Ulcerative Colitis
Definition
- Idiopathic chronic inflammatory bowel disease primarily involving the mucosal layer of the large intestine
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)
Diagnostic Criteria
- The diagnosis of ulcerative colitis requires clinicopathologic correlation
- Inflammation is largely limited to mucosa and superficial submucosa
- Ulceration is generally shallow and does not extend into muscularis propria
- In fulminant colitis there may be destruction of the full mucosal and submucosal layers, and fissures and inflammation may involve the muscularis propria
- Lacks the fibrosis typical of Crohn disease
- May lead to toxic megacolon
- Neutrophilic infiltrate is present if disease is active
- Involves epithelium of surface and crypts
- Frequently forms crypt abscesses
- Chronic inflammatory infiltrate is present in the lamina propria and submucosa
- Lymphocytes, plasma cells, eosinophils
- Basal lymphoid aggregates may be present
- Granulomas are not seen
- Architectural changes characterized by crypt distortion are present in both active and inactive (quiescent) disease
- These findings are important as they demonstrate the chronic nature of the process
- Crypt / glandular abnormalities
- 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
- 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 nearly always involves a contiguous segment of colorectum
- Rectum is nearly always involved
- Therapeutic enemas may mask rectal disease
- Proximal extent is variable
- Disease limited to the rectum is termed ulcerative proctitis
- Patchy involvement and skip lesions are rare
- The appendix and appendiceal orifice may be involved in the absence of other right side disease and does not constitute grounds for changing the diagnosis
- Caution should be used in the diagnosis of cases with rectal sparing or skip lesions
- Terminal ileum may be involved in cases of pancolitis
- Termed “backwash ileitis”
- Nonspecific gastric abnormalities may be seen in patients with UC
(Lin)
- Most common is a focal lamina propria infiltrate of lymphocytes, neutrophils and histiocytes
- Diffuse chronic duodenitis is seen in a few cases
- Rectum is nearly always involved
- Paneth cell metaplasia may be prominent
- Paneth cells are rare in the normal left colon
- In extensively ulcerated cases, islands of residual inflamed mucosa are termed pseudopolyps
- Clinically and histopathologically intractable disease should prompt close inspection and immunohistologic staining for cytomegalovirus
- The presence of dysplasia predicts the development of colorectal carcinoma in ulcerative colitis
- 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"
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates: 11/11/09, 10/29/10
