VCU Department of Radiology

DEFINITION:

A transmural granulomatous inflammatory disease that may affect any part of the GI tract from mouth to anus. 

EPIDEMIOLOGY:

• incidence: 5-11/100,000 

• age of onset: 

  • peak age of onset in 2nd and 3rd decades 

  • less than 5% present before 5 years of age : 

• M = F 

• whites > blacks 

PATHOGENESIS:

1. Etiology

• the exact etiology is unknown, infection or an autoimmune process has been suggested. Up to 10% of patients with Crohn's Disease have a family history of Irritable Bowel Disease. 

2. Anatomic Involvement

• terminal ileum + variable segments of the colon (particularly the ascending colon) - 50-60% 

• small bowel involvement only (most in terminal ileum) - 30-35% 

• large bowel only - 10-15% 

• the esophagus, stomach, or duodenum is involved in 30-40% of patients 

CLINICAL FEATURES:

1. Gastrointestinal Manifestations

• abdominal pain (75%) 

• diarrhea (65%) 

• weight loss (65%) 

• fever (50%) 

• growth retardation (25%) 

• nausea/vomiting (25%) 

• rectal bleeding (20%) 

• perirectal disease (15%) 

• extraintestinal manifestations (25%) 

2. Gastrointestinal Complications

1. Hemorrhage

2. Obstruction

3. Perforation

4. Abscess

5. Fistula Formation

6. Others

• toxic megacolon (3.7%) - increases to 11% if disease confined to colon 

• carcinoma - 20x greater risk than in general population

Imaging Studies:

1. Barium Enema

A. Single Contrast

• to identify colonic fissures 

• contraindicated in suspected cases of severe colitis 

B. Double Contrast (Air-Barium)

• to define mucosal defects - narrowing, stenotic areas, cobblestoning, filling defects 

2. Upper GI Series with Small Bowel Follow-through

• particularly to visualize the terminal ileum: 

• cobblestone appearance 

• deep ulcers 

• fistula 

• nodularity 

• stenotic areas (string sign) 

• thickened bowel wall 

3. Abdominal Ultrasound/CT

• bowel wall thickening 

• abscesses 

• fistula

• focal fat proliferation

Endoscopy/Colonoscopy:

1. Macroscopic

• focal or segmental inflammation with skip areas of normal mucosa 

• complications of inflammation: 

• cobblestone pattern (ulceration with regeneration and hyperplasia) 

• wall thickening with stricture formation 

• fissures, sinuses, ulcerations, fistulas, phlegmon (inflammatory masses) 

• matted adjacent loops of bowel 

2. Microscopic

A. Early Changes

• superfical aphtoid lesions of mucosa overlying lymphoid follicles; granulomas 

B. Later changes

1. Transmural Enterocolitis

• diagnostic with histopathology of intestinal lesions showing extensive infiltration with inflammatory cells 

• lymphocytes, histiocytes, plasma cells found throughout the bowel wall but extensively in the submucosa 

• collagen deposition within the submucosa leading to strictures +/- obstruction 

• deep fissuring ulceration into the muscularis propria 

• crypt abscesses and goblet cell depletion 

2. Granulomas

• may be absent in 60-70% of biopsies 

Goals of Therapy:

• therapy (pharmacolgic, nutritional, or surgery) is not curative 

• no prophylactic role of therapy 

• goal is to control symptoms, prevent complications, improve growth, and to induce remission during an acute episode by either pharmacologic, nutritional and/or surgical strategies 

Prognosis:

• Crohn's Disease at this time is a chronic incurable disease of the bowel marked by periods of exacerbation and remission (99% suffer at least one relapse) 

• triggers of acute exacerbations are unknown but viral illnesses (EBV, adenovirus) may play a role 

• unable to predict the extent and severity of the disease over time (except those with ileocolitis have greater morbidity) thus while morbidity is very high, mortality is essentially zero