LAUSR

Clostridioides difficile infection (CDI) following ileostomy reversal is a potentially fatal, but underappreciated post-operative complication. In addition to prolonging hospital stay by 4 to 11 days, CDI is associated with a three times higher rate of reoperation, six times higher incidence of post-operative mortality, and significantly increased health care costs. Its reported incidence is variable, but ranges from 1.8% to 5.6%. Importantly, it is more common after ileostomy reversal versus elective bowel resection. For instance, the largest study of 2235 patients by Skancke et al. observed a 3.04% incidence of CDI after ileostomy reversal versus 1.25% for elective colonic resection. Similarly, Randall et al. reported that the CDI rate was higher following ileostomy reversal (4.2%) compared with right hemicolectomy (2.1%) and anterior resection (1%). Proposed mechanisms for this discrepancy in incidence of CDI following reversal of ileostomy compared with colonic resection include changes in the colonic microbiome due to diversion of faecal stream as well as ileal CD colonization. Prior to ileostomy reversal, asymptomatic ileal CDI may go unnoticed while symptomatic ileal CDI might be misdiagnosed as ‘high output ileostomy’. In a healthy gut, specific host defence mechanisms provided by the microbiome may prevent CDI. Thus, a disused colon may be more prone to CD colonization, because of a disturbed composition of commensal colonic bacteria. In patients with a temporary ileostomy, potential contributors to small and large intestine microbial dysbiosis include adjuvant chemotherapy, antibiotic usage, overuse of proton pump inhibitors as an anti-secretory agent for high output ileostomy, and prolonged time to closure. The true incidence of CDI following reversal of loop ileostomy is probably significantly higher than in the literature. This is because mild-to-moderate diarrhoea after ileostomy reversal is common. For example, a recent retrospective study of 178 ileostomy reversal patients found that 29 (16.3%) developed mild non-CD diarrhoea. These symptoms are often ascribed to normal colonic readaptation after disuse or altered bowel function as part of low anterior resection syndrome. Thus, many patients with diarrhoea following ileostomy reversal are not tested for CD, especially if symptoms develop after discharge from hospital. How can we reduce the incidence of CD colitis in patients following ileostomy reversal? First, we should aim to reverse ileostomies in a timely fashion. An interval to ileostomy reversal greater than 1 year significantly increases the risk of CDI. While these delays are sometimes due to on-going adjuvant therapy, they are often due to waiting lists prioritizing more surgeries that are urgent. The median time to reversal in an Australian public institution was already 12 months before the onset of the COVID19 pandemic, a situation which is no doubt similar to other Australasian institutions. These delays have certainly been further exacerbated in the post-pandemic period, where a resumption of non-urgent elective procedures has put considerable strain on surgical services. Highlighting one possible solution, the CLOSE-IT study from the UK reported a median time to ileostomy closure of 259 days. The authors estimated that listing patients prior to their surgical follow up clinic and imaging could reduce the interval to closure by 168 days. Second, we should optimize patients prior to surgery, focusing on improving any modifiable risk factors. It is becoming clear that the immune system plays an important role in regulating the gut microbiome. Skancke et al. have identified that smoking, use of steroids and presence of disseminated cancer all increase the risk of CDI after ileostomy reversal. Therefore, enrolment in a smoking cessation programme and judicious use of steroids tapering protocols may potentially reduce the risk of CDI following ileostomy reversals. Third, the choice of intravenous antibiotics at the time of surgery also appears to play an important role. Fernandes et al. report that a single dose of metronidazole at induction significantly reduces postoperative diarrhoea and CDI following ileostomy reversals compared with multiple-dose cefuroxime plus metronidazole. Trends to offer patients combination antibiotics prior to colorectal surgery to reduce surgical site infection may paradoxically increase the risk of CDI following ileostomy reversals. Fourth, screening of patients prior to their ileostomy reversal could potentially have a significant effect on reducing the incidence of CDI. Hussain et al. report that CD colonization in the excluded colon is calculated to be between 6% and 44%, which is higher than the incidence in the healthy adult population (3%). Screening could be performed using a rectal swab taken as part of the preoperative assessment clinic or through collecting faecal samples obtained during their preoperative flexible sigmoidoscopy check on their anastomosis. Ileal content could also be tested for CD colonization or infection. For patients who are detected to be carriers of CD, they could be treated with rectal metronidazole suppositories or be enrolled in a distal limb chyme re-infusion or probiotic programme that has been shown to reduce diversion colitis, and may help restore the microbiome of the diverted colon. Lastly, we should consider if a defunctioning ileostomy is required in the index operation. Fluorescence imaging can be used to assess conduit perfusion and increase surgeon confidence that an