), intussusception, pseudomembranous colitis caused by Clostridium difficile, appendicitis and hemolytic uremic syndrome.
  • Is there a problem with growth? Most clinically significant chronic diarrheas requiring treatment manifest as a reduced weight gain and height gain. We can be much less worried about a serious problem when weight and height gain are maintained.
  • What kind of diet? Beyond lactose intolerance, a good dietary history can be nearly diagnostic. For example, “juicerrhea” arises from excess intake of apple juice and other sorbitol-rich fruit juices. Less obvious are diets that are enriched with simple and complex refined carbohydrates (crackers, cookies, chips, raisins, fruit roll-ups, yogurt pops), which can be associated with functional diarrhea or “toddler’s” diarrhea. If diarrhea emerged exactly at the time table food was introduced, this can uncommonly indicate a problem with particular sugar and starch digestion.
  • Is the patient a young infant? Infants younger than 6 months of age are more likely to get dangerously dehydrated quickly. We suggest evaluating babies for signs of hypovolemia within a day of developing diarrhea, especially when there is accompanying vomiting.
  • Recently or currently on antibiotics? Antibiotics are a major risk factor for C. difficile infection, although it is important to recognize that infections can also occur without recent antibiotic exposure. Some antibiotics themselves cause diarrhea, like clavulanic acid, erythromycin and azithromycin.
  • Recurrent serious or unusual infections? Some chronic diarrheas are associated with immunodeficiency syndromes, like immunodysregulation, polyendocrinopathy, enteropathy and x-linked (IPEX) syndrome.

Red flags on physical examination

The physical exam can help guide diagnosis of diarrheal conditions, assess for malnourishment and of course hydration status. Some particular features to watch for include:

Diarrhea physical exam

  • Muscle wasting: Look at the temples and the buttocks. This is classically described in celiac disease, but any significant malabsorption can cause lean body mass deficits and therefore indicate a chronic condition affecting nutrient absorption.
  • Rashes: Severe eczema is associated with IPEX, while particular diaper, perioral and acral rashes can indicate vitamin and mineral deficiencies, like zinc. Nutritional rashes usually indicate that there is a chronic problem with absorption or excess loss. Very restricted diets can also lead to nutritional rashes, such as those associated with vitamin C deficiency.
  • Pallor: True pallor — best assessed by examining the conjunctiva, nail beds, or gums — could suggest anemia. Iron-deficiency anemia is the most common anemia associated with chronic diarrhea and indicates iron loss in the stool from bleeding and/or poor absorption from the upper intestine. In either case, iron deficiency despite an adequate diet suggests a nontrivial chronic diarrheal disorder.
  • Tenderness: Tenderness that is more than mild or moderate and which has any reproducible focality should prompt concern for a surgical, biliary or pancreatic process. Especially in young children and infants, such a finding calls for prompt emergency room evaluation.

Helpful laboratory tests

Laboratory testing is used to determine an infectious cause for diarrhea, assess for electrolyte disorders and look for particular underlying causes or evidence of malabsorption. Some key points:

  • When DON’T you need laboratory testing for a child with diarrhea? Laboratory testing is almost always unnecessary for acute diarrhea in a well-hydrated older infant and child. Stool and viral cultures or other assays are usually superfluous for healthy children at home with acute non-bloody diarrhea.
  • What laboratory testing SHOULD one do for diarrhea? For patients with acute bloody diarrhea, bacterial stool culturing should be performed, including evaluation for C. difficile infection. Diarrhea in patients on or recently off systemic antibiotics ought to be tested for C. difficile. Any patient with chronic diarrhea who is eating gluten-containing food (food with wheat, barley or rye) should be checked for celiac disease with a total IgA and IgA anti-tissue transglutaminase antibody. For chronic diarrhea with features of malabsorption, laboratory testing is critical and generally involves evaluation of serum proteins, vitamins, inflammatory markers, electrolytes and transaminases, as well as stool testing for evidence of malabsorption.

Treating diarrhea in children

Diarrhea treatment is generally supportive, meaning that we give appropriate fluids and nourishment without specific therapy directed at an underlying cause. This is nearly always all that is necessary for acute diarrheas.

Treating diarrhea in children

  • What you DON’T need to do: Limited diets such as the BRAT diet (bread, rice, apples, toast) do not help and could worsen diarrhea depending on how much “apple” is given. It’s better to maintain a normal, nutritionally adequate diet with the proper balance of fat, protein and carbohydrate.
  • Hydration: Oral rehydration solutions such as Pedialyte are standard for rehydration and maintaining hydration in young children with diarrhea. Older children should drink plenty of water along with a regular diet.
  • Avoidance of lactose: Often this is not necessary. However, if a particular patient develops diarrhea on lactose-containing foods, it is prudent to limit lactose for two to four weeks. Particular guidance is important, because lactose avoidance is often confused with milk protein avoidance. Advice from a dietitian can be helpful.
  • Probiotics: There are many probiotic products on the market. While studies have demonstrated that probiotics can help reduce length of illness in acute diarrhea, the benefit is modest and when compared to the burdens of cost and planning around administration, the ultimate value is not obvious. Nevertheless, they are generally safe and represent a treatment parents can use.
  • Loperamide: Loperamide is an anti-diarrheal medication that slows motility and likely decreases secretion. This medication is appropriate for some conditions like short bowel syndrome or traveler’s diarrhea. In most instances, however, it is unnecessary and more likely to cause complications.
  • FODMAP diet: The fermentable oligo-, di- and monosaccarides and polyols (FODMAP) diet can be helpful for children with functional diarrhea, such as irritable bowel syndrome, or functional diarrhea in younger children. The idea is to avoid substances that can ferment into molecules that can cause osmotic diarrhea or induce secretion.When considering the FODMAP diet, enlist the formal help of a dietitian, as it can be difficult for families to avoid foods containing such substances without assistance.

When to refer to a pediatric gastroenterologist

Gastroenterologists can be most helpful in diagnosing and managing patients with chronic diarrhea. For children who are growing normally and more likely have functional diarrhea or irritable bowel syndrome, initial primary care management can be best. Often, there are questions about the need for a colonoscopy,  endoscopy, breath testing, or specialized laboratory testing. In these cases, it is appropriate to refer to a gastroenterologist who can help the family or patient understand if and when these procedures or tests are needed.

When there is concern for the following:

  • inflammatory bowel disease
  • celiac disease
  • immunodeficiency syndromes
  • pancreatic insufficiency
  • malabsorptive or clinically significant chronic diarrhea
  • allergic gastroenteritis
  • debilitating functional pain with or without diarrhea

it makes sense to partner with a gastroenterologist so that specialized testing and multidisciplinary evaluation can be performed to confirm diagnoses and start disease-directed treatment.

Daniel Kamin pediatric gastroenterologist


Daniel S. Kamin, MD, is the director of inpatient consultation services in Boston Children’s Hospital’s Division of Gastroenterology, Hepatology and Nutrition.



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