Crohn’s disease (CD) and ulcerative colitis (UC), collectively known as inflammatory bowel disease (IBD), are idiopathic, lifelong, destructive chronic inflammatory conditions of the gastrointestinal tract which typically manifest during late childhood and adolescence.¹ The burden of these chronic relapsing diseases and their devastating effects imposed on affected children and teenagers may be considerable. IBD is divided into CD and UC based on clinical characteristics, although 5% to 24 % of patients do not clearly fit into either category and are termed inflammatory bowel disease–unspecified (IBD-U).² Chronic inflammation in CD can involve any part of the gastrointestinal tract and is characterized by discontinuous inflammation with intervening areas of normal mucosa (skip lesions) and transmural inflammation, which can result in fistulae, perforations, and strictures. Finding of noncaseating granulomas histologically in the mucosal biopsies are hallmark of CD. Intestinal involvement of UC is limited to the colon and typically begins distally in the rectum and extends proximally. Inflammation in UC is superficial.

The etiopathogenesis of IBD has been linked to a combination of genetic and environmental factors, but the exact cause remains elusive.³ Current thinking suggests patients with a genetically determined predisposition develop an immune-mediated response to an environmental trigger or intestinal microbial dysbiosis, which leads to chronic dysregulated inflammation.⁴ The early discovery of several genes, including CARD15 and the OCTN cation transporter associated with CD lends support to this hypothesis.^5-7 Subsequent advances in the genetics of IBD have implicated many genes representing several aspects of intestinal homeostasis including maintenance of the epithelial barrier, immune surveillance, neutrophil dysfunction, defects in innate immunity, and intracellular processes (e.g. autophagy, oxidative stress, carbohydrate metabolism).⁸ This highlights the fact that IBD represents a heterogeneous group of diseases beyond the clinical phenotypes of CD versus UC.

Population-based studies suggest that IBD is unevenly distributed throughout the world, with the highest disease rates occurring in Western countries.⁹ Epidemiologic surveys have also suggested that IBD incidence rates have changed over the second half of the twentieth century, gradually increasing for both UC and CD.^10-12 Recently an epidemiological study was completed which evaluated all children in Wisconsin with a new diagnosis of IBD over an 8-year period.¹³ The incidence of IBD was 9.5 per 100,000 in children under 18 years of age. The incidence of IBD was noted to be equal among all ethnic groups. Children from sparsely as well as densely populated counties were also equally affected. Over a 4-year period of follow-up, 17% of children with CD and 13% of those with UC required surgery. This epidemiologic data highlights the importance for pediatric hospitalists to be knowledgeable in the care of children with IBD.

Patients with IBD can present with a diverse constellation of signs and symptoms. The clinical presentation of CD varies with the anatomic location(s) of involvement.^1,14 In UC the clinical presentation typically is more predictable since intestinal involvement is limited to the colon. In both conditions, the severity of inflammation usually, but not always, correlates with the severity of the clinical presentation. It is likely that a primary care provider taking care of adolescents will be faced with a diagnosis of IBD one to three times a year, and a busy hospital-based pediatric gastroenterology practice will diagnose as many as one case per week.¹⁵ Recognition of the various clinical presentations of IBD can aid in early diagnosis and initiation of therapy.

Symptoms in the patient presenting with IBD can include abdominal pain, hematochezia, diarrhea, anorexia, nausea, weight loss, fatigue, and oral ulcerations.^14,16 Signs can include abdominal tenderness, perianal skin tags or fistulae, other fistulae, delayed puberty, iron deficiency anemia, hypoalbuminemia, and signs of extra-intestinal complications. Laboratory tests frequently include an elevated ESR and C-reactive protein. IBD is a systemic disease with many extra-intestinal manifestations (Table 80-1).

The evaluation of a patient with possible IBD should be based on clinical suspicion and initial laboratory testing that usually will indicate if definitive endoscopic and/or radiologic procedures are necessary. Stool studies to exclude intestinal infections that can cause diarrhea and rectal bleeding such as Salmonella, Shigella, Campylobacter, Yersinia, Escherichia coli 0157/H7, and Clostridia difficile are imperative. Other diagnostic considerations in adolescents with abdominal pain and rectal bleeding include Henoch-Schonlein purpura,¹⁷ Behçet’s disease¹⁸ (considered a form of IBD but beyond the scope of this chapter), hemolytic–uremic syndrome,¹⁹ or systemic vasculitis. When an abdominal abscess is found during the investigation of abdominal pain, in addition to CD, a perforated appendix, trauma and gynecologic diseases must be considered.

The diagnosis of IBD is usually confirmed by a combination of clinical observations and laboratory, radiographic, endoscopic, and histological findings.¹ A detailed history and physical examination remain the most important aspects in the evaluation of a child with abdominal pain. The most appropriate diagnostic approach often includes complete blood count, ESR, CRP, albumin, and stool specimens to rule out bacterial and protozoal pathogens. Endoscopic examinations (upper endoscopy and colonoscopy) with mucosal biopsies to directly examine the mucosa are key components to confirm the diagnosis (Figure 80-1). An upper GI series with small bowel follow through is the primary tool for evaluation of the jejunum and proximal ileum. However, in the hospitalized patient, a CT scan²⁰ may be an important early step to rule out other important diseases such as appendicitis, and can reveal signs that may suggest CD²¹ (e.g. “creeping fat” in the mesentery). Other tests that have been useful in selected patients who may have occult small bowel CD include enteroclysis, MRI (enterography), and WBC scanning.^22-24 Capsule endoscopy may prove to be the most sensitive way to assess the small bowel.^25-27 The use of capsule endoscopy requires careful consideration, because there is a risk of impaction of the instrument in patients with narrowing of the intestines, which could necessitate surgery. This is a particularly important issue in the smaller child. Table 80-2 describes the suggested initial diagnostic evaluation in child with suspected IBD. A commercial serologic panel has been added to the armamentarium of the laboratory evaluation of patients with suspected IBD^28,29 (pANCA, ASCA, and OmpC). This panel may be a useful adjunct to conventional laboratory tests, but it has not replaced the need for definitive examinations such as endoscopy or radiologic evaluations.

Initial management of the patient hospitalized with IBD must be tailored to the degree of illness the patient is exhibiting. Primary interventions should be directed toward stabilizing the patient and ensuring emergent surgical intervention is not required while the evaluation proceeds. Intravenous fluids and/or transfusions may be required in the dehydrated or anemic patient. Careful attention to hydration status is critical in the patient with significant hypoalbuminemia. When appendicitis or other surgical emergencies are considered in the differential diagnosis, it is prudent to withhold oral intake and administer IV broad-spectrum antibiotics that cover intestinal flora (e.g. ampicillin + aminoglycoside + metronidazole). In less ill patients, oral intake can be permitted while the evaluation proceeds.