Unambiguous interpretation of colorectal biopsy specimens is important for clinical decisions in the investigation of suspected chronic idiopathic inflammatory bowel disease (IBD). Variability of reporting style and terms such as mild inflammatory change and non-specific proctitis/colitis may hide pathologists’ difficulties with diagnostic uncertainty and confuse clinical management. Four main problems underlie these difficulties:

  1. lack of awareness of the range of normal colorectal histology and the minimal features which indicate clinically important inflammation;
  2. wide overlap in the pathological changes of most large bowel inflammatory diseases;
  3. lack of awareness of the accuracy and reproducibility of many changes used in diagnosis; and
  4. absence of standard terminology for pathological description and diagnosis.

On behalf of the British Society of Gastroenterology, we have used an evidencebased approach to compile guidelines for the biopsy diagnosis of suspected chronic idiopathic IBD.

The guidelines are aimed primarily at improved accuracy of diagnosis when colorectal biopsy is used in the initial investigation of patients with diarrhoea. The objectives are to assist: the recognition of normal colorectal mucosa; the detection of important minor inflammatory change needing further investigation; the early diagnosis of chronic idiopathic IBD; the distinction between ulcerative colitis and Crohn’s disease; the recognition of infective type colitis; and the diagnosis of less frequent forms of colitis. The guidelines include recommendations for minimum clinical information, useful morphological features, standardised terminology, and a clinically relevant reporting format. The evidence is from Europe and North America, and the conclusions should not be applied uncritically where the prevalence and the nature of the diseases are very different.

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