For a reliable diagnosis of inflammatory bowel disease, ileocolonoscopy rather than rectoscopy should be performed. A minimum of two biopsies from at least five sites along the colon, including the rectum, and the terminal ileum should be obtained [EL 1]. In patients with fulminant colitis, two samples from at least one site should be obtained [EL5]. The biopsies should be collected in separate vials, as localization of the biopsies gives important diagnostic information

All tissue samples should be fixed immediately by immersion in buffered formalin or an equivalent solution prior to transport [EL5]. Since lesions may be focal, it is recommended that multiple sections from each sample are examined [EL2]

The biopsy samples should be accompanied by clinical information including endoscopic findings as well as the age of the patient, duration of disease, duration and type of treatment, comorbidities and travel history [El 5]

A surgical sample needs complete gross examination, carried out in an orderly and systematic manner, including photographic documentation, preferably at the time when the specimen is removed [EL5]

The pathology report in all chronic colitides should give an indication of the activity of the disease. Particularly in Crohn's disease, inactivity in the biopsy may not reflect inactivity of the disease [EL5]

Focal (discontinuous) chronic inflammation, focal crypt irregularity (discontinuous crypt distortion) and granulomas (not related to crypt injury) are the generally accepted microscopic features which allow a diagnosis of CD in the colon (on endoscopic biopsies) [EL2]. The same features and, in addition, an irregular villous architecture, can be used for analysis of endoscopic biopsy samples from the ileum. If the ileitis is in continuity with colitis, the diagnostic value of this feature should be used with caution [EL2]

Despite detailed histologic criteria used to differentiate Crohn's colitis from ulcerative colitis in colonoscopic biopsies, accurate discrimination between the two diseases is not yet optimal among expert gastrointestinal pathologists [EL 2]

A surgical sample needs a complete gross examination, carried out in an orderly and systematic manner, including photographic documentation, preferably at the time when the specimen is removed [EL5, RG D]. Once gross observations are completed, the sample is opened along its longitudinal axis (along the antimesenteric or antimesocolic border, except perhaps at the sites of any carcinoma, where it may be preferable to leave that small segment unopened during fixation) and specimens for microscopy are collected, including the lymph nodes, terminal ileum and appendix [EL2, RG B].

The optimum number of samples from a colectomy specimen that should be obtained has not been established. However, multiple samples will improve the diagnostic yield. It is a mistake to sample only visible lesions. The samples can be processed routinely [EL5, RG D].

At onset, CD in children is associated with more colitis and less ileitis.The frequency of granulomas is higher in children than in adults. Focal inflammation in the upper gastrointestinal tract is of assistance in differentiating CD from UC [EL 2]

For a reliable diagnosis of inflammatory bowel disease, ileocolonoscopy rather than rectoscopy should be performed. A minimum of two biopsies from at least five sites along the colon, including the rectum, and the terminal ileum should be obtained [EL 1]. In patients with fulminant colitis, two samples from at least one site should be obtained [EL5]. The biopsies should be collected in separate vials, as localization of the biopsies gives important diagnostic information

All tissue samples should be fixed immediately by immersion in buffered formalin or an equivalent solution prior to transport [EL5]. Since lesions may be focal, it is recommended that multiple sections from each sample are examined [EL2]

The biopsy samples should be accompanied by clinical information including endoscopic findings as well as the age of the patient, duration of disease, duration and type of treatment, comorbidities and travel history [El 5]

A surgical sample needs complete gross examination, carried out in an orderly and systematic manner, including photographic documentation, preferably at the time when the specimen is removed [EL5]

The pathology report in all chronic colitides should give an indication of the activity of the disease. Particularly in Crohn's disease, inactivity in the biopsy may not reflect inactivity of the disease [EL5]

For a reliable diagnosis of ulcerative colitis, a minimum of two biopsies from at least five sites around the colon [including the rectum] and the ileum should be obtained [EL 2]

Microscopic diagnosis of ulcerative colitis is based on widespread crypt architectural distortion, a diffuse transmucosal inflammatory infiltrate with basal plasmacytosis, eventually associated with an active component, causing cryptitis and crypt abscesses. Mucin depletion is less specific, but a helpful diagnostic feature [EL 1]

Basal plasmacytosis is the earliest diagnostic feature with the highest predictive value for the diagnosis of ulcerative colitis [EL3]. Preserved crypt architecture and the absence of a transmucosal inflammatory cell infiltrate do not rule out ulcerative colitis at an early stage. Therefore, repeat biopsies are recommended not sooner than 6 weeks after the initial assessment for the diagnosis of ulcerative colitis [EL3]

The diagnosis of long-standing disease is based on the widespread crypt architectural distortion and the presence of a diffuse increased transmucosal inflammatory cell infiltrate [EL 1]. In this situation the mucosal histology can be associated with someatypical features such as normal mucosa, discontinuous inflammation and rectal sparing. Awareness of these morphologic features is important toavoid misdiagnosis, inp articular change of diagnosis to Crohn's disease [EL3]

In quiescent disease, the mucosa in ulcerative colitis may show some features related to architectural damage and recovery, such as architectural crypt distortion (atrophy and branching) as well as epithelial regeneration, disappearance of basal plasmacytosis and increased transmucosal cellularity. Active inflammation is usually not observed [EL3]

Histologic findings predictive of ensuing clinical relapse in patients with quiescent ulcerative colitis are basal plasmacytosis, increased transmucosal cellularity, high number of neutrophils and eosinophils, crypt abscesses, mucin depletion and damage of the surface epithelium [EL4]

Treatment may change the classical distribution pattern of the inflammation. Patchiness, rectal sparing up to normalization of the mucosa can be observed. Awareness of these treatment-related effects is important in the evaluation of biopsies from treated patients to avoid misdiagnosis [EL3]. The pathology report should give an indication of the activity of the disease [EL5]

Testing for CMV reactivation on colonic biopsy should be performed in all patients with severe colitis refractory to immunosuppressive therapy. In addition, testing should be performed in biopsies with prominent granulation tissue derived from large ulcers [EL2]. Semiquantitative immunohistochemistry, reporting the number of infected cells and/or the number of CMV positive biopsy fragments, may have a predictive value. Testing in other groups should be on a case by case basis [EL5]

Classically, macroscopic examination of a resection specimen may show a continuous inflammatory process, beginning from the rectum and extending proximally. Awareness of unusual macroscopic distribution patterns, such as the cecal patch, rectal sparing and backwash ileitis is important to avoid wrong subtyping of the inflammatory bowel disease [EL3]

In comparison with adults, a higher proportion of children with UC presents initially with subtotal or with extensive colitis [EL2]. As in adults, the presence of backwash ileitis does not exclude a diagnosis of UC. The prevalence of backwash ileitis seems to be similar in children and adults [EL3]. Periappendiceal inflammation, without more extensive and significant cecal inflammation, is frequently seen in UC. Such inflammation should not be regarded as supportive evidence for the diagnosis of CD [EL 3]. In young children with aberrant presentation of disease, ulcerative colitis should always be considered in the differential diagnosis even if histology is not typical [EL1]

Dysplasia (intrepithelial neoplasia) represents the best and most reliable marker of malignancy risk in patients with ulcerative colitis. Colitis-associated dysplasia develops only in areas with chronic inflammation and can be divided into 4 morphologic categories: negative (regenerating epithelium), indefinite and positive for low-grade dysplasia and high-grade dysplasia [EL 2]. Inter-observer agreement is poor for low-grade and indefinite dysplasia. Confirmation of dysplasia by an independent expert GI pathologist is recommended [EL 2]

Colitis-associated dysplasia consists of flat and elevated lesions. Elevated lesions request sampling of the surrounding and remote mucosa for diagnosis and treatment decision [EL 2]

For surveillance 4 biopsy specimens should be taken from every 10 cm of the entire colon in addition to biopsies from macroscopically visible atypical lesions [EL 2]

Adenoma-like lesions (sporadic adenomas) may be difficult to distinguish from colitis-associated dysplasia. The distinction is however important, because the management of sporadic adenomas differs from that of colitis-associated dysplasia. The patient's age, the site and morphology (endoscopic appearance, microscopy) of the lesion, along with biopsies of flat surrounding mucosa, may be helpful in this distinction [EL2]

For a proper histologic evaluation of pouchitis multiple biopsies are recommended. The exact location has not been determined but according to some data it is useful to take biopsies from the anterior and posterior wall avoiding suture lines. Samples from the posterior wall are more likely to show the inflammatory changes [EL 2]