Page 424 - Concise Pathology for Exam Preparation ( PDFDrive )

14 The Oral Cavity and Gastrointestinal Tract 409

Microscopy

• Active Crohn disease shows abundant neutrophils in the lamina propria and crypts
which damage the crypt epithelium and form crypt abscesses. Ulceration is fre-
quent.
• Repeated cycles of crypt damage and regeneration lead to architectural distortion of the
mucosa. Branching crypts with abnormal shapes replace the normally straight and par-
allel crypts.
• Transmural inflammation affecting all layers can be demonstrated.
• Noncaseating granulomas and fibrosis are common. Granulomas can also be seen in the
mesenteric lymph nodes. Cutaneous nodules form which also show noncaseating
granulomas (earlier labelled metastatic Crohn disease).

Q. Describe the clinical features, morphology and complications of
ulcerative colitis.

Ans. Ulcerative colitis is an ulceroinflammatory disease limited to colon. It usually affects
only the mucosa and submucosa except in very severe forms. It peaks between 20 and
25 years and is more common in females.
Gross Morphology

• The lesion extends in a retrograde and continuous fashion from rectum to proximal
parts of colon; no skip lesions are seen. Involvement of a few centimetres of ileum
when the entire colon is involved can be seen and is termed ‘backwash ileitis’.
• The mucosa is red, granular and friable mucosa which bleeds easily
• Broad-based mucosal ulcers; aligned along the long axis of the colon and pseudopolyps
(due to bulging of regenerating mucosa) are a common sight
• No mural thickening is seen the serosa is normal

Microscopy
• Mucosal inflammation, chronic mucosal damage and ulceration (ulcer limited to
mucosa and submucosa)
• A diffuse, predominantly mononuclear infiltrate in lamina propria
• Crypt abscesses (due to neutrophilic infiltration of crypts in active stage)
• Even after healing, mucosal architectural disarray, colonic gland atrophy and submucosal
fibrosis may be seen.
• Epithelial dysplasia is common.

Complications
• Toxic megacolon (caused by neuromuscular shutdown due to damage to muscularis
propria and neural plexus)
• Perianal fistula
• Development of colonic carcinoma
• Bleeding
• Perforation (damage to muscularis propria leads to perforation and pericolonic abscess
formation)

Q. Differentiate between Crohn disease and ulcerative colitis.
Ans. Differences between Crohn disease and ulcerative colitis are summarized in the
Table 14.6.

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