the number of complications associated with therapeutic colonoscopy has increased with the increasing number of these procedures . of these complications , the incidence of perforation is even higher during endoscopic submucosal dissection ( esd ) in the colorectum [ 1 - 3 ] . the risk factors for colorectal esd - associated perforation include inexperience on the part of the endoscopist ( i.e. , has performed < 50 esd procedures ) , a large tumor size , and submucosal fibrosis . colonic perforation during colonoscopic polypectomy or colorectal esd occurs as a result of unintended endoscopic resection / dissection and/or thermal injury . in the former case , immediate perforation predominantly occurs ; that is , colonic wall defects are seen during the procedure . however , in the case of thermal injury , the postprocedural ulcer base may demonstrate whitish coagulation damage , and delayed perforation mainly occurs . we here report a case in which delayed perforation occurred after performing esd on a laterally spreading tumor ( lst ) in the colon . this perforation was completely unexpected because there were no esd - associated risk factors for this complication in the patient , and no severe coagulation damage was apparent at the post - esd ulcer base . a 43-year - old man was referred to our center for the endoscopic resection of a nongranular lst ( lst - ng ) in the transverse colon . the colon was well prepared , and a flat , elevated lst - ng measuring 2022 mm was observed in the transverse colon . the lesion was type iv with a kudo pit pattern , and clinically suggestive of noninvasive neoplasia . a submucosal cushion was created with a saline injection , and no nonlifting sign or submucosal fibrosis was noted . submucosal dissection was performed with a fixed flexsnare knife ( kachu medico co. , seoul , korea ) . after the dissection of the lesion ( except for the central portion ) , the residual attached portion was snared and removed en bloc . the duration of electrocauterization ( i.e. , the duration of submucosal dissection and snaring ) was 23 minutes , and the total procedure time was 43 minutes . no barotraumas , deep thermal injuries , or other complications such as immediate bleeding or perforation were noted during the procedure . the post - esd ulcer base was clean without bleeding , deep coagulation injury , or perforation ( fig . 1 ) . the patient had no abdominal pain and his vital signs were stable after colonoscopic resection . sips of water were allowed , and he complained of severe abdominal pain several hours later . the same symptoms returned when sips of water were allowed a few hours later . direct tenderness of the whole abdomen was noted on physical examination . his vital signs were stable ; however , free air under the right diaphragm was noted on simple abdominal images ( fig . his white blood cell count was 2800/l , and the c - reactive protein concentration was 5.85 mg / dl . abdominopelvic computed tomography was performed 30 hours after the procedure , which revealed a pneumoperitoneum and wall irregularities at the endoscopic resection site ( fig . 2 ) . empirical antibiotics were administered , and an emergency laparoscopic operation was performed because the symptoms rapidly aggravated and the whole abdomen demonstrated rigidity with rebound tenderness , suggesting severe , aggravating peritonitis . primary repair was performed after massive irrigation of the soiled feces and removal of necrotic colon tissue . the final pathologic diagnosis of the endoscopic resection specimen was mixed traditional serrated adenoma and tubular adenoma with clear resection margins . 3 ) . the surgically resected colon specimen demonstrated wall necrosis , neutrophil infiltration , and a large hematoma in the adjacent proper muscle layer ( fig . therapeutic colonoscopy demonstrates a higher perforation rate than does diagnostic colonoscopy ( 0.15% to 3% ) , and the mortality rate can be as high as 13% [ 1 - 3,5 ] . our current case demonstrated delayed perforation , which is not uncommon , accounting for 6% to 40% of colon perforations , mainly after therapeutic colonoscopies [ 5 - 7 ] . most notably , esd , which was originally developed for the en bloc resection of large or ulcerative gastric epithelial neoplasms , demonstrates a high perforation rate ranging between 1.7% and 20.4% [ 4,8 - 11 ] . in our current case , esd with snaring is a simplified alternative to esd alone for the en bloc resection of large colorectal lesions . although the procedure duration of esd with snaring is usually shorter than that of esd without snaring , the perforation risk associated with esd with snaring was not significantly lower than that of esd without snaring ( 3% vs. 7% , p=0.24 ) in our previous study . perforation can occur after colonoscopy and it is not a negligible complication , and therefore determining if the patient or the procedure has any risk factors for colon perforation would help promote safe clinical practice . the risk factors for colonoscopic perforation include female sex , comorbidities , older age ( > 75 years ) , diverticulosis , bowel obstruction , and a history of intra - abdominal surgery . in the case of colorectal esd , a large tumor size ( i.e. , 50 mm ) , an inexperienced endoscopist , and submucosal fibrosis are well - known risk factors for perforation . however , none of these factors were present in our current case . in addition , during the procedure , there was neither a deep dissection that injured the proper muscle layer nor excessive thermal injury that resulted in severe coagulation damage to the submucosa and proper muscle . furthermore , the endoscopic resection specimen did not reach the proper muscle layer or indicate severe tissue injury . we suggest several possible explanations for the unexpected perforation in our case , on the basis of the histopathology of the surgical specimen . first , when considering a large hematoma in the proper muscle layer adjacent to the perforation site , a high - tension colonic wall might lead to perforation . however , perforation did not occur at the center of hematoma where the wall tension might be highest . a second possibility is that acute infection followed by massive inflammation and necrosis in the colonic wall may have occurred because there was severe neutrophil infiltration . therefore , it is difficult to know the causal relation between neutrophil infiltration and necrosis . third , delayed perforation may occur because of the excessive electrical coagulation of vessels in the submucosa and proper muscle layer . a long duration of electrocauterization may predispose vessels to coagulation injury , thereby resulting in delayed perforation . in our case , this cautery duration is longer than the average cautery time of conventional polypectomy , which is usually < 1 minute . thus , the perforation mechanism in our current case remains unclear , and we believe several mechanisms together may have contributed to this adverse event . the treatments for perforation include surgical and nonsurgical management . in the past , surgery was the mainstay of treatment and medical management was only performed on select patients . however , as endoscopic clipping techniques have progressed , the need for and the frequency of surgery have decreased . our group has reported the clinical courses of 38 perforations after both diagnostic ( n=13 ) and therapeutic ( n=25 ) colonoscopies . of these cases , only nine patients ( 23% ) required surgery . however , patients who receive a nonsurgical intervention should receive close follow - up examinations because immediate surgery needs to be performed if clinical deterioration occurs . surgery is indicated for patients with large perforations , generalized peritonitis , ongoing sepsis , and deterioration despite being managed conservatively . in our current case , rapid progressive abdominal pain with tenderness and rebound tenderness developed in the whole abdomen , indicating severe , generalized peritonitis . severe peritoneal soiling with large necrotic tissue at the endoscopic resection site was noted in the surgical field . we believe that endoscopic clipping may have resulted in the adverse outcome in our case because we could not clean the soiled content , and successful clipping may have been prevented by the necrotic wall . thus , we believe the decision to perform emergency surgery was appropriate . therapeutic colonoscopy , which has dramatically evolved in recent years , is an important modality for the treatment of colonic neoplasm . however , as shown in our current case , unexpected critical complications such as perforation can develop . endoscopists should always keep in mind that perforation can develop even after clean procedures , and should closely evaluate any complaints about unexplained abdominal pain after therapeutic colonoscopy procedures , including polypectomy and esd .
colonic perforation may occur as a complication of diagnostic and therapeutic colonoscopy . 
 the risk factors for perforation after colorectal endoscopic submucosal dissection ( esd ) include an inexperienced endoscopist , a large tumor size , and submucosal fibrosis . 
 the mechanisms of perforation include unintended endoscopic resection / dissection and severe thermal injury . here , we report a case of colon perforation that occurred after esd with snaring of a laterally spreading tumor . 
 the perforation was completely unexpected because there were no colorectal esd - associated risk factors for perforation , deep dissection , or severe coagulation injury in our patient .