Bacterial, parasitic, or viral infection (see Chapter 27, “Diarrhea, Acute”)

Small bowel bacterial overgrowth

Postinfectious enteritis

Necrotizing enterocolitis

Antibiotics

Laxatives

Mannitol

Motility agents

Chemotherapeutic agents

Neuroblastoma

VIPoma

Gastrinoma

Lymphoma

Polyposis

Mastocytosis

Carbohydrate malabsorption—lactose intolerance, fructose intolerance, glucose–galactose transporter defect, and sucrase-isomaltase deficiency

Fat malabsorption—congenital lipase deficiency, pancreatic disease (cystic fibrosis, chronic pancreatitis, Shwachman syndrome), chronic liver disease, congenital bile salt malabsorption, and Wolman disease

Protein-losing enteropathy (PLE)—intestinal lymphangiectasia or secondary causes

Congenital chloride diarrhea

Congenital sodium diarrhea

Acrodermatitis enteropathica

Hyperthyroidism

Hypoparathyroidism

Congenital adrenal hyperplasia

Diabetes

Lipoprotein disorders

Malrotation

Partial small bowel obstruction

Short bowel syndrome

Blind loop syndrome

Fistula

Pyloroplasty

Hirschsprung disease with enterocolitis

Overfeeding (food or liquid)

Food allergy

Allergic proctocolitis

Eosinophilic gastroenteritis

Malnutrition

Excessive fructose intake

Fiber

Sorbitol

Celiac disease

Inflammatory bowel disease

Severe combined immunodeficiency

Immunoglobulin A (IgA) deficiency

Autoimmune enteropathy

Hemolytic uremic syndrome (HUS)

Munchausen by proxy syndrome

Chronic nonspecific diarrhea of infancy

Irritable bowel syndrome

Hepatobiliary disorders (hepatitis, cholestasis, cholecystectomy)

Encopresis

Radiation enteritis

Neonatal drug withdrawal syndrome

Chronic nonspecific diarrhea of infancy (also known as toddler’s diarrhea) is the most common cause of diarrhea in children between 6 months and 3 years of age.

The cause is unclear. The disorder may be related to increased bowel motility or low intake of fat and fiber, or it may follow a bout of infectious gastroenteritis.

Patients pass 3 to 10 loose stools per day, usually diminishing in frequency in the evening. The child has a good appetite and appropriate weight gain, although undigested food particles are visible in the stool.

The diagnosis is by exclusion of other causes. Workup for infection and malabsorption are negative. Stool testing for occult blood is also negative. Clinically, a history of excessive intake of juices and a diet low in fat and fiber in a child who is thriving supports the diagnosis.

Infectious enteritis is the most common cause of chronic diarrhea. Gastrointestinal infections are usually acute and resolve in ˜2 weeks, but sometimes they can persist for as long as 2 months. Viral gastroenteritis in an infant can be prolonged as a result of the slow healing of the intestinal mucosa. In addition, infections tend to last longer than usual in immunocompromised patients.

Common bacterial causes of chronic diarrhea include Salmonella, Shigella, Yersinia enterocolitica, Campylobacter, enteroadherent Escherichia coli, Aeromonas, Clostridium difficile, and Plesiomonas. Parasitic causes include Giardia lamblia, Cryptosporidium, Entamoeba histolytica, and Isospora. Rotavirus, adenovirus, and norovirus are common viral causes.

Y. enterocolitica infection involves the terminal ileum and can mimic inflammatory bowel disease or appendicitis. It is more common in patients whose normal bowel flora has been changed secondary to antibiotic therapy.

E. histolytica infection can cause colitis. Blood, mucus, or both are seen in the stool, and patients have a fever.

Giardia lamblia infection is usually asymptomatic but may manifest with bloating, abdominal pain, anorexia, chronic diarrhea, and failure to thrive (see Chapter 10, “Abdominal Pain, Chronic”).

C. difficile infection most commonly occurs following a course of oral antibiotics, although nonantibiotic associated infections are also common.

A stool sample should be obtained for bacterial and viral culture. The laboratory should be instructed to culture for all of the most commonly implicated bacteria and viruses. Stool samples for rotazyme (an enzyme-linked immunoassay for rotavirus) and assays for C. difficile toxins A and B should also be obtained.

PCR analysis can be performed for viral infections. Three stool specimens should be submitted for ova and parasites (O&P) analysis.