DIARRHEA

Faria Pereira, MD and Deborah Hsu, MD, MEd

Diarrhea, defined as a decrease in the consistency of the stool (loose/watery) and/or greater than three stools in a 24-hour period, is a common presenting complaint to the emergency department (ED). Infants and children have variability in frequency and type of stools; therefore, any deviation from the usual stooling pattern should arouse at least a mild concern, regardless of the actual number of stools or their water content. An acute diarrheal illness typically lasts less than 5 days. In the United States, diarrhea accounts for approximately 1.5 million annual outpatient visits. Although most bouts of illness are self-limited, approximately 200,000 patients are hospitalized and 300 die each year. Since the introduction of the rotavirus vaccine in 2006, the number of hospitalizations due to diarrheal disease has been reduced.

DIFFERENTIAL DIAGNOSIS

Diarrhea may be the initial manifestation of a wide spectrum of disorders as outlined in Table 18.1. The most common etiology for diarrhea in pediatric patients presenting to the ED is viral gastroenteritis, with rotavirus and norovirus being the most common agents. Other causes include bacterial and parasitic infections, parenteral diarrhea (nongastrointestinal infection such as otitis media), and antibiotic induced. The emergency physician must be vigilant in recognizing the few children who have diseases that are likely to be life-threatening from among the majority of children who have self-limiting infections. Particularly urgent are intussusception, hemolytic uremic syndrome (HUS), pseudomembranous colitis, and appendicitis (Table 18.2). In addition, children may develop severe dehydration with diarrhea secondary to any etiology.

Intussusception is a potentially life-threatening condition that can present with bloody diarrhea, although this is not the typical presenting complaint. Intussusception peaks in frequency between 5 and 10 months of age and tapers off rapidly after 2 years of age unless there is a predisposing pathologic condition. This topic is covered in more detail in Chapter 48 Pain: Abdomen.

HUS should also be considered in a child presenting with bloody diarrhea. HUS is an uncommon but potentially life-threatening disease that typically presents with the classic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Children are affected most often in the first 3 years of life. They often present with abdominal pain, vomiting, and diarrhea that become bloody. Five to 10 days after onset of diarrhea, children with HUS develop pallor, petechiae, and decreased urine output. The most common cause of HUS is Shiga-like toxin-producing Escherichia coli (E. coli 0157:H7).

Pseudomembranous colitis is another serious disorder that may cause bloody diarrhea. Clinically, the child with pseudomembranous colitis appears ill with prostration, abdominal distention, and blood in the stool. This disease results from an overgrowth of toxin-producing Clostridium difficile, usually as a result of destruction of the normal intestinal microflora. It may occur at any age but is uncommon in early childhood. Although the incidence of pseudomembranous colitis is highest after treatment with clindamycin, studies have shown that exposure to any antibiotic increases susceptibility to C. difficile infection. In fact, because of its common use, amoxicillin is responsible for most cases of pseudomembranous colitis in childhood, even though overall incidence of C. difficile infection after therapy with this agent is low. Occasional cases occur in children with no recent usage of antibiotics.

Appendicitis manifests primarily with abdominal pain. Common presentation is periumbilical abdominal pain that migrates to the right lower quadrant, followed by anorexia, vomiting, and/or fever. Less commonly, appendicitis may cause diarrhea. The presumed mechanism for the diarrhea is irritation of the colon by the inflamed appendix. Particularly in very young children or among patients of any age who have a perforated appendix and a long duration of illness, the diagnosis of appendicitis as the cause of diarrhea may be delayed because the classic constellation of signs and symptoms is often absent. However, the examiner will usually be able to elicit abdominal tenderness greater than would be expected with gastroenteritis.

Toxic megacolon is a life-threatening condition that can occur as a complication of a number of conditions including inflammatory bowel disease (IBD), shigella infection, pseudomembranous colitis, and Hirschsprung disease. It is characterized by a dilated colon and abdominal distention with abdominal pain and fever that may progress to shock.

EVALUATION AND DECISION

The history and physical examination are paramount in determining if the child with diarrhea has a mild self-limiting illness or a condition that is potentially life-threatening. Further, the physician must also identify if the diarrheal illness is acute or chronic as the etiologies can be different.

In evaluating a child with diarrhea, a rapid assessment is necessary to determine the need for urgent or emergent fluid resuscitation. Historical information that should be elicited include detailed questions about the onset of illness, frequency (number of diarrheal stools per day), quantity (smear in the diaper or stool fills and overflows the diaper in infants), and characteristics (e.g., bloody, mucoid, black) of stools, presence of concurrent vomiting, the amount of liquid taken orally, and the frequency or volume of urination (number of wet diaper changes in the infant).

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