The healthcare sector contributes significantly to carbon emissions, which leads to devastating impacts on the environment¹ and on human health. It is our responsibility to promote sustainable work practices, and reduce carbon emissions where possible, without negatively impacting on the quality of patient care. Chronic diarrhoea is a common indication for lower GI endoscopy. In a macroscopically normal appearing colon, current practice is to take biopsies to assess for microscopic colitis (MIC), looking for histological changes of lymphocyte infiltration or a collagenous subepithelial band. This is a relatively uncommon condition, but with increasing prevalence². ESGE guidelines suggest biopsies should be taken from the right and left side of the colon and sent to pathology in separate containers³. While based on expert histopathological opinion, this recommendation was not supported by robust evidence. We have previously demonstrated 100% sensitivity for MIC with a right sided biopsy protocol in a multicentre retrospective review⁴. Our local histopathologists confirmed there is no diagnostic benefit in separating left and right specimens for this indication. We reviewed our biopsy practice and assessed potential reductions in carbon emissions that could result from a change in practice.

Patients referred for colonoscopy to investigate chronic diarrhoea (January–March 2024) were identified. Cases with a macroscopically normal colon were isolated. Biopsy practice for the assessment of microscopic colitis was analysed, including the number of biopsies taken, location biopsied and the total number of histopathology containers sent to the laboratory. Findings were compared with current ESGE guidelines. A previous time motion assessment had been completed in our lab to calculate the total staff time per container⁴. Data on CO2 emissions generated by processing each histopathological sample was estimated based on previous studies. From this, we assessed the potential reduction in carbon emissions with adherence to the current ESGE guidelines and then compared to our proposal; that all biopsies could be inserted into the one container. 

A total of 205 colonoscopies were performed for chronic diarrhoea during the study period. Patients with a history of IBD, or poor prep requiring repeat procedure (43%, n= 89) were excluded. A total of 351 containers were sent to pathology, a mean number of was 3.02 per case,  and a range of 0-7. The recommended right and left biopsies were sent in 20 (18.8%) of cases, with a single pot of random colon biopsies sent in 5 cases (4.7%). Biopsies were taken from a macroscopically normal terminal ileum in 51 cases (48.1%). No cases of microscopic colitis were confirmed. Time-motion assessment found the mean total staff time per biopsy container was 8 min 37s, resulting in time savings of 2.6 working days for laboratory staff per year, if we reduced to a single container. The carbon emissions resulting from analysis of colon biopsies is 0.29 kg CO₂ equivalent (CO₂e) per container⁵,  producing CO₂e of 407.26kg/year with current practice. Adherence to ESGE Guidelines would produce savings of 138.04 CO₂e or 272.6kg CO₂e if a single container protocol was adopted - annual savings of 1090.4KgCo₂e or the equivalent of 4467km driven by a petrol-powered vehicle⁶.

Auditing adherence to biopsy guidelines can result in significant reductions in inappropriate sampling and container use, leading to significant improvements in Co2e and workload. The use of a single container protocol can further reduce carbon emissions while investigating for MIC.  We found no cases of MIC in our study, but discovered that endoscopists took many more than the recommended number of biopsies. This included at the terminal ileum, taken in nearly half of cases, without any additional diagnostic benefit. We propose that right and left colon biopsies should be collected in a single container, to further decrease carbon emissions and the burden on histopathology.