AIM: To investigate the effect of prophylaxis withantibiotics on clinical adverse events in patients who underwent endoscopic submucosal dissection(ESD) or endoscopic mucosal resection(EMR) for colorectal lesions.METHODS: From June 2011 to December 2013, a total of 428 patients were enrolled into the study, of which 214 patients admitted to hospital underwent EMR or ESD procedures. These patients were randomized to an antibiotic group, in which patients were given cefuroxime 1.5 g iv half an hour before and 6 h after surgery respectively, and a control group, in which patients were not given any antibiotic. A further 214 outpatients with small polyps treated by polypectomy were compared with controls that were matched by age and gender, and operations were performed as outpatient surgery. Recorded patient parameters were demographics, characteristics of lesions and treatment modality, and the size of the wound area. The primary outcome measures were clinical adverse events, including abdominal pain, diarrhea, hemotachezia, and fever. Secondary outcome measures were white blood cell count, C-reactive protein and blood culture. Additionlly, the relationship between the size of the wound area and clinical adverse events was analyzed. RESULTS: A total of 409 patients were enrolled in this study, with 107 patients in the control group, 107 patients in the antibiotic group, and another 195 cases in the follow-up outpatient group. The patients’ demographic characteristics, including age, gender, characteristics of lesions, treatment modality, and the size of the wound area were similar between the 2 groups. The rates of adverse events in the antibiotic group were significantly lower than in the control group: abdominal pain(2.8% vs 14.9%, P < 0.01), diarrhea(2.0% vs 9.3%, P < 0.05), and fever(0.9% vs 8.4%, P < 0.05) respectively. The levels of inflammatory markers also decreased significantly in the antibiotic group compared with the control group: leukocytosis(2.0% vs 11.2%, P < 0.01), and C-reactiveprotein(2.0% vs 10.7%, P < 0.05). Additionally, clinica adverse events were related to the size of the surgica wound area. When the surgical wound area was larger than 10 mm × 10 mm, there were more clinica adverse events.CONCLUSION: Clinical adverse events are not uncommon after EMR or ESD procedures. Prophylactic antibiotics can reduce the incidence of clinical adverse events. This should be further explored. AIM: To investigate the effect of prophylaxis withantibiotics on clinical adverse events in patients who underwent endoscopic submucosal dissection(ESD) or endoscopic mucosal resection(EMR) for colorectal lesions.METHODS: From June 2011 to December 2013, a total of 428 patients were enrolled Into the study, of which 214 patients admitted to hospital underwent EMR or ESD procedures. These patients were randomized to an antibiotic group, in which patients were given cefuroxime 1.5 g iv half an hour before and 6 h after surgical respectively, and a control group , in which patients were not given any antibiotic. A further 214 outpatients with small polyps treated by polypectomy were compared with controls that were matched by age and gender, and operations were performed as outpatient surgery. Recorded patient parameters were were demographics, characteristics of lesions and Treatment modality, and the size of the wound area. The primary outcome measures were clinical adverse events, including a RESULTS: A total of: The secondary outcome measures were white blood cell count, C-reactive protein and blood culture. Additionlly, the relationship between the size of the wound area and clinical adverse events was analyzed. 409 patients were enrolled in this study, with 107 patients in the control group, 107 patients in the antibiotic group, and another 195 cases in the follow-up outpatient group. The patients’ demographic characteristics, including age, gender, characteristics of lesions, The treatment modality, and the size of the wound area were similar between the 2 groups. The rates of adverse events in the antibiotic group were significantly lower than the control group: abdominal pain (2.8% vs 14.9%, P < 0.01), diarrhea (2.0% vs 9.3%, P < 0.05), and fever (0.9% vs 8.4%, P < 0.05) respectively. The levels of inflammatory markers also decreased significantly in the antibiotic group compared with the control group: leukocytosis (2.0% vs 11.2%, P < 0.01), and C-reactive protein (2.0% vs 10.7%, P < 0.05). Additionally, clinica adverse events were related to the size of the surgica wound area. When the surgical wound area was larger than 10 mm × 10 mm, there were more clinica adverse events.CONCLUSION: Clinical adverse events are not uncommon after EMR or ESD procedures. Prophylactic antibiotics can reduce the incidence of clinical adverse events. This should be further explored.