Histological Assessment of Disease Activity in UC
Histological Assessment of Disease Activity in UC
Recommendations for the technical approach to biopsy specimens are summarised in Table 6. Technical procedures for histological assessment of UC are not been well studied. The sites and the number of biopsy specimens have not been clearly defined for the assessment of histological Mucosal Healing but patients with atypical distribution of lesions such as a caecal patch, peri-appendiceal inflammation associated with a left-sided colitis are seen in UC and in approximately 10–20% of UC patients the inflammation may extend into the terminal ileum (backwash-ileitis). When present, lesions in the proximal large bowel need to be deliberately biopsied and may be the site of maximum inflammation.
Treatment may change the classical distribution pattern of the inflammation. Patchiness, rectal sparing up to normalisation of the mucosa can be observed. Correlation of pre- and post-treatment disease activity stratified to location (e.g. rectum, sigmoid colon, etc.) will be critical for accurate comparison. In the study by Kleer et al., 65% of the endoscopic and histological findings were comparable, whereas in 25% a chronic colitis was diagnosed in biopsies from an endoscopically normal looking mucosa. In 10% the opposite was seen. It is also likely that numerous biopsy specimens made in different locations could improve MH histological assessment. Normal and abnormal mucosa (as ulcers) should be analysed. It is unclear whether extent of disease as assessed by evaluation of numerous segments, is better than simply evaluating the most affected (endoscopically abnormal) part of the bowel. In the first scenario, we suggest two biopsies for each site (minimum five sites – right colon, transverse, descending, sigmoid and rectum, to which can be added both flexures and the caecal pole). Biopsy specimens have to be made in abnormal areas. A basic minimum series at flexible sigmoidoscopy should include biopsies from the descending colon, sigmoid and rectum, ensuring that the most severe area is also included, especially if not in this series of biopsies. Inflammatory (pseudo) polyps should be avoided unless there is a possibility of these being dysplastic, but should not form part of the series being used for assessment.
The diagnostic yield increases with the number of evaluable sections examined. Evaluable means that they are correctly oriented so that both the surface and bases of the mucosa is in the section – i.e. sections are well oriented. The primary determinant of ability to orientate biopsies is its size. Size is maximised by using large cup/capacity forceps at least 3.2 mm, which fit into a standard 2.8 mm biopsy channel. Biopsies that are small (<4 mm) become increasingly difficult to orientate, whether carried out in the endoscopy suite using a mounting medium for biopsies (e.g. Millipore filter) all need to be orientated on edge in the laboratory. This allows the mucosal and submucosal surfaces to be identified when sectioned, which in turn allows both the surface and basal regions to be evaluated.
The ideal number of sections to be examined in routine practice has not been established. In routine practice, step sections (a series on one slide followed by discarding several sections and then cutting some more for the next slide) is simplest. Sections should be 3–5 μmol/L thick. It is fundamental that knives used for sectioning should be sharp or new to avoid 'chatter' and other artefacts, and that the sections need to be cut with care by technologists adept at cutting excellent section to allow the accurate identification of all cells present.
Endoscopic biopsies should be immediately fixed in buffered formalin. Biopsies from each region of the bowel (see previous discussion) should be put into separate vials as is essential to map and grade the histological distribution and degree of inflammation in different colonic segments. This allows a better assessment of the distribution of architectural abnormalities, surface abnormalities and basal plasmacytosis, which can be very difficult in case of not well-oriented sample. In case of poor quality of sample, the pathologist has to mention it in his report.
Routine staining with hematoxylin and eosin is appropriate for diagnosis. Special stains, such as immunohistochemistry or other techniques for histological MH assessment are not needed routinely. The assessment of myeloperoxidase by immunochemistry is not required, because neutrophils are easily detectable with routine staining.
There is no validated scoring system. We cannot make recommendations for a preferable scoring system. Pathologist has to mention in his report some histological features to define the severity of disease as acute inflammatory infiltrate, chronic inflammatory infiltrate, ulcers and architectural abnormalities.
Examining biopsies for CMV (Cytomegalovirus) reactivation on colonic biopsy should be performed in all patients with severe colitis and especially in biopsies with prominent granulation tissue. Semiquantitative immunohistochemistry, reporting the number of infected cells and/or the number of CMV positive biopsy fragments, may have a predictive value. Recently, our group showed that the correlation between available indexes is strong. Intraobserver reproducibility and interobserver agreement for all indexes is very good. Histological items that showed the best interobserver agreement are 'erosion/ulcers' and 'acute inflammatory cells infiltrate/neutrophils in lamina propria'.
Technical Approach for Obtaining Optimal Biopsy Specimens for Histological Assessment
Recommendations for the technical approach to biopsy specimens are summarised in Table 6. Technical procedures for histological assessment of UC are not been well studied. The sites and the number of biopsy specimens have not been clearly defined for the assessment of histological Mucosal Healing but patients with atypical distribution of lesions such as a caecal patch, peri-appendiceal inflammation associated with a left-sided colitis are seen in UC and in approximately 10–20% of UC patients the inflammation may extend into the terminal ileum (backwash-ileitis). When present, lesions in the proximal large bowel need to be deliberately biopsied and may be the site of maximum inflammation.
Treatment may change the classical distribution pattern of the inflammation. Patchiness, rectal sparing up to normalisation of the mucosa can be observed. Correlation of pre- and post-treatment disease activity stratified to location (e.g. rectum, sigmoid colon, etc.) will be critical for accurate comparison. In the study by Kleer et al., 65% of the endoscopic and histological findings were comparable, whereas in 25% a chronic colitis was diagnosed in biopsies from an endoscopically normal looking mucosa. In 10% the opposite was seen. It is also likely that numerous biopsy specimens made in different locations could improve MH histological assessment. Normal and abnormal mucosa (as ulcers) should be analysed. It is unclear whether extent of disease as assessed by evaluation of numerous segments, is better than simply evaluating the most affected (endoscopically abnormal) part of the bowel. In the first scenario, we suggest two biopsies for each site (minimum five sites – right colon, transverse, descending, sigmoid and rectum, to which can be added both flexures and the caecal pole). Biopsy specimens have to be made in abnormal areas. A basic minimum series at flexible sigmoidoscopy should include biopsies from the descending colon, sigmoid and rectum, ensuring that the most severe area is also included, especially if not in this series of biopsies. Inflammatory (pseudo) polyps should be avoided unless there is a possibility of these being dysplastic, but should not form part of the series being used for assessment.
The diagnostic yield increases with the number of evaluable sections examined. Evaluable means that they are correctly oriented so that both the surface and bases of the mucosa is in the section – i.e. sections are well oriented. The primary determinant of ability to orientate biopsies is its size. Size is maximised by using large cup/capacity forceps at least 3.2 mm, which fit into a standard 2.8 mm biopsy channel. Biopsies that are small (<4 mm) become increasingly difficult to orientate, whether carried out in the endoscopy suite using a mounting medium for biopsies (e.g. Millipore filter) all need to be orientated on edge in the laboratory. This allows the mucosal and submucosal surfaces to be identified when sectioned, which in turn allows both the surface and basal regions to be evaluated.
The ideal number of sections to be examined in routine practice has not been established. In routine practice, step sections (a series on one slide followed by discarding several sections and then cutting some more for the next slide) is simplest. Sections should be 3–5 μmol/L thick. It is fundamental that knives used for sectioning should be sharp or new to avoid 'chatter' and other artefacts, and that the sections need to be cut with care by technologists adept at cutting excellent section to allow the accurate identification of all cells present.
Endoscopic biopsies should be immediately fixed in buffered formalin. Biopsies from each region of the bowel (see previous discussion) should be put into separate vials as is essential to map and grade the histological distribution and degree of inflammation in different colonic segments. This allows a better assessment of the distribution of architectural abnormalities, surface abnormalities and basal plasmacytosis, which can be very difficult in case of not well-oriented sample. In case of poor quality of sample, the pathologist has to mention it in his report.
Routine staining with hematoxylin and eosin is appropriate for diagnosis. Special stains, such as immunohistochemistry or other techniques for histological MH assessment are not needed routinely. The assessment of myeloperoxidase by immunochemistry is not required, because neutrophils are easily detectable with routine staining.
There is no validated scoring system. We cannot make recommendations for a preferable scoring system. Pathologist has to mention in his report some histological features to define the severity of disease as acute inflammatory infiltrate, chronic inflammatory infiltrate, ulcers and architectural abnormalities.
Examining biopsies for CMV (Cytomegalovirus) reactivation on colonic biopsy should be performed in all patients with severe colitis and especially in biopsies with prominent granulation tissue. Semiquantitative immunohistochemistry, reporting the number of infected cells and/or the number of CMV positive biopsy fragments, may have a predictive value. Recently, our group showed that the correlation between available indexes is strong. Intraobserver reproducibility and interobserver agreement for all indexes is very good. Histological items that showed the best interobserver agreement are 'erosion/ulcers' and 'acute inflammatory cells infiltrate/neutrophils in lamina propria'.
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