This review summarizes current diagnostic problems and advances with regard to patterns of
inflammation and dysplasia in
ulcerative colitis and
Crohn's disease.
Ulcerative colitis and
Crohn's disease have a variety of characteristic but non-specific pathologic features. In approximately 5% of
inflammatory bowel disease cases, a definite diagnosis of
ulcerative colitis or
Crohn's disease cannot be established, in which case the term "indeterminate"
colitis is used. Most cases of indeterminate
colitis are related to fulminant
colitis, a condition in which the classic features of
ulcerative colitis or
Crohn's disease may be obscured by severe ulceration with early superficial fissuring ulceration, transmural lymphoid aggregates, and relative rectal sparing. Approximately 20% of patients with indeterminate
colitis develop severe pouch complications, which is intermediate in frequency between
ulcerative colitis (8-10%) and
Crohn's disease (30-40%). In order to establish a diagnosis of
ulcerative colitis or
Crohn's disease, it is important to evaluate pathologic material in conjunction with clinical, laboratory, radiologic, and endoscopic features and to recognize the variety of changes that may be seen in fulminant
ulcerative colitis. There are a number of exceptions to the classic principles of
inflammatory bowel disease pathology that may lead to diagnostic
confusion. For instance, apparent skip lesions on biopsy analysis may occur in patients with
ulcerative colitis in the following settings; long term oral or topical
therapy, focal ascending colon, cecum and/or appendiceal involvement in patients with left sided
ulcerative colitis, upper gastrointestinal involvement in patients with
ulcerative colitis, and at initial presentation of
ulcerative colitis in pediatric patients. In all of these circumstances, the finding of patchy disease and/or rectal sparing should not be misinterpreted as either evidence against a diagnosis of
ulcerative colitis, or as representing skip areas characteristic of
Crohn's disease. Patients with
ulcerative colitis and
Crohn's disease are at increased risk for the development of dysplasia and
carcinoma. Recent studies suggest that given a similar duration and extent of disease, patients with
Crohn's disease have a similar risk of dysplasia and
cancer as patients with
ulcerative colitis. Dysplasia in
ulcerative colitis may be classified as flat or elevated (dysplasia associated lesion or mass [
DALM]). Patients with flat high grade dysplasia are generally treated with
colectomy. However, there is recent evidence to suggest that patients with flat low grade dysplasia, particularly if detected at the time of initial endoscopic exam, or if its multifocal or synchronous, should also be treated with
colectomy. Elevated lesions in
ulcerative colitis (
DALM) are subdivided into "
adenoma-like" and "non-
adenoma-like" lesions based on their endoscopic appearance. Recent data suggests that
adenoma-like lesions, regardless of the grade of dysplasia, or the location of the lesion (i.e., inside or outside areas of established
colitis) may be treated adequately by polypectomy if there are no other areas of flat dysplasia in the patient. Although there are some histologic and molecular features that can help differentiate sporadic
adenomas from
adenoma-like polypoid dysplastic lesions related to
ulcerative colitis, none of these adjunctive techniques can help distinguish these lesions definitively in any single patient. Patients with a non-
adenoma-like
DALM, (irregular, broad based, or strictured lesion) should be treated with
colectomy because of the high probability of
adenocarcinoma. The surveillance and treatment options for patients with flat and elevated dysplasia in
ulcerative colitis are reviewed in detail.