Diarrhea is defined as softening in the consistency of the stool (increased water content of the stool), usually with increase in number of stools. Any deviation of the usual pattern of an individual should be concerning, regardless of the actual number of stools or water content.

• Major causes of diarrhea include viral and bacterial infections, dietary disturbances, and antibiotic administration (e.g., pseudomembranous colitis).

• Most of the disorders (especially viral gastroenteritis) are usually mild; however, any cause of diarrhea can produce a fatality secondary to dehydration.

• Life-threatening causes of diarrhea include: intussusception, hemolytic-uremic syndrome, pseudomembranous colitis, salmonella gastroenteritis (neonate only), Hirshsprung's disease, and inflammatory bowel disease.

• Important historical questions to ask include: is there a history of gastrointestinal surgery, inflammatory bowel disease, immunosuppression, recent hospitalization, recent travel (especially to a foreign country), or institutionalization (these can all lead to an increased susceptibility to infection)?

• Detailed questions should cover the number and size of stools, the frequency of emesis, the amount of fluid taken orally, the duration of illness, and whether visible blood is present in the stools.

• A decrease in the frequency or volume of urination (or the number of diaper changes in an infant) suggests an inadequate output, indicating the development of dehydration.

• The onset of symptoms and the characteristics of bowel movements are important. Pay particular attention to factors that increase (time, diet, etc.) or decrease (dietary elimination, withdrawal of a medication, etc.) the diarrhea.

• It is always important to weigh the child carefully (undressed) and compare the weight with previous weights recorded in the chart. If a child returns a day or two later, there is a tendency among ancillary personnel to record the previous day's weight instead of a new weight. This is a risky practice and may lead to a false reassurance about the child's condition. Don't permit this to occur.

• In assessing the degree of a child's dehydration, look at pulse, blood pressure, skin turgor, and mucous membranes. Note that the child who has hypernatremic dehydration can be an exception to the usual guidelines.

• Not all children with infectious enteritis have a fever, although an elevated temperature points in this direction. The absence of fever, especially in the presence of bloody stools, should alert the physician to the possibility of a noninfectious disease, such as intussusception or hemolytic-uremic syndrome.

• Hematochezia (bloody stools) with or without fever also may be secondary to an infectious enteritis or pseudomembranous colitis.

• The abdominal examination is important. The finding of a mass may indicate intussusception. Any guarding, rebound tenderness, or other peritoneal signs should alert the physician to a possible surgical abdomen. With overflow diarrhea secondary to chronic constipation, the rectal ampulla contains a large amount of hard stool. If you do a rectal exam, always do a guaiac test.

Laboratory Data (some or all of these may be indicated).

• Urine specific gravity is a good indicator of hydration status.

• Methylene blue smears for stool polymorphonuclear cells (these are commonly seen in bacterial gastroenteritis).

• Stool cultures (may need to repeat these several times) and gram stain.

• Examination of stools for ova and parasites.

• Assay for Clostridium. difficile toxin.

• Rotavirus culture (highly contagious; seen in day care settings).

• Guaiac test.

• CBC.

• Electrolytes.

Management

• Correct fluid deficits.

• Treat the specific condition.

• Hospitalization is required if the following situations occur: dehydration (moderate to severe), intractable vomiting, young age (especially under 2 to 3 months old), underlying disease, systemic toxicity, or disrupted social/physical environment.

• Be especially careful in evaluating the very young infant with a constellation of fever, vomiting, and diarrhea.

• Patients with severe abdominal pain associated with bloody stools require immediate evaluation and surgical consultation.

• Here is one practical approach to treatment of diarrhea in a child:

• Bowel rest, in the form of clear liquids. This should not exceed 24 hours.

• Withdrawal of milk products and milk-based formula (recent literature suggests that this may not be critical).

• Give the child as regular a diet as possible as soon as possible.

Patients whose clinical status is stable can usually be followed at home. Use a standard rehydration solution such as Lytren or Pedialyte. Many if not most practitioners still withdraw milk and milk-based formulas (lactose) from the child's diet until the diarrhea abates. For formula-dependent infants, most practitioners substitute a lactose-free formula such as Isomil, Prosobee, or Nursoy. For older children, a regular diet means just that: regular (for age). Note that the so-called BRAT diet (bananas, rice cereal, applesauce, toast) is markedly deficient in protein and is essentially a prescription for kwashiorkor if it is continued for any length of time. If you choose to use this antiquated approach, make sure that there is an end-point of a few days.

The patient should return if:

• The diarrhea or vomiting is increasing in frequency or amount.

• The diarrhea does not improve after 24 hours of clear liquids or resolve entirely after 3-4 days.

• Vomiting continues for more than 24 hours.

• The stool has blood, or the vomited material contains blood or turns green.

• Signs of dehydration develop, including decreased urination, less moisture in diapers, dry mouth, no tears, weight loss, lethargy, or irritability.