Path Notes: Crohn's Disease*** Flashcards
What is Crohn’s disease?
Chronic, relapsing inflammatory bowel condition
CD may affect any portion of the GIT from oesophagus to anus, but most commonly affects distal SI and colon
Typically transmural
What is the typical extent/spread of CD?
Can affect any portion of the GIT from oesophagus to anus, but most commonly affects the terminal SI and colon
Typically transmural
SI involvement alone = 40%
SI and LI = 30%
LI alone = 30%
Epidemiology of CD
In western countries, incidence ranges from 3/100,000 to 4-10/100,000.
More common in females
Can occur at any age, but main peak is in 20s and 30s. Smaller peak in 60s and 70s
Smoking increases risk
What are the three key pathological features that characterise CD?
- Sharply demarcated and typically transmural involvement of bowel by inflammatory process with mucosal damage - skip lesions
- Presence of non-caseating granulomatas
- Fissuring, potentially with fistula formation
Describe the macroscopic features of CD regarding the serosa and intestinal wall/lumen
Serosa:
- Skip lesions
- Serosa becomes granular and grey
- Mesenteric fat often wraps around the bowel surface (creeping fat)
- Mesentery of the affection portion is typically thick, oedematous, and sometimes fibrotic
Intestinal wall: Is rubbery and thick due to the: 1. Oedema 2. Inflammation 3. Fibrosis 4. Hypertrophy of the muscularis propria
The intestinal lumen in nearly always narrowed - displays ‘string sign’ with barium contrast imaging
Describe the macroscopic features of CD regarding the mucosa
- Initially there is ulceration, oedema, and loss of normal mucosal texture
- With CD progression, the ulcerations tends to coalesce into long, serpentine ulcerative lines along the long axis of the GIT
- Intervening mucosa tends to be relatively spared (due to skip lesion habit)
- Development of cobblestone appearance
- Narrow fissures form between the folds of the mucosa. They can penetrate deeply through the wall, leading to bowel adhesions and serositis
- Extension of the fissures can lead to fistula formations, or sinus tracts formation to the skin
- Free perforation may occur
- Perforation and local abscesses can occur
Describe the microscopic appearance of CD
Mucosal Inflammation:
- Foci of neutrophil infiltrates into the epithelium, particularly overlying mucosal lymphoid aggregates
- Crypts regenerate and end up with bizarre branching shapes
Transmural inflammation affecting all layers:
- Chronic inflammatory cells suffuse the affected mucosa and, to a lesser degree, infiltrate the underlying tissue layers
- Lymphoid aggregates are usually found scattered throughout the bowel wall
Non-Caseating Granulomas:
- In 35% of cases, non-caseating granulomas may be present in all tissue layers of the bowel wall, in areas of active inflammation and in unaffected areas
What does the chronic mucosal damage (of CD) result in?
Within the SI - villus blunting
Within the LI - Irregular/branching crypts
- Crypt destruction leads to progressive atrophy
- Metaplasia, or the development of paneth cells in the distal colon (normally absent) - paneth cell metaplasia
- Reduplication of the muscularis mucosa
- Thickening irregularity
- Fibrosis of the submucosa
- May lead to strictures
Describe the clinical picture of CD:
- Intermittent attacks of diarrhoea
- Fever
- Abdo pain
- Attacks are often precipitated by stress
- Chronic blood loss may lead to anaemia
What are some complications of CD?
- Fibrosing strictures (narrowings)
- Fistulas (to adjacent sections of bowel/adjacent organs/to skin)
- Malabsorption (in terminal ileum CD) - chiefly B12, albumin, bile salts
- Anaemia (B12 or Fe deficiency)
- Increased risk of GIT cancer: those with longstanding CD have 5-6x increase (greater risk in UC)
What are the extra-intestinal manifestations of CD?
- Migratory Polyarthritis
- Sacroiliitis (inflammation of sacro-iliac joint)
- Ankylosing Spondylitis
- Erythema nodosum
- Clubbing
- Hepatic sclerosing cholangitis (has stronger affiliation with UC)
- Systemic Amyloidosis
