Crohn Disease
Definition
- Idiopathic chronic inflammatory bowel disease characterized by transmural inflammation and patchy involvement
Alternate/Historical Names
- (Idiopathic) Inflammatory bowel disease encompasses both ulcerative colitis and Crohn disease and implies that other specific causes and diseases have been ruled out
- Regional enteritis
Diagnostic Criteria
- The diagnosis of Crohn disease requires clinicopathologic correlation
- Inflammation is transmural, from mucosa to serosa
- Lymphoid aggregates present at all levels
- Infiltrate in some cases is more prominent in submucosa and serosa, with relative sparing of muscularis propria
- Especially in early cases
- Serosal involvement leads to fat wrapping around the bowel
- Ulceration and fissures may extend into and through the muscularis propria
- Fistulas to other bowel loops, skin and other organs may form
- Intramural inflammatory infiltrate is largely lympho-histiocytic
- Neutrophils may be focally present
- Crypt abscesses may be present
- Granulomas are present in about 15-36% of biopsied cases
- Present in over half of colectomy specimens
- Compact aggregates of epithelioid histiocytes
- Non-necrotic
- Multinucleated giant cells may be present
- May be seen at all levels and in draining lymph nodes
- More common in children
- If present, acid fast and fungal stains should be performed to rule out infection
- Presence of granulomas does not indicate active disease
- Aphthous ulcers may be present in the intestine
- Erosion or ulcer abutting a mucosal or submucosal lymphoid aggregate
- Acute inflammation may be present in adjacent crypt lumens
- Architectural changes characterized by crypt distortion are present in both active and inactive (quiescent) disease
- Irregular, horizontal, dilated crypts
- Gland dropout is frequent
- Bifid, forked glands
- Shortened glands that fail to reach the muscularis mucosae
- Lamina propria fibrosis may be present
- Thickening of muscularis mucosae
- These findings are important as they demonstrate the chronic nature of the process
- Minimal architectural distortion may be seen in pediatric cases at initial presentation
- Complete resolution of architectural changes after a long period of disease inactivity is unusual but may be seen
- Process is usually discontinuous with patchy involvement and skip lesions
- It is important to biopsy normal appearing areas to rule out a contiguous segment of bowel that includes an area of quiescent colitis
- Process may involve the entire gastrointestinal tract
- Small intestine only - 30-50%
- Large intestine only – 25-30%
- Both small and large intestine – 30-50%
- Stomach or duodenum – 50% (typically mild)
- Anal fissures, fistulas and skin tags common, especially in children
- Esophagus and oral cavity - rare
- Paneth cell metaplasia may be prominent
- Paneth cells are rare in the normal left colon
- Neural hyperplasia may be present
- In submucosa and muscularis propria
- May contain ganglion cells
- Vascular changes are occasionally seen
- Non-inflammatory
- Intimal proliferation
- Fibrosis may occur at any level of the vessel wall
- Inflammatory
- Perivascular and intramural lymphoplasmacytic infiltrate
- Occasionally may include granulomas
- Distinguished from primary systemic vasculitis by the lack of extraintestinal involvement
- Clinically and histopathologically intractable disease should prompt close inspection and immunohistologic staining for cytomegalovirus
- Extensively ulcerated cases may develop toxic megacolon
- The presence of dysplasia predicts the development of colorectal carcinoma in Crohn disease
- Indeterminate colitis
- Diagnosis used for cases in which a definitive separation of ulcerative colitis and Crohn disease cannot be made
- May constitute up to 15% of cases
- Most are cases of fulminant colitis
- With long term follow-up, 80% of such cases are found to be ulcerative colitis
- This diagnosis should be reserved for resection specimens
- Endoscopic biopsy specimens that are not definitive may be designated as “Inflammatory Bowel Disease, Unclassified"
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting : November 11, 2009