What is Inflammatory Bowel Disease (IBD) in pediatric patients?

What is Inflammatory Bowel Disease (IBD) in Children?

Inflammatory bowel disease (IBD) in children is a chronic immune-mediated disorder of the gastrointestinal tract that includes Crohn's disease and ulcerative colitis, with Crohn's disease accounting for approximately 65% of pediatric cases. 1

Epidemiology and Incidence

• The incidence of pediatric IBD in Canada is among the highest worldwide, reaching 9.68 per 100,000 children under age 16 years, and continues to increase particularly in children younger than 5 years. 1
• The prevalence of IBD is 100 to 200 cases per 100,000 children in the United States, with approximately 10 new cases per 100,000 children diagnosed annually. 1
• Twenty-five percent of all IBD patients are diagnosed before 20 years of age, with 18% diagnosed before 10 years of age. 1
• Pediatric-onset IBD most commonly develops in adolescence, though the highest percentage increases in incidence are among children younger than 5 years. 1

Pathophysiology

IBD results from a dysregulated mucosal immune response to intestinal microflora in genetically predisposed individuals. 2, 3

• The disease involves a complex interaction of genetic determinants, disruption of mucosal barriers, aberrant inflammatory signals, loss of tolerance, and environmental triggers. 3
• In genetically predisposed patients, the underlying mechanism is an inappropriate inflammatory reaction to intestinal flora. 1

Unique Pediatric Features

Disease Distribution Patterns

• Pediatric patients demonstrate more extensive colitis and less ileitis compared to adults, with an inverse linear relationship between age and Crohn's colitis through age 10. 1, 4
• Children are more likely to have upper gastrointestinal involvement than adults, with upper GI inflammation present in up to 75% of pediatric patients. 1, 4
• Perianal Crohn's disease occurs in 15% to 25% of pediatric patients. 1

Histopathological Differences

• Epithelioid-cell granulomas are more frequent in children with Crohn's disease, identified in 61% of untreated pediatric patients compared to lower rates in adults. 1, 4
• Granulomas at initial colonoscopy were recorded in 67% of children versus 66% of adults, but at subsequent colonoscopies in 54% of children versus only 18% of adults, suggesting granulomas may evolve or regress. 1
• Upper tract and terminal ileum biopsies are essential for identifying granulomas in 42% of pediatric patients. 1

Clinical Presentation

• Children can present with classic symptoms of weight loss, abdominal pain, and bloody diarrhea, but many present with nonclassic symptoms including isolated poor growth, anemia, or extraintestinal manifestations. 2
• In children with severe Crohn's disease, all biopsies obtained during colonoscopy may show chronic inflammation including the rectal mucosa, introducing diagnostic difficulties in differentiating between Crohn's disease and ulcerative colitis. 1

Disease Classification

Very Early Onset IBD (VEOIBD)

Children presenting under age 5-6 years require evaluation for underlying primary immunodeficiency disorders before initiating standard IBD therapy, as very early onset IBD may represent monogenic disorders requiring genomic testing rather than standard immunosuppression. 5

• VEOIBD may represent a distinct entity with more severe disease behavior. 5, 4

Inflammatory Bowel Disease Unclassified (IBDU)

• IBDU is used when there are clinical and endoscopic signs of chronic colitis without specific features of ulcerative colitis or Crohn's disease but features of both. 6
• Pediatric-onset IBDU is more common than adult-onset IBDU. 6

Diagnostic Approach

Endoscopic Evaluation

• Ileocolonoscopy with biopsies is essential in all children with suspected IBD, and esophagogastroduodenoscopy should be routinely performed to improve diagnostic accuracy. 5
• Multiple biopsies should be taken from the ileum and each colonic segment, including the rectum, to assess disease distribution. 5
• Biopsies from endoscopically bland, apparently non-affected areas should always be included in patient evaluation. 1

Laboratory Screening

• Laboratory screening at diagnosis should include complete blood count, hepatitis B and C serologies, varicella zoster virus serology, Epstein-Barr virus serology, tuberculosis screening, and stool examination for infectious causes before starting immunosuppression. 5

Imaging

• Both MR enterography and CT enterography are appropriate imaging modalities for assessing bowel not amenable to endoscopy, detecting transmural disease, and evaluating extraluminal complications. 1

Unique Pediatric Challenges

Growth and Development

Growth impairment is a direct effect of persistent chronic inflammation and represents a unique pediatric concern requiring aggressive disease control. 1

• Growth failure and pubertal delay require close monitoring at every visit, including height, weight, and pubertal development. 5
• Nutritional support is particularly important for children with growth failure and active small bowel disease. 5

Bone Health

• Monitoring bone health, including vitamin D and calcium levels, is essential, with consideration for bone density assessment in patients with chronic disease or prolonged steroid exposure. 5

Psychosocial Considerations

• Unique challenges include the psychology of adolescence and development of body image. 7
• Many patients continue to experience nonspecific symptoms like abdominal pain and fatigue even after remission. 7

Treatment Goals

Intestinal healing, rather than symptom control alone, has become the critical therapeutic goal in pediatric IBD. 1

• This is especially important in young patients given the potential for growth impairment and their long lives ahead during which disease complications may occur. 1
• Mucosal healing became a realistic goal with the advent of monoclonal antibodies directed against tumor necrosis factor-α. 1
• Biochemical or endoscopic remission, rather than clinical remission, is the therapeutic goal because intestinal inflammation often persists despite resolution of abdominal symptoms. 7

Common Pitfalls

• Failing to consider VEOIBD as a potential manifestation of underlying immune deficiency in children under 6 years. 5, 4
• Missing granulomatous inflammation due to inadequate tissue sampling, particularly from the upper gastrointestinal tract. 1, 4
• Overlooking the possibility of ulcerative colitis in young children with atypical histological presentation, including rectal sparing which is more common in children than adults. 4
• Assuming that rectal sparing excludes ulcerative colitis in pediatric patients. 4