Lower GI Endoscopy: Guidance on Indications for Biopsy
Lower GI Endoscopy: Guidance on Indications for Biopsy
The key reasons for performing biopsies in patients with suspected active ulcerative colitis are to help confirm the diagnosis and to determine the extent of the disease. Knowledge of the latter is important for determining the best management strategy. Biopsies from patients with active ulcerative colitis may show characteristic histopathological features, but these are rarely specific for the condition. For example, biopsies in early IBD—before the microscopic features of disease chronicity have had chance to develop—may show features that are essentially indistinguishable from those of self-limiting colitis (infective). Therefore, the clinical history and endoscopic appearance are important—the histopathologist may be willing to consider a diagnosis of early IBD in the differential diagnosis if the history is known to be short, when the absence of features of chronicity might otherwise suggest that IBD is unlikely. Opportunistic infections can be important to identify, whether they are the primary diagnosis or a secondary cause of relapse in IBD. Conditions such as tuberculosis and lymphogranuloma venereum are important differential diagnoses of IBD, especially Crohn's disease. Immunohistochemistry can be used to highlight and positively identify inclusion bodies (eg, for cytomegalovirus) and additional tests—for example, PCR-based tests—can be obtained where required (eg, for cytomegalovirus or Chlamydia trachomatis).
Biopsies from a colonic segment affected by diverticulosis may show overlying mucosal inflammation that can mimic either ulcerative colitis or Crohn's disease—the characteristics of chronic inflammation and/or other features commonly seen in Crohn's disease—for example, granulomas, may be present. Therefore, if a segmental colitis is encountered (figure 1), it is important to take biopsies from both the inflamed segment and a non-inflamed segment—for example, the rectum—to distinguish so-called diverticular colitis from chronic ulcerative colitis. Terminal ileal biopsy may provide useful additional information (eg, the presence of granulomas or ulcer-associated cell lineage) in patients where there is significant clinical suspicion of Crohn's disease.
Ischaemic colitis can also be confused with IBD. The clinical picture of an elderly patient with known arterial disease, with hypotension or after major vascular surgery, increases the suspicion. The endoscopic changes can mimic IBD but a sharply demarcated disease distribution relating to the anatomy of the arterial supply may be a useful feature. Colonic biopsies in cases of subacute ischaemia may have a similar appearance to those of Crohn's disease, but features characteristic of subacute ischaemia—for example, variable degrees of lamina propria fibrosis (also seen in chronic ischaemia), haemosiderin deposition, capillary ectasia and microthrombi—may also be present.
When mapping the extent of active ulcerative colitis, multiple colonic biopsies from the proximal colon to rectum are recommended and should be labelled according to their site of origin. Knowledge of the extent of disease is important for determining treatment, so a minimum of five to six biopsies covering different segments of the large intestine is required. Ulcerative colitis is described classically as always involving the rectum and extending for a variable distance into the proximal colon, but in some cases this distribution is not seen. Waxing and waning of the disease and the effect of partial treatment may result in sparing of the rectum and/or disease that shows a patchy distribution on endoscopic and/or histopathological examination. Furthermore, it is possible that the degree of inflammation assessed endoscopically may not completely correlate with the presence of inflammation within corresponding mucosal biopsies. In a patient in whom there is an otherwise confident diagnosis of ulcerative colitis, the presence of these features alone should not result in a change of diagnosis from ulcerative colitis to Crohn's disease. It is also entirely possible for mucosal biopsies from patients with quiescent IBD to have a histopathological appearance that is indistinguishable from normal. Therefore, the presence of microscopically normal colorectal mucosa does not preclude a diagnosis of previously active IBD.
What Is the Optimal Biopsy Technique for Patients With Active Ulcerative Colitis?
The key reasons for performing biopsies in patients with suspected active ulcerative colitis are to help confirm the diagnosis and to determine the extent of the disease. Knowledge of the latter is important for determining the best management strategy. Biopsies from patients with active ulcerative colitis may show characteristic histopathological features, but these are rarely specific for the condition. For example, biopsies in early IBD—before the microscopic features of disease chronicity have had chance to develop—may show features that are essentially indistinguishable from those of self-limiting colitis (infective). Therefore, the clinical history and endoscopic appearance are important—the histopathologist may be willing to consider a diagnosis of early IBD in the differential diagnosis if the history is known to be short, when the absence of features of chronicity might otherwise suggest that IBD is unlikely. Opportunistic infections can be important to identify, whether they are the primary diagnosis or a secondary cause of relapse in IBD. Conditions such as tuberculosis and lymphogranuloma venereum are important differential diagnoses of IBD, especially Crohn's disease. Immunohistochemistry can be used to highlight and positively identify inclusion bodies (eg, for cytomegalovirus) and additional tests—for example, PCR-based tests—can be obtained where required (eg, for cytomegalovirus or Chlamydia trachomatis).
Biopsies from a colonic segment affected by diverticulosis may show overlying mucosal inflammation that can mimic either ulcerative colitis or Crohn's disease—the characteristics of chronic inflammation and/or other features commonly seen in Crohn's disease—for example, granulomas, may be present. Therefore, if a segmental colitis is encountered (figure 1), it is important to take biopsies from both the inflamed segment and a non-inflamed segment—for example, the rectum—to distinguish so-called diverticular colitis from chronic ulcerative colitis. Terminal ileal biopsy may provide useful additional information (eg, the presence of granulomas or ulcer-associated cell lineage) in patients where there is significant clinical suspicion of Crohn's disease.
Ischaemic colitis can also be confused with IBD. The clinical picture of an elderly patient with known arterial disease, with hypotension or after major vascular surgery, increases the suspicion. The endoscopic changes can mimic IBD but a sharply demarcated disease distribution relating to the anatomy of the arterial supply may be a useful feature. Colonic biopsies in cases of subacute ischaemia may have a similar appearance to those of Crohn's disease, but features characteristic of subacute ischaemia—for example, variable degrees of lamina propria fibrosis (also seen in chronic ischaemia), haemosiderin deposition, capillary ectasia and microthrombi—may also be present.
When mapping the extent of active ulcerative colitis, multiple colonic biopsies from the proximal colon to rectum are recommended and should be labelled according to their site of origin. Knowledge of the extent of disease is important for determining treatment, so a minimum of five to six biopsies covering different segments of the large intestine is required. Ulcerative colitis is described classically as always involving the rectum and extending for a variable distance into the proximal colon, but in some cases this distribution is not seen. Waxing and waning of the disease and the effect of partial treatment may result in sparing of the rectum and/or disease that shows a patchy distribution on endoscopic and/or histopathological examination. Furthermore, it is possible that the degree of inflammation assessed endoscopically may not completely correlate with the presence of inflammation within corresponding mucosal biopsies. In a patient in whom there is an otherwise confident diagnosis of ulcerative colitis, the presence of these features alone should not result in a change of diagnosis from ulcerative colitis to Crohn's disease. It is also entirely possible for mucosal biopsies from patients with quiescent IBD to have a histopathological appearance that is indistinguishable from normal. Therefore, the presence of microscopically normal colorectal mucosa does not preclude a diagnosis of previously active IBD.