# Inflammatory Bowel Disease: Pediatric Onset and Lifelong Management

## Overview
Up to 25% of inflammatory bowel disease (IBD) presents before age 18. Pediatric-onset IBD tends to be more extensive, more aggressive, and more likely to require early immunomodulation or biologic therapy. Growth failure and pubertal delay add unique pediatric dimensions. The Med-Peds physician must understand the differences in disease behavior, management philosophy, and transition challenges between pediatric and adult IBD care.

## Classification

### Crohn Disease (CD)
Can affect any part of the GI tract (mouth to anus); skip lesions; transmural inflammation. Montreal classification (location): L1 ileal, L2 colonic, L3 ileocolonic, L4 upper GI (modifier) Montreal classification (behavior): B1 non-stricturing/non-penetrating, B2 stricturing, B3 penetrating; p perianal modifier. Paris classification (pediatric modification): adds L4a (proximal to ligament of Treitz) and L4b (distal small bowel), and growth impairment (G0/G1)

### Ulcerative Colitis (UC)
Limited to colon and rectum; continuous inflammation; mucosal/submucosal involvement. Montreal classification (extent): E1 proctitis, E2 left-sided, E3 pancolitis. Pediatric UC is more likely to present with pancolitis (E3) -- approximately 60-80% vs. 30-40% in adults.

### IBD-Unclassified (IBD-U)
10-15% of pediatric IBD; features of both CD and UC without clear distinction. More common in young children (<6 years)

## Epidemiology
Pediatric IBD incidence: approximately 10 per 100,000 children/year (rising globally) Bimodal age distribution of IBD: peak at 15-30 years (adolescents/young adults) and 50-70 years. Very early onset IBD (<6 years): consider monogenic forms (IL-10 receptor deficiency, XIAP deficiency, CGD) Geographic variation: highest in North America and Northern Europe; rapidly increasing in Asia.

## Clinical Presentation

### Pediatric IBD
**Crohn disease**: abdominal pain (often right lower quadrant), diarrhea (may be non-bloody), weight loss, growth failure (may be the ONLY presenting sign), fatigue, perianal disease (fistulae, tags, abscesses), oral aphthous ulcers, fever. **Ulcerative colitis**: bloody diarrhea, urgency, tenesmus, abdominal cramping, occasionally toxic megacolon at presentation. **Growth failure**: linear growth deceleration, delayed bone age, pubertal delay; may precede GI symptoms by months to years. Mechanism: chronic inflammation (IL-6, TNF-alpha suppress IGF-1), inadequate nutrition, corticosteroid effects. Screening: plot height velocity on growth chart at every visit; compare to mid-parental height. **Extraintestinal manifestations**: occur in 25-35% of pediatric IBD. Musculoskeletal: arthritis (most common EIM), sacroiliitis. Dermatologic: erythema nodosum, pyoderma gangrenosum. Ophthalmologic: uveitis, episcleritis. Hepatobiliary: primary sclerosing cholangitis (more common in pediatric UC) Hematologic: anemia (iron deficiency + anemia of chronic disease), VTE risk.

### Adult IBD
Similar GI symptoms but growth is not a concern. Extraintestinal manifestations same spectrum. Higher rates of stricturing and penetrating Crohn disease at diagnosis (may reflect delayed diagnosis or age-related disease progression) Greater burden of comorbidities (cardiovascular, metabolic) affecting treatment decisions.

## Diagnosis

### Laboratory
CBC: anemia (iron deficiency, B12/folate in ileal CD), thrombocytosis. CRP and ESR: elevated in active inflammation; CRP more specific. Albumin: low in severe disease (malnutrition and protein-losing enteropathy) **Fecal calprotectin**: excellent non-invasive marker of intestinal inflammation; levels >250 mcg/g highly suggestive of IBD; useful for monitoring and distinguishing IBD from IBS. Celiac serology: to exclude celiac disease (mimics IBD) Stool studies: C. difficile, enteric pathogens (to exclude infectious causes)

### Endoscopy
**Upper and lower endoscopy with biopsies**: gold standard for diagnosis in both children and adults. Pediatric-specific: upper endoscopy should be performed in ALL children with suspected IBD (higher rate of upper GI Crohn involvement) Histology: granulomas (pathognomonic but present in only 30-50% of CD), crypt distortion, chronic inflammation.

### Imaging
**MR Enterography (MRE)**: preferred cross-sectional imaging (no radiation); evaluates small bowel inflammation, strictures, fistulae, abscesses. **Wireless capsule endoscopy**: small bowel visualization when MRE is equivocal; patency capsule first if stricture suspected. **CT enterography**: adults when MRI not available; avoid in children due to radiation. **Pelvic MRI**: perianal Crohn disease assessment.

## Disease Activity Assessment
**Pediatric CD Activity Index (PCDAI)**: validated for children <18; scores based on symptoms, exam, labs, growth. **Pediatric UC Activity Index (PUCAI)**: symptom-based scoring; remission <10, mild 10-34, moderate 35-64, severe >=65. **Adult**: CDAI (Crohn Disease Activity Index), Mayo score (UC), Harvey-Bradshaw Index (simplified CD) **Mucosal healing**: increasingly the treatment target; endoscopic remission (SES-CD <3 for CD, Mayo endoscopic subscore 0-1 for UC)

## Management

### Treatment Goals
Induce and maintain clinical and endoscopic remission (mucosal healing); Restore and maintain normal growth and development in children; Minimize corticosteroid exposure; Prevent complications (strictures, fistulae, colorectal cancer); Optimize quality of life and psychosocial functioning.

### Induction Therapy

#### Corticosteroids
Prednisone/prednisolone: 1-2 mg/kg/day (max 40-60 mg) for moderate-severe flares; taper over 8-12 weeks. Budesonide (enteric-coated): for mild-moderate ileal/right-sided Crohn disease; less systemic side effects. IV methylprednisolone: for severe/fulminant disease (hospitalized patients) Corticosteroids are INDUCTION only -- never maintenance; growth suppression in children is a critical concern.

#### Exclusive Enteral Nutrition (EEN)
First-line induction therapy for pediatric Crohn disease in many centers (ECCO/ESPGHAN guidelines) Polymeric formula delivered orally or via NG tube for 6-8 weeks as sole nutrition source. Equivalent efficacy to corticosteroids for inducing remission WITHOUT steroid side effects. Promotes mucosal healing and improves nutrition/growth. Underutilized in North America compared to Europe/Australia/Japan. Not effective for UC.

### Maintenance Therapy

#### 5-ASA (Mesalamine)
Mild UC: first-line maintenance. No role in Crohn disease maintenance (SONIC trial demonstrated inferiority) Formulations: oral (Asacol, Lialda, Pentasa) and rectal (suppositories, enemas for proctitis/left-sided UC)

#### Thiopurines (Azathioprine, 6-Mercaptopurine)
Historically mainstay of maintenance therapy. TPMT/NUDT15 genotyping: MUST check before starting (homozygous deficiency causes severe myelosuppression) Monitoring: CBC q3 months, LFTs. Risks: lymphoma (hepatosplenic T-cell lymphoma -- rare but fatal, especially in young males on thiopurine + anti-TNF), non-melanoma skin cancer, infections. Increasingly being supplanted by earlier biologic therapy.

#### Methotrexate
Crohn disease maintenance (not UC); 15 mg/m2 subcutaneous weekly (pediatric); 25 mg SC weekly (adult); Requires folic acid supplementation; monitor CBC and LFTs; Teratogenic -- strict contraception required.

#### Biologic Therapies

| Agent | Mechanism | Indication | Pediatric Approval |
|-------|-----------|------------|-------------------|
| Infliximab | Anti-TNF-alpha | CD and UC | >=6 years |
| Adalimumab | Anti-TNF-alpha | CD (and UC in adults) | >=6 years |
| Vedolizumab | Anti-alpha4beta7 integrin (gut-selective) | CD and UC | Off-label in children |
| Ustekinumab | Anti-IL-12/23 (p40) | CD (and UC in adults) | Off-label in children |
| Risankizumab | Anti-IL-23 (p19) | CD | Adults; pediatric trials ongoing |
| Ozanimod | S1P receptor modulator | UC | Adults |
| Upadacitinib | JAK inhibitor | UC and CD | Adults (>=18) |

#### Top-Down vs. Step-Up
**Step-up**: traditional approach; start with 5-ASA or steroids, escalate to immunomodulators, then biologics. **Top-down**: early biologic (anti-TNF) + immunomodulator; evidence from SONIC trial (adults) and pediatric studies shows higher mucosal healing rates. Top-down increasingly favored in pediatric CD, especially with high-risk features (deep ulcers, extensive disease, perianal disease, growth failure, severe presentation)

### Surgical Management
**Crohn disease**: surgery is NOT curative; reserved for complications (stricture, abscess, fistula refractory to medical therapy); ileocecal resection for localized disease. **Ulcerative colitis**: total proctocolectomy with ileal pouch-anal anastomosis (IPAA) is curative; indicated for refractory disease, toxic megacolon, dysplasia/cancer. Pediatric surgical considerations: staged procedures, growth implications, quality of life with ileostomy/pouch.

## Monitoring and Surveillance
Regular assessment with fecal calprotectin (non-invasive), CRP, CBC, albumin. Periodic endoscopy: mucosal healing assessment; colonoscopic surveillance for dysplasia starting 8 years after diagnosis (UC and Crohn colitis) Drug level monitoring: trough levels and anti-drug antibodies for anti-TNF agents (therapeutic drug monitoring or TDM) Growth monitoring: height velocity, bone age, pubertal staging (Tanner) at every visit in children. Bone density: DXA scan if chronic steroid exposure or other risk factors. Vaccinations: ensure up-to-date BEFORE starting immunosuppression; avoid live vaccines while on immunosuppressive therapy.

<image>A comprehensive comparison diagram showing pediatric versus adult IBD characteristics. Two parallel columns display differences in: disease extent at diagnosis (pediatric UC more likely pancolitis, pediatric CD more extensive), unique pediatric features (growth failure, pubertal delay, very early onset forms), treatment philosophy (EEN as first-line induction for pediatric CD, top-down approach increasingly favored), and monitoring priorities (growth velocity charts in children, colonoscopic surveillance in both). A central overlap zone shows shared features and medications used across ages.</image>

<image>A treatment algorithm for pediatric Crohn disease showing the decision pathway from diagnosis through management. Starting with disease severity and phenotype assessment, the flowchart branches to: mild disease (EEN or budesonide for ileal), moderate disease (EEN or corticosteroids for induction, then thiopurine or methotrexate for maintenance), and severe/high-risk disease (top-down approach with anti-TNF plus immunomodulator, with EEN as bridge). Response assessment at 8-12 weeks leads to continuation, dose optimization via TDM, or switch to alternative biologic class. Growth velocity is shown as a parallel monitoring track throughout.</image>

<image>An infographic illustrating the concept of growth failure as a presenting sign of pediatric IBD. A growth chart shows a child's height trajectory declining from the 50th percentile to below the 5th percentile over 2 years before GI symptoms develop. Alongside, the mechanisms are shown: TNF-alpha and IL-6 suppressing IGF-1 and growth hormone signaling at the growth plate, inadequate caloric intake, and corticosteroid-mediated growth suppression. The bottom section shows growth recovery after effective anti-TNF therapy with catch-up growth trajectory.</image>

## Clinical Pearls
Growth failure may be the ONLY presenting sign of pediatric Crohn disease -- plot height velocity at every visit and investigate any deceleration. Pediatric UC presents with pancolitis in 60-80% of cases (vs. 30-40% in adults), reflecting more aggressive disease biology. Exclusive enteral nutrition is as effective as corticosteroids for inducing remission in pediatric Crohn disease without steroid side effects -- it is first-line per ECCO/ESPGHAN guidelines. ALWAYS check TPMT/NUDT15 genotype before starting azathioprine or 6-MP -- homozygous deficiency causes life-threatening myelosuppression. Top-down therapy with early biologic use is increasingly favored for high-risk pediatric Crohn disease to prevent complications and promote mucosal healing. Fecal calprotectin is an excellent non-invasive marker for monitoring disease activity and predicting relapse -- use it liberally. Ensure all vaccinations (especially live vaccines) are up-to-date BEFORE initiating immunosuppressive therapy. Therapeutic drug monitoring (TDM) for anti-TNF agents improves outcomes by identifying subtherapeutic levels and anti-drug antibodies early.

## References
- Rosen MJ, Dhawan A, Saeed SA. Inflammatory bowel disease in children and adolescents. JAMA Pediatr. 2015;169(11):1053-1060.
- Ruemmele FM, Veres G, Kolho KL, et al. Consensus guidelines of ECCO/ESPGHAN on the medical management of pediatric Crohn disease. J Crohns Colitis. 2014;8(10):1179-1207.
- Colombel JF, Sandborn WJ, Reinisch W, et al. Infliximab, azathioprine, or combination therapy for Crohn disease (SONIC trial). N Engl J Med. 2010;362(15):1383-1395.
- Turner D, Ruemmele FM, Orlanski-Meyer E, et al. Management of paediatric ulcerative colitis (ECCO/ESPGHAN 2018 guidelines). J Crohns Colitis. 2018;12(12):1517-1531.
- Levine A, Wine E, Assa A, et al. Crohn disease exclusion diet plus partial enteral nutrition induces sustained remission in a randomized controlled trial. Gastroenterology. 2019;157(2):440-450.