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 duration of the illness, frequency of 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 nonbilious 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 emesis usually involves a lesion proximal to the ligament of Treitz. Vomiting accompanied by a headache or altered mental status raises the possibility of 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.^1–4

Table 71-1 lists some life-threatening causes of vomiting.

Diarrhea is defined as frequent episodes (three or more per day) of loose or liquid bowel movements. 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.^1–8 Table 71-2 lists some life-threatening causes of diarrhea.

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.^3–7 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.

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.^1–9

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 lasts 12 to 48 hours and is characterized by fever, vomiting, myalgias, and malaise. Both rotavirus and adenovirus predominantly infect children younger than 3 years.^6,8,9

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, Campylobacter, Yersinia 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 daycare 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.^6–9

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.^1–3

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 O157 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 non-bloody 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 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 non-bloody. 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), 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. enteritidis. 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, mucusy, and bloody. Campylobacter is also associated with Guillain–Barre syndrome.^5–9