Approximately two million people worldwide are afflicted with IBD. IBD is more common in westernized societies and in the northern hemisphere. There is a higher incidence in Caucasians and those of Jewish descent, which may reflect both genetic and environmental contributions. Approximately 12% to 30% of all patients with IBD present during childhood (before 20 years of age).^1–3 Pediatric incidence is increasing; currently it is estimated at 0.5 to 34/100,000 for ulcerative colitis (UC) and 0.2 to 58/100,000 for Crohn’s disease (CD).^3–8 UC and CD occur equally in the first 8 years of life; CD is more common in older children.⁹ Most children with IBD present in late childhood/early adolescence, but diagnosis in infancy has been described.^1,10,11

PATHOPHYSIOLOGY

The exact pathophysiology of IBD is not well understood. There is likely a combination of environmental, genetic, and immune factors. An environmental trigger may incite a deregulation of immune response to gut flora in a genetically susceptible host.^12–15 Patients with IBD have less complex profiles of commensal bacteria and higher numbers of mucosa-associated bacteria as compared to healthy individuals.¹² Increased intestinal permeability and food-borne bacterial infections trigger some IBD cases.

Although development of IBD is multifactorial, there are many known risk factors. A family history of IBD carries an 8- to 10-fold greater risk and IBD frequency in first-degree relatives may be as high as 40%.^4,16 IBD is particularly severe in Jewish persons with familial Mediterranean fever.¹⁷ Pediatric IBD has a stronger genetic correlation, possibly because children have less lifetime exposure to environmental factors.^18–20 Infections are also associated with IBD. C. difficile infection can be either an inciting or exacerbating factor.²¹ An increased risk of IBD has been shown in persons after acute gastroenteritis with Salmonella or Campylobacter.^22,23 The risk is highest during the first year after the gastroenteritis episode, but remains high compared to matched controls for up to 15 years.²³ Other environmental risk factors include smoking (in CD; smoking is protective against UC), exclusive formula-feeding, a diet high in animal protein and low in fiber,^24–27 climate, low vitamin D exposure,^28,29 and stress.⁴ Exercise may be protective against flares.³⁰

CLINICAL PRESENTATION

Pediatric patients with IBD typically present with signs and symptoms of colitis. Often, they have a subacute illness with abdominal pain and diarrhea (frequently bloody). Fever, fatigue, anemia, and weight loss are also common presenting symptoms in IBD. Symptoms may be persistent (≥4 weeks) or recurrent (≥2 episodes in 6 months).³¹ EIMs occur in 6% of children upon presentation and in 25% to 35% of children overall.¹⁸ IBD relapse can be precipitated by bacterial, parasitic, or viral superinfection. C. difficile and cytomegalovirus (CMV) are both the most common and most challenging to manage.²¹

INDETERMINATE COLITIS

Younger children (<8 years of age) with IBD are more likely to have isolated colonic disease. Often, because the diagnosis of either UC or CD is initially unclear, children are labeled as having indeterminate colitis (IC). There is no widely accepted definition of IC; thus, IC includes a heterogeneous subset of patients. Three percent to 30% of pediatric IBD is termed IC.³²

ULCERATIVE COLITIS

UC is limited to the colon and involves the superficial mucosa. Typically, there are continuous lesions that start from the rectum. The mucosa is friable, and bleeding may occur spontaneously. With severe disease, ulcerations may develop, and rarely, lesions penetrate the muscularis layer.³³ The rectum is always involved in adults, but not in children. At presentation, 44% to 49% of children with UC have rectosigmoid disease, 36% to 41% have left-sided disease, and 14% to 27% have pancolitis.⁴ Childhood UC tends to be more severe compared to adult-onset disease. Approximately 80% to 90% of children either present with or progress to pancolitis (in contrast to 40%–50% of adults).³⁴ There is a shorter time from diagnosis to first surgery in children with UC as compared to adults. One study demonstrated that at 10 years after diagnosis, 40% of childhood-onset UC had required a colectomy versus 20% of adult-onset UC.³⁵ In the majority of patients, the clinical course involves disease flares alternating with periods of remission. A minority of patients have continuous activity. Overall, disease activity tends to decrease over time.

CROHN’S DISEASE

CD is marked by transmural bowel wall inflammation throughout the gastrointestinal tract. Normal mucosa surrounds diseased segments (skip lesions). In both children and adults, CD most commonly affects the terminal ileum and right colon. Younger children have predominantly colonic disease,^34,36 though the upper gastrointestinal tract is involved in up to two-thirds of children with CD.³⁷ The most common presenting symptoms of CD include abdominal pain, diarrhea, rectal bleeding, and weight loss. CD often has a more insidious onset, and patients present with vague complaints of malaise and mild abdominal discomfort. EIM can dominate the clinical picture and may even be present prior to gastrointestinal symptoms in children.³⁸ Growth and sexual developmental delay also may precede intestinal symptoms.³¹ Diagnostic delays of months are common. The clinical course of pediatric CD tends to be more severe as compared to adults. The course is unpredictable, with recurrent exacerbations of symptoms, and more rarely, continuous active disease. Ulcerations may become deep and cause complications such as abscess, fistulas, strictures, and obstruction from adhesions. Small bowel disease results in obstruction, and colonic involvement often presents with bleeding. There is no direct correlation between symptoms and progression of anatomic damage. A small segment of ileitis can cause severe abdominal pain and fatigue, whereas strictures and fistulas may be asymptomatic for years.²

The physical examination in pediatric IBD varies greatly depending on the location and severity of the involved gastrointestinal tract. Oral ulcers may be noted in CD. Abdominal tenderness may be mild, localized, or diffuse in both CD and UC. The abdomen may be rigid or peritoneal in severe acute colitis, toxic megacolon, or intestinal perforation. A palpable mass may be present in CD, as well as perianal involvement such as fistulae, anal tags, abscesses, or fissures. Gross or occult stool blood is often present.

EXTRAINTESTINAL MANIFESTATIONS

EIMs occur in 25% to 35% of children with IBD and are more common in children as compared to adults (see Table 76-1). Growth failure is the most common EIM in pediatric IBD. Inadequate nutrition, chronic steroid use, and decreased physical activity contribute to growth delays. Up to 46% of children will have a reduced height velocity before the onset of symptoms.³⁹ CD with perianal involvement portends a higher risk for EIM than other IBD patients. Patients who develop one EIM are more likely to develop additional EIMs.⁴⁰

There are no specific diagnostic criteria for IBD. Clinical suspicion is based on a combination of patient symptoms and screening laboratory data. Diagnosis is confirmed with radiographic studies and endoscopy +/– biopsy.

LABORATORY TESTING

Normal laboratory test results do not exclude the diagnosis of IBD.^31,41 Fecal calprotectin is the most sensitive test for inflammatory gastrointestinal disease and may be used in combination with C-reactive protein (CRP) and albumin to screen for IBD.⁴¹ Other laboratory abnormalities seen include anemia, thrombocytosis, increased erythrocyte sedimentation rate (ESR) (particularly in CD) and mild elevation of AST and ALT. Low albumin is commonly present because of malnutrition in children with IBD.⁴² Laboratory findings are more likely to be abnormal with severe disease. There is poor sensitivity and specificity of serology panels in screening for IBD. The most widely used diagnostic panel in the United States is the IBD Serology 7 panel.⁴³ Anti-Saccharomyces cerevisiae antibody (ASCA) and perinuclear antineutrophil cytoplasmic antibody (pANCA) are disease-specific for CD and UC, respectively. Blood and leukocytes are commonly present in stool. In acute exacerbation, stool culture should be sent in children with bloody diarrhea to evaluate for Salmonella, Shigella, Yersinia, Campylobacter, C. difficile, Giardia, Escherichia coli 0157:H7, Entamoeba, and tuberculosis. The incidence of C. difficile is greater in children as compared to adults and frequently correlates with severity of disease in young children.^42,44

DIAGNOSTIC IMAGING FOR IBD

Endoscopy

Frequently, there is endoscopic overlap between CD and UC. Diffuse colonic involvement is common in both pediatric UC and CD, and both may have gastric ulcers.

Crohn’s Disease

Ileal inflammation is present in most CD. Non-necrotizing granulomas confirm the diagnosis of CD but are only present in approximately 50% to 60% of patients.⁴⁵ Cobblestoning (mucosal ulcerations interlaced with normal segments of bowel), bowel wall edema, bowel narrowing or obstruction, and enteric fistulas may be seen. Noncontinuous areas of affected bowel (skip lesions) are often present and there is frequently relative rectal sparing.

Ulcerative Colitis

Typically, diffuse and continuous inflammation starts at the rectum and extends proximally into the colon. Early in pediatric UC, atypical features can occur, with patchy disease and relative rectal sparing. Nonspecific inflammation in the upper gastrointestinal tract may occur in up to 75% of children with UC.³¹ “Backwash ileitis” occurs in 10% of UC patients with pancolitis.⁴⁵ Pseudopolyps, areas of regenerating mucosa from prior ulceration, are often present.

OTHER DIAGNOSTIC MODALITIES

In addition to endoscopy, an upper GI series is recommended to evaluate the small intestine. Upper GI with small-bowel follow-through has been the traditional method of evaluating the upper gastrointestinal tract for IBD. Ultrasound is not commonly used for IBD screening but may play a larger role in the future as bowel ultrasound becomes more established.^46,47 Intestinal hypervascularity and thickened bowel loops can be seen in active IBD. Mesentery can be evaluated and fluid collections and abscesses may be visualized. Ultrasound identifies terminal ileal disease better than proximal small bowel and colonic lesions. Advanced US techniques are emerging using oral, rectal, and even IV contrast to improve scan quality.⁴⁸ Ultrasound does not expose a child to radiation and is relatively inexpensive and accessible. CT with oral contrast can evaluate the bowel wall and lumen well, and may identify abscesses as well. MRI use is increasingly common in pediatric IBD for evaluation of the small bowel and extraintestinal findings, as it avoids the risk of radiation.^49–52 However, the technique is less well established and the ability to obtain an MRI without sedation is challenging in young children. Video capsule endoscopy is used in adults to evaluate CD severity. It is approved by the FDA for ages older than 10 years, but pediatric GI doctors have found the capsule helpful in diagnosing children as small as 11.5 kg with an acceptable complication rate. The benefit is the avoidance of radiation, sedation, or general anesthesia.^53–56

EMERGENCY DEPARTMENT IMAGING

An abdominal series may be used as an initial test in the emergency department (ED) to evaluate for serious complications of IBD. This may show bowel obstruction with air–fluid levels, free air suggestive of perforation, and evidence of toxic megacolon. Findings of toxic megacolon include colonic dilation with an abnormal mucosal contour which is typically most pronounced in the transverse colon. Acute dilatation of transverse colon to >5 to 6 cm with loss of haustral folds in the setting of a severe exacerbation of colitis is diagnostic in older children and adults of toxic megacolon. In children younger than 10 years, transverse colonic diameter of >4 cm is suggestive of toxic megacolon.⁵⁷ Ultrasound may be used in an acute exacerbation and can detect mesenteric inflammatory changes, lymphadenopathy, and abscesses. CT may be necessary in an emergent case to evaluate for perforation with an acute abdomen (Fig. 76-1).