Problem areas in the pathology of chronic inflammatory bowel disease

The differential diagnosis of chronic inflammatory bowel disease (CIBD) remains one of the most demanding conundra in gastrointestinal pathological practice. It may be difficult to make a definitive diagnosis of CIBD in the acute setting and important infective causes should always be excluded by histopathological, histochemical or microbiological means. Although granulomas are often regarded as virtually diagnostic of Crohn's disease (CD), there are many other, notably infective, causes that may give rise to granulomas and cause diagnostic uncertainty. To confound matters, a definitive diagnosis of either CD or ulcerative colitis (UC) may not be possible in a relatively large number of cases on biopsy, and even at resection, between 10% and 20% will be designated as ‘indeterminate colitis’. This is an important concept that has specific influence on management. CIBD may be causally related to diverticulosis, although mimicry of CIBD by diverticulitis and diverticular colitis is much more likely. The identification of low-grade dysplasia in UC is associated with poor reproducibility; fortunately, recent studies have shifted the emphasis from surgical treatment of dysplasia to endoscopic surveillance and local treatment. There is increasing interest in the histopathological presentation of CIBD in the upper gut. The predictability of focal active gastritis/focally enhanced gastritis for a diagnosis of CD has been recently questioned, and, as always, the context in which pathological features are found is much more important. The vigilant histopathologist is always cautious before making any diagnosis in CIBD pathology without due consideration of the clinical and endoscopic context.