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Chapter 151: Inflammatory Bowel Diseases

INTRODUCTION

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of unknown etiology involving the gastrointestinal (GI) tract. Peak occurrence is between ages 15 and 30 and between ages 60 and 80, but onset may occur at any age. Epidemiologic features are shown in Table 151-1. Pathogenesis of IBD involves activation of immune cells by unknown inciting agent (? microorganism, dietary component, bacterial or self-antigen) leading to release of cytokines and inflammatory mediators. Genetic component suggested by increased risk in first-degree relatives of pts with IBD and concurrence of type of IBD, location of Crohn’s disease (CD), and clinical course. Reported associations include HLA-DR2 in Japanese pts with ulcerative colitis (UC) and a CD-related gene called CARD15 on chromosome 16p. CARD15 mutations may account for 10% of CD risk. Other potential pathogenic factors include serum antineutrophil cytoplasmic antibodies (ANCA) in 70% of pts with UC (also in 5–10% of CD pts) and antibodies to Saccharomyces cerevisiae (ASCA) in 60–70% of CD pts (also in 10–15% of UC pts and 5% of normal controls). Granulomatous angiitis (vasculitis) may occur in CD. Acute flares may be precipitated by infections, nonsteroidal anti-inflammatory drugs (NSAIDs), and stress. Onset of UC often follows cessation of smoking.

TABLE 151-1Epidemiology of IBD
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TABLE 151-1 Epidemiology of IBD
  ULCERATIVE COLITIS CROHN’S DISEASE
Incidence (North America) per person-years 0–19.2 per 100,000 0–20.2 per 100,000
Age of onset 15–30 and 60–80 15–30 and 60–80
Ethnicity Jewish > non-Jewish white > African American > Hispanic > Asian
Male/female ratio 0.51–1.58 0.34–1.65
Smoking May prevent disease (OR 0.58) May cause disease (OR 1.76)
Oral contraceptives No increased risk OR 2.82
Appendectomy Protective (risk 13–26% lower) Not protective
Monozygotic twins 6–18% concordance 38–58% concordance
Dizygotic twins 0–2% concordance 4% concordance
Antibiotic use in the first year of life 2.9× the risk of developing childhood IBD  

Abbreviations: IBD, inflammatory bowel disease; OR, odds ratio.

ULCERATIVE COLITIS

PATHOLOGY

Colonic mucosal inflammation; rectum almost always involved, with inflammation extending continuously (no skip areas) proximally for a variable extent; histologic features include epithelial damage, inflammation, crypt abscesses, loss of goblet cells.

CLINICAL MANIFESTATIONS

Bloody diarrhea, mucus, fever, abdominal pain, tenesmus, weight loss; spectrum of severity (majority of cases are mild, limited to rectosigmoid). In severe cases, dehydration, anemia, hypokalemia, hypoalbuminemia.

COMPLICATIONS

Toxic megacolon, colonic perforation; cancer risk related to extent and duration of colitis; often preceded by or coincident with dysplasia, which may be detected on surveillance colonoscopic biopsies.

DIAGNOSIS

Sigmoidoscopy/colonoscopy: mucosal erythema, granularity, friability, exudate, hemorrhage, ulcers, inflammatory polyps (pseudopolyps). Barium enema: loss of haustrations, mucosal irregularity, ulcerations.

CROHN’S DISEASE

PATHOLOGY

Any part of GI tract, usually ...

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