Strange and Schafermeyer's Pediatric Emergency Medicine, Fourth Edition (Strange, Pediatric Emergency Medicine) 4th Ed.

CHAPTER

70

Vomiting, Diarrhea, and Gastroenteritis

Simon J. Lucio

HIGH-YIELD FACTS

• Vomiting and diarrhea due to acute infectious gastroenteritis remains one of the most common etiologies of childhood morbidity and mortality, especially in impoverished countries.

• Bilious vomiting in a neonate raises suspicion for bowel obstruction, especially malrotation, with or without a volvulus.

• Life-threatening causes of vomiting include bowel obstructions, increased intracranial pressure, diabetic ketoacidosis, and inborn errors of metabolism.

• Life-threatening causes of diarrhea include toxic megacolon and Escherichia coli 0157.

• Most dehydrated patients with gastroenteritis can be treated with oral rehydration solutions that now contain lower concentrations of glucose and sodium.

• Most cases of acute gastroenteritis are viral in nature and resolve with minimal intervention and without antibiotic therapy.

• Ondansetron can facilitate oral rehydration therapy (ORT) and decrease the need for IV therapy.

• Rotavirus is the most common cause of infectious diarrhea worldwide and the leading cause of infant death in the developing world.

• New vaccines against rotavirus are safe and effective and have decreased morbidity and mortality associated with rotavirus gastroenteritis.

• Campylobacter are the most common cause of bacterial gastroenteritis in developed countries and have been implicated as one of the cause of traveler’s diarrhea.

VOMITING

Vomiting is defined as the forceful expulsion of the contents of the stomach. Most acute infectious illnesses result in frequent vomiting of a short duration. In children, the most common cause of vomiting is acute gastroenteritis. The vomiting history should focus on the duration of the illness, frequency of the episodes, characteristic/color of the contents, associated abdominal pain, and any precipitating factors including trauma, recent illness, and medication. Protracted or intermittent vomiting can imply an underlying anatomic lesion. Pyloric stenosis should be considered in any infant age 2 to 6 weeks with vomiting. Bilious vomiting in an infant raises suspicion for bowel obstruction, especially malrotation, with or without a volvulus. Vomiting associated with persistent, severe, or localized abdominal pain suggests peritonitis. Bloody vomiting usually involves a lesion proximal to the ligament of Treitz. Vomiting accompanied by a headache or altered mental status raises the possibility increased intracranial pressure and may present with cranial suture splitting and/or bulging anterior fontanelle. Metabolic abnormalities due to inborn error of metabolism (occurring usually in infancy), diabetic ketoacidosis, uremia, and hyper or hyponatremia can also present with vomiting and altered mental status.14

Table 70-1 lists some life-threatening causes of vomiting.

TABLE 70-1

Life-Threatening Causes of Vomiting

Increased intracranial pressure

Bowel obstruction (malrotation, intussusception, incarcerated hernia, adhesions)

Inborn errors of metabolism

Diabetic ketoacidosis

Toxic ingestions

Reye syndrome

DIARRHEA

Diarrhea is defined as frequent loose or liquid bowel movements, three or more per day. The most common cause of diarrhea in children is acute infectious gastroenteritis. The history regarding diarrhea should focus on the characteristics of bowel movements (duration, frequency, and the presence of blood or mucus), travel history, state of hydration, and related signs and symptoms. Several general classifications of diarrhea exist. Secretory diarrhea is characterized by an increased secretion or decreased absorption of intestinal liquid and is often toxin mediated. Inflammatory diarrhea derives from damage to the intestinal mucosa. Osmotic diarrhea occurs when liquid is lost accompanying a high intestinal osmotic load. Increased intestinal motility can also cause diarrhea. Most acute gastrointestinal infections in the developed world are viral in etiology and result in frequent, watery stools. Blood or mucus in the stool raises the probability of a bacterial or inflammatory illness. Frank rectal bleeding suggests an anatomic lesion, such as an intussusception, Meckel diverticulum, or juvenile polyps. Protracted diarrhea suggests a malabsorption syndrome or inflammatory bowel disease. Patients with toxic megacolon may present with a history of diarrhea and altered mental status. Hirschsprung disease may be associated with a history of constipation, vomiting, and paradoxically, diarrhea caused by mucosal ulcerations in the proximal dilated segment. Physical examination may reveal palpable stool throughout the abdomen and an empty rectal vault. Profound diarrhea with accompanying rapid fluid and electrolyte losses can lead to shock and cause altered mental status. Cholera is the classic example, although, other viral causes such as rotavirus have also been implicated.17 Table 70-2 lists some life-threatening causes of diarrhea.

TABLE 70-2

Life-Threatening Causes of Diarrhea

Toxic megacolon (Hirschsprung disease, ulcerative colitis)

E. coli 0157 (hemolytic uremic syndrome)

Pseudomembranous enterocolitis (antibiotic-associated diarrhea)

GASTROENTERITIS

Acute infectious gastroenteritis remains one of the most common health problems throughout the world and accounts for approximately 1.8 million pediatric deaths per year. It remains a common cause of mortality in developing countries especially in younger, malnourished children. Gastroenteritis is also a major cause of morbidity in malnourished children. Inexpensive oral rehydration solutions have been instrumental in decreasing mortality from diarrheal illnesses throughout the world. In the United States, acute gastroenteritis is responsible for a substantial number of emergency department visits and hospitalizations, especially in children younger than 5 years, and may account for up to 300 deaths per year.3,4 Acute infectious gastroenteritis is the most common cause of vomiting and/or diarrhea and usually resolves with minimal intervention. Before establishing the diagnosis of gastroenteritis, other potentially life-threatening illnesses presenting with vomiting and/or diarrhea must be excluded by obtaining an in-depth history and performing a physical examination.

ETIOLOGY

In the United States, most cases of gastroenteritis are caused by viral infections that peak in the winter months. Rotavirus is the most common cause of infectious diarrhea worldwide and the leading cause of infant death in the developing world. Ninety-five percent of children in the United States have had rotavirus infection by the age of 5 years. Rotavirus accounts for 40% of all outpatient visits for diarrhea and 30% to 70% of hospital admissions for gastroenteritis. Transmission is by contact with contaminated environmental surfaces, close person-to-person contact, and only requires a low inoculation dose for infection. Prolonged asymptomatic viral shedding in the stool can also occur for up to 3 weeks. The diarrhea is often preceded by vomiting and is characteristically loose, watery, frequent, malodorous, and occasionally associated with mucous or blood. The diarrhea is both osmotic and secretory in nature and results in 8 to 20 watery stools per day. Fever may occur and the duration of symptoms typically last 3 to 7 days.18

Other viral agents implicated in acute infectious gastroenteritis include adenovirus serotypes 40 and 41, noroviruses (Norwalk-like viruses), calcivirus, and astrovirus. Noroviruses are responsible for a significant number of food-borne outbreaks. Infection usually last 12 to 48 hours and is characterized by fever, vomiting, myalgias, and malaise. Both rotavirus and adenovirus predominantly infect children younger than 3 years.68

In the developing world, bacterial infections account for a higher percentage of diarrheal illnesses compared to rates in industrialized nations. Enterotoxigenic bacteria include E. coli, Clostridium perfringens, cholera species, and Vibrio species whose toxin secretion causes diarrhea. Shigella species, Salmonella species, CampylobacterYersinia species, and Plesiomonas species are associated with inflammatory changes in the small and/or large bowel. Clostridium difficile, an antibiotic associated diarrhea, is also toxin mediated. Interestingly, a high percentage of infants are colonized with C. difficile, yet rarely experience disease. Noninvasive parasites implicated in diarrheal illnesses, include Giardia species and Cryptosporidium species. Giardia is prevalent in children attending day care and causes both acute and chronic diarrhea. The minimum infective dose is low at 10 to 100 cysts. Left untreated, infected individuals can shed cysts for months. Entamoeba histolytica is an invasive parasitic cause of diarrhea commonly found in the tropics during the rainy season.68

PATHOPHYSIOLOGY

In acute infectious gastroenteritis, diarrhea occurs when intestinal output exceeds the ability of the gastrointestinal tract to reabsorb liquid. Viruses directly damage the small intestinal villi causing carbohydrate malabsorption and watery osmotic diarrhea production. Rotavirus may also secrete an enterotoxin that contributes to secretory diarrhea. Bacteria produce diarrhea by a variety of mechanisms.13

Enterotoxigenic E. coli is the most common cause of traveler’s diarrhea and the most common cause of bacterial diarrhea in children worldwide; it is uncommon in the United States. It infects the small intestine causing noninvasive watery diarrhea via two major toxins. Enteropathogenic E. coli are an important cause of diarrhea in infants in developing countries, especially with diarrhea lasting more than 2 weeks; the mechanism by which diarrhea occurs is not known.

Enterohemorrhagic E. coli 0157 causes an invasive hemorrhagic colitis. The source of infection is cattle or sheep. It is acquired by ingestion of undercooked meat, unpasteurized milk, or transmission from other infected individuals. The illness begins with nonbloody watery stools and progresses to grossly bloody diarrhea associated with severe abdominal pain. Hemolytic uremic syndrome occurs in 5% to 10% of cases characterized by thrombocytopenia, hemolytic anemia, and oliguria.

Shigella infection is associated with rapid onset of fever and large voluminous watery stools. It can cause invasive diarrhea after exposure to as little as 10 organisms. Colonization of the colonic epithelium causes intestinal ulcerations, neutrophil infiltration, and resultant bloody diarrhea, except in infants where the diarrhea can be nonbloody. It is commonly spread via person-to-person contact. The diarrheal illness can be associated with altered mental status but usually is not life-threatening. Shigella secretes various toxins, including Shiga toxin, implicated in hemolytic uremic syndrome. Shigella infection is also associated with febrile seizures in children.

Salmonella enteritidis is a common cause of self-limited, noninvasive diarrhea. It is found commonly in contaminated food (eggs, meat, poultry), other farm animals, and pet turtles. Infants younger than 1 year, patients with sickle cell disease, and immunocompromised patients are at risk for bacteremia from S. enteriditis. Salmonella typhi and paratyphi infect only humans and are capable of causing serious blood-borne disease, especially in infants and children, and remain a common cause of mortality in many parts of the world. Campylobacter are the most common cause of bacterial gastroenteritis in developed countries and have been implicated as a cause of traveler’s diarrhea. Transmission occurs via consumption of contaminated food or water, person-to-person contact, and pet-to-person contact. Infection causes inflammatory enteritis, abdominal pain, a flu-like syndrome, and diarrhea that is profuse, mucousy, and bloody. Campylobacter is also associated with Guillain–Barre syndrome.58

DIAGNOSTIC EVALUATION

image PHYSICAL ASSESSMENT

The physical examination of the patient with vomiting and/or diarrhea should focus on excluding life-threatening illnesses and determining if the diagnosis is indeed gastroenteritis. Assessment of the patient’s mental status is a key aspect of the physical examination. Lethargy or irritability may indicate severe dehydration or a significant metabolic disturbance or anatomic lesion. Once the diagnosis of gastroenteritis is assured, assessment of the patient’s hydration status should be performed (Table 70-3). Children with significant vomiting and diarrhea will have fluid and electrolyte deficits. Total body water loss is calculated as a percentage of body weight: 3% to 5% loss is considered mild, 5% to 10% moderate, and greater than 10% severe. The percent of dehydration is often an estimated measure, given that the patient’s baseline weight may not be known. The extent of illness in the patient depends not only on the fluid deficit, but the rate at which it has occurred. Fluid losses occurring slowly are compensated by water shifting from intracellular and interstitial spaces into the intravascular space, protecting systemic perfusion. Fulminant losses from severe diarrhea are poorly compensated, especially in infants, and can result in hypovolemic shock and death. The degree of dehydration is often difficult to assess in younger infants. A variety of methods exist for estimating the extent of dehydration. Current emphasis is focused at simplifying the hydration assessment process; mild and moderate dehydration can be grouped together. Key findings indicating significant dehydration include delayed capillary refill, abnormal skin turgor, and an abnormal respiratory pattern. Other important findings include tachycardia, dry mucus membranes, and the absence of tears.9 The importance of assessing mental status cannot be overstated. Guidelines from the World Health Organization (WHO) and UNICEF for managing diarrhea in children are available on the Internet.3,4

TABLE 70-3

Assessment of Dehydration

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image DIAGNOSTIC STUDIES

Most children with gastroenteritis do not require laboratory studies commonly ordered in the emergency department, as they rarely aid in the evaluation and management. When moderate or severe dehydration is present, it may be reasonable to obtain serum electrolytes; however, the patient’s hydration status can usually be ascertained from the physical examination. Most patients with significant diarrhea will have low serum bicarbonate. Hypoglycemia can accompany significant dehydration or altered mental status and warrants a bedside glucose evaluation. Stool sample for culture and ova/parasites should be considered in patients with bloody diarrhea or protracted diarrhea. Fecal leukocytes found in the stool may suggest colitis and the presence of an enteroinvasive infection, but testing has poor sensitivity and cannot discern a definite etiology. Blood cultures should be obtained in those who are at risk for bacteremia: infants and children younger than 1 year, patients with sickle cell disease, and immunocompromised patients in whom salmonella is suspected. Rotavirus antigen can be detected in the stool via enzyme immunoassay and latex agglutination but has a high false-negative rate. CBC with platelet count, electrolytes, BUN, and creatinine should be evaluated if the patient has E.coli 0157 or is suspected of having hemolytic uremic syndrome.1,3,58

image TREATMENT

Oral Rehydration Therapy ORT is an effective treatment for the vast majority of patients with gastroenteritis-related dehydration. ORT is credited with saving millions of lives around the world. In environments where intravenous therapy is available, ORT use has been reportedly underutilized.10 The coupled transport of sodium and glucose molecules at the intestinal brush border accompanied by free water transport is the mechanism of efficacy for ORT. A variety of oral hydration solutions (ORS) are available. Recent guidelines from the WHO and UNICEF recommend reduced concentrations of sodium (65–75 mEq/L) and glucose (75 mmol/L) in ORS. The osmolarity reduction hastens the effect of hypertonicity on net fluid absorption and shortens the duration of diarrhea and need for intravenous fluids. In most cases, rehydration can be accomplished without the risk of causing hypo- or hypernatremia.1116

Treatment for infants and children with minimal dehydration is directed at maintaining nutrition and preventing dehydration. Rehydration can be achieved by increasing fluid intake or by administering ORS at a volume of 10 mL/kg for each stool and/or 2 mL/kg for each emesis. Continued feeding or increased breastfeeding during, and increased feeding after the diarrheal episode is recommended.4 Diet should generally not be restricted. If vomiting is present, consider limiting intake to clear liquids (Pedialyte, Ricelyte, Rehydralyte, Gatorade) and bland items (toast, crackers, rice, clear soup) until the vomiting has ceased for several hours, and then gradually advancing to a normal diet.

Patients with mild-to-moderate dehydration should receive 50 to 100 mL/kg of ORS over 2 to 4 hours with ongoing losses also replaced. Nasogastric administration of ORS is safe, effective, and beneficial in patients in whom intravenous access is difficult, or in infants who have difficulty swallowing.17 Moderately dehydrated patients who require intravenous rehydration can be rehydrated over several hours in the emergency department.18

Patients in shock or with severe dehydration require intravenous therapy. An initial bolus of 20 mL/kg of 0.9 NS or lactated Ringer’s is rapidly administered and can be repeated until adequate perfusion is restored. Once perfusion is restored, hydration can be continued intravenously or by instituting ORT. Intravenous therapy involves replacing the estimated volume deficit along with maintenance fluid requirements.18 Intravenous rehydration is discussed further in Section XIV, “Fluid, Electrolyte and, Acid Base Abnormalities.”

image ADJUNCTIVE THERAPY

Persistent vomiting can limit or delay oral rehydration. Studies have shown that ondansetron facilitates ORT in children with persistent vomiting and decreases the need for intravenous salvage therapy. The dose for ondansetron is 0.15 mg/kg but a general guideline for infants and children is: 2 mg for 8 to 15 kg, 4 mg for 15 to 30 kg, and 6 to 8 mg for more than 30 kg.1925 Zinc deficiency is widespread in the developing world. Numerous studies have shown that zinc supplementation reduces the severity and duration of diarrhea in children younger than 5 years and reduces the incidence of diarrhea in the proceeding 2 months. The WHO recommends zinc supplementation (10–20 mg/d for 10–14 days) in children with diarrhea.4,26 Maintaining the nutritional status of children with diarrhea is vitally important, especially in those who are malnourished. Breastfeeding and/or an age-appropriate diet should resume as soon as the patient can tolerate feeding without vomiting. Insufficient evidence exists to support withholding lactose-containing formulas in patients with acute diarrhea. Liquids containing high sugar loads, such as colas and apple juice are best avoided because they can increase the intestinal osmotic load and worsen diarrhea.3,4 Probiotics have been used in the treatment of diarrheal illness for several years, yet studies have shown only limited benefit for mild, self-resolving causes of diarrhea. Some evidence support the use of Lactobacillus GG in addition to traditional therapy for antibiotic associated C difficile diarrhea.27 Antibiotic therapy or stool culture is not indicated in the majority of cases of diarrheal illness. Patients can have bloody diarrhea derived from underlying viral illness, such as rotavirus, or a self-limiting bacterial illness such as nontyphoidal salmonella. Stool for culture should be considered in children younger than 1 year who are febrile and toxic-appearing or those with persistent bloody diarrhea. Culture and sensitivity testing will direct antibiotic therapy. (Tables 70-3 and 70-4)

TABLE 70-4

Treatment of Common Gastrointestinal Infections

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Antidiarrheal agents, including pectin and kaolin, have no therapeutic benefit. Abdominal cramping can be exacerbated in children taking Diphenoxylate (Lomotil), especially in those infected with Shigella.

PREVENTION

Prevention of gastroenteritis fundamentally depends on improving hygiene practices. Attention to hand-washing and improved handling of meat, poultry, and egg products has had a profound impact in the industrialized world. In the developing world, many barriers exist that impede hygiene practice, including lack of access to portable water; inability to boil water, and inadequate sanitation measures. Access to latrines is an important public health goal in developing nations where plumbing is nonexistent.28

Vaccines have been or are being developed for several of the most common causes of gastroenteritis. A vaccine licensed in 1998 for rotavirus was withdrawn within a year because it was associated with an increased risk of intussusception. Since then, two vaccines against rotavirus have been developed, and are currently in use.2931 Introduced in the United States in 2006, these new vaccines have significantly decreased morbidity and mortality associated with rotavirus gastroenteritis. A reduction in hospitalizations, emergency department, and outpatient visits for diarrhea has been reported compared with the prevaccine era.3235

Salmonella typhi, prevalent in Asia, is capable of causing fatal disease especially in young children. Two vaccines licensed for children older than 2 years are now available (one oral and the other injectable) and have shown to be safe and efficacious.36 Oral cholera vaccines have been developed that are effective in reducing incidence and severity of disease. Vaccines against ShigellaCampylobacter, and enterotoxigenic E. coli are in various stages of development.37

ACKNOWLEDGMENT

The author would like to thank Dr. William R. Ahrens.

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