Pediatric Primary Care Case Studies (99 page)

The major pathophysiologic dynamic in diarrhea is an alteration in the balance of fluid exchange across the intestinal wall, resulting in excess fluid elimination. It is a function of a relative increase in secretion of fluid into the bowel and decrease in absorption of fluid from the small bowel. There are four main types of diarrhea commonly seen in infants and children:

1.
Osmotic diarrhea:
Occurs when the concentration of nutrients and electrolytes in the intestine is high enough to be osmotically active. As a result, fluid is drawn into the intestine to dilute these particles. Intestinal tissue is not typically damaged in osmotic diarrhea. Malabsorption syndromes, lactose intolerance, overfeeding, and excessive ingestion of hypertonic juices are examples of causes of osmotic diarrhea.

2.
Secretory diarrhea:
Occurs when bacterial enterotoxins stimulate secretion of fluids and electrolytes from small intestinal crypt cells into the intestine. Absorption by the small intestine villous cells is also inhibited. The excess fluids result in diarrhea. Common agents leading to secretory diarrhea include
Aeromonas, Clostridium, E. coli, Salmonella, Shigella, Yersinia, Vibrio
, and
Giardia.

3.
Cytotoxic diarrhea:
Occurs when an agent (usually viral) destroys mucosal villous cells of the small intestine. Secretory cells tend to be spared, but shortened villi lead to decreased absorption of fluids and electrolytes. Rotavirus, Norwalk virus,
Cryptosporidium
, and
E. coli
bacteria are major causes of cytotoxic diarrhea.

4.
Dysenteric diarrhea:
Occurs when the bowel is inflamed, damaging the mucosa and submucosa. Subsequent edema, infiltration, and bleeding compromise the ability of the intestine to absorb water, nutrients, and electrolytes. This inflammatory process can occur with bacterial infections, celiac disease, and irritable bowel syndrome, affecting the functional ability of the bowel.

Acute versus Chronic Diarrhea

Acute diarrhea is typically defined as duration of diarrheal symptoms for 5 days or less. Chronic (or persistent) diarrhea is the presence of loose or more frequent stools for more than 2 weeks (Ghishan, 2004; Pickering & Snyder, 2004). Dehydration is a major cause of morbidity and mortality in acute diarrhea, less so in chronic diarrhea. Growth retardation, both physical and cognitive, is more commonly seen with chronic diarrhea, though this is more of a problem in developing countries than in the United States (Bhutta et al., 2008).

The etiology of chronic diarrhea may be age-related, with cow’s milk protein intolerance being the most common cause in infants. However, the causes of chronic diarrhea in young children are largely uncertain and probably multiple. Mucosa damaged by an episode of acute diarrhea may be slow to heal, limiting absorption from the gut and resulting in a persistent osmotic diarrhea. Allergies or food sensitivities, dietary or nutritional deficiencies, unknown pathogens, or underlying conditions (such as enzyme deficiency, celiac disease, or an autoimmunity) may cause chronic diarrhea (Bhutta et al., 2008). One study of children with persistent diarrhea in the United States found that 59% of the stool samples sufficient for analysis contained no pathogens, and another 17.9% contained only
C. difficile
and
E. coli
that appeared unrelated to the diarrhea (Vernacchio et al., 2006). This same study found that viruses most typically associated with persistent diarrhea were rotavirus, norovirus, and sapovirus; it remains unclear what role these viruses play in chronic diarrhea in developing countries where malnutrition and other diseases complicate the presentation (Bhutta et al.; Vernacchio et al.). Protracted diarrhea also can be caused if vomiting and gastroenteritis are managed by a high-carbohydrate, low-fat, and low-protein diet (Petersen-Smith & McKenzie, 2009).

In the United States, chronic nonspecific diarrhea of childhood (CNDC), also called toddler’s diarrhea or irritable colon of infancy, is usually a benign condition, but it often leads to an outpatient medical visit and must be evaluated to determine if treatment is necessary. CNDC is a diagnosis of exclusion. The term has been in the medical literature for over 50 years, and the characteristics of the condition specified in 1966 remain valid (Kleinman, 2005). These characteristics include (Davidson & Wasserman, 1966):

•   Diarrhea typically begins between 6 and 20 months of age (> 75%); 12% of infants presented with diarrhea before 6 months of age.

•   The child is growing and developing well.

•   The first stool of the day is large and semi-formed; subsequent stools are smaller and looser.

•   Most (87%) children have diarrhea with mucous.

•   A family history of functional bowel disorders is common.

Clearly, the history and physical examination are critical to identify the condition and possible underlying causes. Laboratory and diagnostic studies are ordered as indicated. Key factors to consider in assessing and managing chronic diarrhea are:

•   In CNDC, the best treatment is reassurance and returning the child to a full, normal diet for age. In Davidson and Wasserman’s study (1966), 88% of children with CNDC cleared by 39 months of age; another 10% by 48 months of age, without growth delay.

•   Treat underlying causes if known.

•   Treat the effects of diarrhea as indicated (e.g., oral or parenteral rehydration).

•   Refer to a gastroenterologist if:

   Newborns present with diarrhea in the first hours of life.

   The child has abnormal or delayed growth patterns.

   Severe illness is present.

What additional information do you need to help you make the determination about a telephone consultation versus having Sara come in for an office visit?

Risk Factors for Hospitalization and Death Due to Gastroenteritis

Before the initiation of treatment either by telephone or in person, one must review risk factors that place a child with gastroenteritis at increased risk for hospitalization or death (Fischer et al., 2007; Ho et al., 1988). These include:

•   Age < 12 months

•   Malnutrition

•   Immunodeficiency

•   Underlying disease

•   Low socioeconomic status of the family

•   Race

•   Maternal factors:

   Little prenatal care

   Low level of education

   Young