Diagnostic difficulties in inflammatory bowel disease pathology

Abstract

This review summarizes some of the common diagnostic problems encountered by pathologists when evaluating patients with chronic colitis and in whom inflammatory bowel disease (IBD) is either suspected or within the differential diagnosis. Both ulcerative colitis (UC) and Crohn's disease (CD) show characteristic, but non-specific, pathological features that may overlap and result in a diagnosis of 'indeterminate colitis' (IC). However, other reasons why pathologists may entertain a diagnosis of IC include failure to recognize or accept certain 'hardcore' histological features as indicative of CD, an attempt to classify cases of chronic colitis based on mucosal biopsy material or in the absence of adequate clinical and radiographic information, and the presence of other disease processes that mask, or mimic, IBD. In addition, some cases of UC may show unusual CD-like features, such as discontinuous or patchy disease, ileal inflammation, extracolonic inflammation, granulomatous inflammation in response to ruptured crypts, aphthous ulcers, or transmural inflammation. Furthermore, other forms of colitis, such as microscopic colitis, diverticulitis and diversion colitis may, on occasion, also show IBD-like changes. The clinical and pathological features that aid in the distinction between these entities, and others, are covered in detail in this review.

A contemporary and critical appraisal of ‘indeterminate colitis‘

“…1 In certain circumstances, particularly when there are overlapping clinical features, it becomes incumbent on the pathologist to help establish a definitive diagnosis of either UC or CD (or other types of IBD) in resection specimens. 2,3 In most instances, these two disorders may be readily distinguished from each other, particularly when each exhibits classic gross and microscopic features (Table 1). 3 Unfortunately, some patients with IBD show overlapping pathologic features of UC and CD, which makes definite distinction between these two disorders difficult, or even impossible.…”

“…2,3 In most instances, these two disorders may be readily distinguished from each other, particularly when each exhibits classic gross and microscopic features (Table 1). 3 Unfortunately, some patients with IBD show overlapping pathologic features of UC and CD, which makes definite distinction between these two disorders difficult, or even impossible. When a pathologist cannot make a definite diagnosis of UC or CD (or any of the other type of IBD that mimics UC or CD), a diagnosis of 'indeterminate colitis' (IC) is often rendered.…”

“…When a pathologist cannot make a definite diagnosis of UC or CD (or any of the other type of IBD that mimics UC or CD), a diagnosis of 'indeterminate colitis' (IC) is often rendered. 3 Some of the other terms that are used in this setting include 'uncertain colitis,' 'idiopathic chronic colitis,' 'IBD-unclassified,' 'IBD-nos' and 'IBD-unknown etiology'. 1,4 In 2005, an international working party of IBD physicians indicated a preference for the term 'IBD unclassified' for patients with chronic colitis (IBD) without definitive features of UC or CD.…”

“…3,5 Previously reported rates of diagnosis range from 1 to 20% of IBD cases. 3,5 The frequency of establishing this diagnosis is often related to the level of awareness of the broad spectrum of pathologic features that may occur in UC and CD (see below section on causes of uncertainty in IBD pathology).…”

“…3,5 Previously reported rates of diagnosis range from 1 to 20% of IBD cases. 3,5 The frequency of establishing this diagnosis is often related to the level of awareness of the broad spectrum of pathologic features that may occur in UC and CD (see below section on causes of uncertainty in IBD pathology). For instance, in a study by Farmer et al, 6 24 university medical center pathologists from 8 institutions evaluated 84 colectomy specimens and 35 sets of biopsies from 119 consecutive patients with colonic IBD.…”