Histopathology of IBD Colitis. A practical approach from the pathologists of the Italian Group for the study of the gastrointestinal tract (GIPAD)

Abstract

Summary Inflammatory bowel diseases (IBDs) are lifelong disorders in which an interaction between genetic and environmental factors is involved. IBDs include two entities: Crohn’s disease (CD) and ulcerative colitis (UC); these can be adequately diagnosed and distinguished with a correct methodological approach based on communicating exhaustive clinical, endoscopic and laboratory information to the pathologist and performing adequate bioptic sampling and precise morphological signs including crypt architecture, distribution of inflammation and granulomas, when present. IBD needs to be distinguished from non-IBD colitis, mostly at its onset. Moreover, IBDs are associated with an increased risk of developing colorectal adenocarcinoma. In daily pathological practice, correct diagnosis of IBD and its subclassification as well as a correct detection of dysplasia is imperative to establish the best therapeutic approach.

Very Early Onset-IBD: evidence for the need of a multidisciplinary approach

“…All the different segments of the ileo-colic tract should be extensively sampled, regardless of the endoscopic extension of the disease, with at least two biopsies in the terminal ileum and in each segment of the large bowel (caecum, ascending, transverse, descending, sigmoid colon and rectum), even if the mucosa appears endoscopically normal. At the time of the first diagnosis, and for a comprehensive evaluation, esophageal, gastric and duodenal biopsies are recommended 6 .…”

“…Extensive mucosal sampling of both upper and lower GI mucosae is imperative to reduce the differential diagnosis landscape. Duodenal biopsies, including the first (duodenal bulb) and second parts of the duodenum, and multiple colonic biopsies from different sites, including the terminal ileum, should be taken and sent for pathologic examination in separately coded vials 6 .…”

“…I ) 4 . Underlying monogenic disorders are more represented in VEO-IBD compared with ‘pure’ IBD diagnosed at older age; thus, a subset of patients presents with a more severe and heterogeneous phenotype than older onset IBD 6 . The monogenic etiologies of VEO-IBD identified to date can be divided into six main (and sometimes overlapping) categories: (i) general immune dysregulation, (ii) T and B cell defects, (iii) phagocytic defects, (iv) hyper- and auto-inflammatory conditions, (v) epithelial barrier dysfunction, and (vi) other conditions 3 .…”

Histopathology of Non-IBD Colitis. A practical approach from the Italian Group for the study of the gastrointestinal tract (GIPAD)

“…1E ) 9 . It is important to remember that CMV colitis can complicate IBD and make its recognition difficult, and that quantification is crucial for establishing the correct therapy 3 . More specific, or even diagnostic, morphological patterns are characterized by granulomatous inflammation: PAS-positive schistosomal eggs, at times calcified, are contained in microgranulomas associated to fibrotic submucosal thickening and lymphoid hyperplasia 10 .…”

“…Below the histopathological features of the most frequent NIBDCs are summarized. The main differential diagnosis is with IBD, especially at the onset stage of IBD, for the characterization of which we refer to ‘IBD-colitides’ in this special issue of Pathologica 3 .…”