Pus Samples in Complicated Appendicitis: An Important Investigation or a Waste of Resources: A Prospective Cohort Study

Background and Aims: Appendicitis is a common presentation to hospital with appendectomy being the treatment of choice. Pre-operative administration of broad-spectrum antibiotics is common, but obtaining intra-abdominal pus samples is not. After an initial 6-month retrospective audit and departmental teaching on the importance of intra-peritoneal pus sampling, we aimed to determine whether intra-operative pus samples changed antibiotic management. Materials and Methods: Following the initial audit cycle, a 6-month prospective cohort study was conducted. Clinical data were collected on a predetermined proforma to assess the effectiveness of the intervention and antibiotic prescribing practice. The data collected during the whole 1-year period was analyzed. Results: During the 1-year period, 440 patients were identified as undergoing a laparoscopic procedure. After exclusion, 261 patients were identified as undergoing laparoscopic appendectomies, of which 141 (54%) were classified as complicated laparoscopic appendectomies. A total of 35 out of 141 (25%) pus samples were sent of which 24 (17%) resulted in positive cultures, with only nine of these positive cultures reported prior to the patient being discharged. No patient had their antibiotic regimen changed as a result of the culture results. There were three cases of cultures resistant to local antibiotics, but without significant clinical outcome. One of these patients developed a post-operative complication, but the antibiotic regimen was changed to broad spectrum rather than a specific antibiotic based on culture sensitivity. Of the 141 patients with complicated laparoscopic appendectomies, five (3.5%) developed post-operative complications: one readmission requiring a laparoscopic washout for pelvic collection, three (2%) cases of pelvic collections managed conservatively, and one case of prolonged paralytic ileus managed non-operatively. Conclusion: Overall, none of the patients with positive cultures had a change in prescribed antibiotics based on culture results. Hence, the routine practice of intra-peritoneal pus sampling following complicated appendicitis remains of little clinical value.