Stephen B. Freedman
EPIDEMIOLOGY
Acute viral gastroenteritis is the most common cause of vomiting and diarrhea in children. Clinical diagnosis requires the presence of diarrhea.
Acute vomiting is usually caused by a self-limited viral illness. Nonetheless, more serious diagnoses must be considered.
Acute gastroenteritis is defined by the presence of three or more diarrheal stools in a 24-hour period. An increase in stooling frequency and/or change in consistency in infants is consistent with diarrhea. Recognition is important, as young infants can develop gastroenteritis and, given their small size and limited fluid reserves, are at high risk for developing dehydration and hypoglycemia.
Most enteric infections are self-limited, but excessive water and electrolyte loss resulting in clinical dehydration may occur in 10% and is life threatening in 1%.
Pathogenic viruses, bacteria, or parasites may be isolated from nearly 50% of children with diarrhea. Viral infection is the most common, but bacterial pathogens are isolated in 1% to 4% of cases.
The major bacterial enteropathogens in the United States are Campylobacter jejuni, Shigella species, Salmonella species, Yersinia enterocolitica, Clostridium difficile, and Escherichia coli. Escherichia colihas three pathogenic varieties, including enterohemorrhagic (serotype O157:H7), which is associated with hemolytic-uremic syndrome.
Giardia lamblia is a parasitic infection and a common cause of diarrhea in infants and young children in day care centers.
PATHOPHYSIOLOGY
Viral, parasitic, and bacterial pathogens cause disease by tissue invasion and alteration of intestinal absorption of water and electrolytes.
Some bacterial pathogens such as E. coli, Vibrio chol-erae, and Shigella cause diarrhea through production of enterotoxins and cytotoxins and invasion of the mucosal absorptive surface.
The small bowel absorbs the vast majority of water in the gastrointestinal tract. Pathogens that interfere with water absorption in this area tend to produce voluminous diarrhea. By contrast, disease processes that affect the colon, such as dysentery, produce frequent, small-volume, often bloody stools.
Fasting, which frequently occurs with gastroenteritis, worsens the capacity of the bowel to absorb fluids. Continued feeding not only slows progression of dehydration by increasing the volume of fluid available to the intravascular space, but the presence of nutrients in the bowel lumen promotes mucosal recovery and improves fluid absorption.
CLINICAL FEATURES
Evaluation of a child’s state of hydration is most important. If possible, it is best to determine the degree of fluid loss by comparing the child’s current weight to a recent previous weight. A history of normal fluid intake and normal urine output drastically reduce the likelihood of significant dehydration.
When objective measurements such as pre- and post-illness weights are not available, the state of hydration can be assessed by physical examination (Table 75-1).
TABLE 75-1 Clinical Signs in Dehydration
DIAGNOSIS AND DIFFERENTIAL
History and physical examination are the most important tools in diagnosis. Most children with acute vomiting and diarrhea have self-limited viral illness.
Specific clinical findings, such as bilious or bloody vomitus, hematochezia, or abdominal pain, should trigger concerns of a disease process other than simple viral gastroenteritis (Table 75-2), or a potential complication of gastroenteritis.
Check a bedside glucose on all patients with vomiting or diarrhea and altered mental status and in infants and toddlers with protracted symptoms, which may cause hypoglycemia.
Serum electrolytes are usually not necessary because dehydration caused by diarrhea is usually isotonic and laboratory parameters are subject to inaccuracy. They should, however, be performed in moderately dehydrated children whose history and physical examination findings are inconsistent with acute gastroenteritis, severely dehydrated children, and all children requiring intravenous rehydration, or those with potential hyper- or hyponatremia (see Chapter 83).
Obtain stool cultures in children with the following high-risk features: >10 stools in the previous 24 hours, travel to high-risk area, fever, older age, and blood or mucus in the stool. In the context of an outbreak of hemolytic uremic syndrome or a positive blood culture for E. coli O157:H7, further testing to rule out evidence of renal failure, thrombocytopenia, and hemolytic anemia should be performed.
Special attention should be given to those children who have chronic debilitating illnesses, high-risk social situations, or malnutrition, since they are at particular risk for rapid decompensation.
Bilious vomiting should always raise suspicion for an obstructive lesion distal to the ampulla of Vater.
The differential diagnosis of vomiting is age specific, and serious diagnoses that need to be considered include metabolic (eg, inborn errors of metabolism, congenital adrenal hyperplasia, diabetes mellitus), neurologic (eg, intracranial hemorrhage, hydrocephalus, cerebral edema), surgical/gastrointestinal (eg, esophageal or intestinal stenosis/atresia, pyloric stenosis, malrotation ± volvulus, incarcerated hernia, Hirschsprung disease, intussusception, foreign body, Meckel’s diverticulum), renal (eg, urinary tract infection, obstructive uropathy, renal insufficiency), infectious (eg, gastroenteritis, meningitis, sepsis, pneumonia), and other disease states (eg, gastroesophageal reflux, necrotizing enterocolitis, milk allergy, appendicitis, pregnancy, cyclic vomiting syndrome).
The differential diagnosis of diarrhea includes infection (eg, viral, bacterial, parasitic), dietary disturbances (eg, food allergy, starvation stools), anatomic abnormalities (eg, Hirschsprung disease, partial obstruction, appendicitis), inflammatory bowel disease, malabsorptive or secretory diseases (eg, cystic fibrosis, celiac disease), systemic diseases (eg, immunodeficiency, endocrinopathy), and other causes (eg, antibiotic associated diarrhea, secondary lactase deficiency).
Causes of diarrhea that may result in significant morbidity include infection (eg, Salmonella gastroenteritis with bacteremia, Shigella, C. difficile), anatomic abnormalities (eg, intussusception, toxic megaco-lon, appendicitis), inflammatory bowel disease, and hemolytic uremic syndrome. Appendicitis may cause diarrhea, particularly after the appendix has perforated.
TABLE 75-2 Etiologies of Vomiting That May result in Significant Morbidity, categorized by age
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Therapy is determined by the severity of dehydration:
Mild: Continue with the child’s preferred, usual, and age-appropriate diet.
Moderate: Administer oral rehydration therapy. Aim for 25 to 50 mL/kg over 1 to 2 hours. Reassess in 1 hour. If sufficient intake and clinically less dehydrated, then continue age-appropriate diet at home. If no improvement, options include continuing oral rehydration for 1 additional hour, nasogastric rehydration, or intravenous rehydration.
Severe: Treat emergently as indicated for hypovo-lemic shock with isotonic crystalloids administered as 20 mL/kg boluses and repeated until clinical improvement is noted (see Chapter 83).
If vomiting is the prominent symptom:
Treat with oral rehydration with a glucose-electrolyte oral rehydration solution (ORS) using frequent, small volumes. Aim for 1 ounce (30 mL) of ORS/kg/h. Avoid other beverages (eg, tea, juice, sports drinks), which are deficient in sodium and provide excess sugar, resulting in amplified losses.
Consider intravenous rehydration with isotonic crystalloid administered via IV, IO, or NG routes in children with severe dehydration, with hemodynamic compromise, or when altered mental status precludes safe oral fluid administration.
A single dose of ondansetron, a 5-hydroxytryptamine receptor antagonist, may be used as an adjunct to ORT in children with persistent vomiting at a dose of 0.15 mg/kg PO or 0.1 mg/kg IV.
Dopamine receptor antagonists should not be used to treat vomiting in children because of the potential for serious side effects and lack of evidence of efficacy.
If diarrhea is the prominent symptom:
Children with mild diarrhea who are not dehydrated should continue routine feedings.
Children with moderate to severe dehydration should first receive adequate rehydration before resuming routine feedings. Food should be reinstated after the rehydration phase is completed and never delayed more than 4 hours. There is no need to dilute formula, or recommendation of a lactose-free milk or the bananas, rice, applesauce, and toast (BRAT) diet.
Dietary recommendations include a diet high in complex carbohydrates, lean meats, vegetables, fruits, and yogurt. Fatty foods and foods high in simple sugars should be avoided.
Antidiarrheal medications are not recommended in children due to safety concerns and a lack of effectiveness data. Antimotility agents, which can reduce diarrhea, have potential serious adverse effects (eg, lethargy, paralytic ileus, death), and are contraindicated in children.
Bismuth, which can reduce the severity of diarrhea, can cause salicylate poisoning, and is not recommended in children <12 years of age.
Antibiotics are unnecessary for the vast majority of children with acute gastroenteritis and are only indicated for specific pathogens or clinical settings (Table 75-3).
Admit all infants and children who appear toxic or have high-risk social situations, significant dehydration, intractable vomiting, altered mental status, an inability to drink, or laboratory evidence of hemolytic anemia, thrombocytopenia, or elevated creatinine levels.
Families of discharged patients should be given instructions to return or seek care with their primary physician if the child has increased emesis, bilious vomiting, or signs of dehydration such as decreased activity level, or urination.
TABLE 75-3 Clinical Features and Treatment of Etiologic Agents of Bacterial Gastroenteritis
For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 123, “Vomiting, Diarrhea, and Dehydration in Children,” by Stephen Freedman and Jennifer Thull-Freedman.