We sought to identify risk factors for colonoscopy-associated peritonitis in patients on CAPD. The overall peritonitis rate was 3.8%. Both polypectomy and EMR were peritonitis risk factors. Although statistical significance was not attained (p=0.067), peritonitis was absent in patients who received antibiotic prophylaxis prior to colonoscopy. To the best of our knowledge, this is the first multicentre study to explore the risk factors for colonoscopy-related peritonitis in patients on CAPD; we included the largest number of patients evaluated on this subject to date.
The principal causes of PD-related peritonitis are catheter infections, thus contamination of PD catheters and exit site and tunnel infections. Less often, microorganisms from the colon or vagina, or haematogenous dissemination after dental procedures, trigger peritonitis in patients on PD. [16, 17] We found that polypectomy and EMR were risk factors for peritonitis. The colonic mucosa prevents microorganism translocation and controls intestinal permeability. [18, 19] Polypectomy and EMR create colonic mucosal defects facilitating translocation of intestinal microorganisms. We found that colonic biopsy was not associated with a risk of peritonitis. Such mucosal defects may be smaller than those caused by polypectomy or EMR. Also, we removed colon polyps electrically, thus not via cold snaring. Compared with cold-snare polypectomy, hot-snare polypectomy and EMR damage the large bowel wall to greater extents. [20, 21] Thermal injury of the colonic mucosa may act synergistically with a mucosal defect to trigger peritonitis.
Of the 113 patients who did not undergo mucosal manipulation, peritonitis occurred in only 1 (0.8%). The causative organism was S. aureus. The causative organism depends on the infection site. Usually, Gram-positive bacteria cause catheter-related infections. However, Gram-negative bacteria are commonly translocated from the colon or vagina.  S. aureus is the most common causative agent of catheter-related peritonitis;  we could not exclude the possibility of catheter-related peritonitis in the abovementioned patient. Peritonitis resolved after catheter removal.
Were prophylactic antibiotics useful? Of the 236 patients, only 65 received such antibiotics. The overall peritonitis rate after colonoscopy was 3.8%. When we divided the patients into those who received prophylactic antibiotics and those who did not, the peritonitis rates were 0 (0/65) and 5.3% (9/171), respectively. Although statistical significance was not attained (p=0.067), peritonitis did not develop in any patient who received prophylactic antibiotics, in line with the findings of previous studies. [12, 14] Most studies found that the use of prophylactic antibiotics did not attain statistical significance in terms of peritonitis development. It is unethical to give patients placebos. We included patients on CAPD who underwent colonoscopy from 2003 to 2012, of whom a relatively small proportion (27.5%) received antibiotics prior to colonoscopy. We gave antibiotics prior to colonoscopy from 2010. Colonic neoplasms are found in up to 50% of patients undergoing colonoscopy. [22-25] Although diagnostic colonoscopy lacking a therapeutic procedure may not cause peritonitis, physicians cannot predict the presence of colon polyps. Therefore, prophylactic antibiotics should be given to all patients on CAPD prior to colonoscopy.
Our study had several strengths. First, this is the first multicentre study to explore whether colonoscopy triggers peritonitis in patients on PD. Second, we investigated factors causing peritonitis and identified advanced procedures such as polypectomy and EMR as triggers.
Several limitations of the study should be addressed. The work was retrospective in nature. Some data were lacking. Colonoscopy procedure time, which might affect peritonitis development, was not recorded. We did not include patients on automated PD (APD), but rather only CAPD patients. Peritoneal fluid triggers peritonitis. As patients on APD do not retain peritoneal fluid during the day, we hypothesized that patients on CAPD are at a higher risk of colonoscopy-related peritonitis than are patients on APD; thus, our findings may not be applicable to patients on APD. In addition, we just surveyed the use of prophylactic antibiotics, not antibiotic regimens. Further studies of prophylactic antibiotic regimens are needed to prevent colonoscopy-related peritonitis in CAPD patients.