The risk of perforation from colonoscopy is 2-4 times greater than that from flexible sigmoidoscopy. Possible explanations for an increased rate of CP in patients with advanced age include the fact that the elderly have a declining colonic wall mechanical strength as recognized in colonic diverticular diseases, and they often have a greater frequency of abnormal colorectal findings which may require endoscopic intervention. Patients over 75 years of age also have an approximately 4-6 fold rise in the CP rate as opposed to younger patients. Several investigators have reported that some endoscopic interventions are associated with an increased CP rate, including polypectomy for polyps larger than 20 mm, pneumatic dilatation for Crohn’s stricture, the use of argon plasma coagulation, endoscopic mucosal resection and endoscopic submucosal dissection for colorectal neoplasia. The increased likelihood of CP in therapeutic endoscopy is because the perforation during therapeutic colonoscopy can occur not only through mechanisms that are similar to those seen for diagnostic colonoscopy (mechanical injury or barotrauma), but also through the fact that endoscopic interventions per se can cause perforation. There has been convincing evidence that therapeutic colonoscopies have a significantly higher rate of CP than diagnostic colonoscopies. Pelvic adhesions following previous pelvic operation or infection also contribute to a high incidence of sigmoid perforation. Additionally, the sigmoid colon is commonly involved with diverticular formation, and the muscular layer of the bowel wall may be thin or fragile due to previous inflammation (diverticulitis). A forceful insertion of an endoscope while having a sigmoid loop formation is the leading cause of anti-mesenteric bowel perforation due to an overextension of bowel by the shaft of the endoscope. Several factors making this bowel segment vulnerable to being injured include a sharp angulation at either the rectosigmoid junction or the sigmoid-descending colon junction, and the great mobility of the sigmoid colon. The most common site of colonic perforation is the rectosigmoid colon. The incidences of CP in some larger series (sample size > 30 000 cases) published from 2000 onwards are shown in Table Table1 1. Interestingly, rectal perforation during colonoscopic retroflexion was reported to be around 0.01%. Meanwhile, the incidence of CP following flexible sigmoidoscopy varies from 0.027% to 0.088%.
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