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Abstract
Aims In this study, we aim to determine whether combining multiple small colorectal polyps within a single specimen pot can reduce carbon footprint, without an associated deleterious clinical impact.
Methods This was a retrospective observational study of colorectal polyps resected during 2019, within the Imperial College Healthcare Trust. The numbers of pots for polypectomy specimens were calculated and corresponding histology results were extracted. We modelled the potential reduction in carbon footprint if all less than 10 mm polyps were sent together and the number of advanced lesions we would not be able to locate if we adopted this strategy. Carbon footprint was estimated based on previous study using a life-cycle assessment, at 0.28 kgCO2e per pot.
Results A total of 11 781 lower gastrointestinal endoscopies were performed. There were 5125 polyps removed and 4192 pots used, equating to a carbon footprint of 1174 kgCO2e. There were 4563 (89%) polyps measuring 0–10 mm. 6 (0.1%) of these polyps were cancers, while 12 (0.2%) demonstrated high-grade dysplasia. If we combined all small polyps in a single pot, total pot usage could be reduced by one-third (n=2779).
Conclusion A change in practice by placing small polyps collectively in one pot would have resulted in reduction in carbon footprint equivalent to 396 kgCO2e (emissions from 982 miles driven by an average passenger car). The reduction in carbon footprint from judicious use of specimen pots would be amplified with a change in practice on a national level.
- COLONOSCOPY
- POLYP
- ENDOSCOPIC POLYPECTOMY
Data availability statement
Data are available on reasonable request.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Healthcare sector is known to incur a sizeable carbon footprint.
Endoscopy department is the third-highest contributor to waste per bed per day.
Small polyps have very low rates of advanced histology between 0.1% and 12%.
WHAT THIS STUDY ADDS
Combining small polyps in a single specimen pot can have significant reduction in carbon footprint.
Within our study population, only 0.1% were polyp cancers and 0.2% have high-grade dysplasia.
No deleterious clinical impact of combining small polyps in a single specimen pot.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
The reduction in carbon footprint from judicious use of specimen pots can be amplified with a wider adoption of this practice on a national and international level.
Introduction
The contribution of the healthcare sector to the global carbon footprint is being increasingly recognised. The National Health Service (NHS) in the UK is the largest publicly funded health system worldwide and is estimated to generate nearly 590 000 tonnes of waste annually.1 The endoscopy department is thought to be the third highest contributor of waste per bed per day, including a significant amount of single use plastic specimen pots. Therefore, innovations in minimising use of plastic specimen pots in endoscopy departments will have a crucial role in reaching net-zero emissions by 2045.2 3
While major change will require changes in supply chains, technology, decontamination processes and reducing the number of procedures performed, such interventions require a substantial time and capital investment.4 The current trajectory of climate change demands an immediate stepwise series of small but positive changes. A life-cycle assessment used to quantify carbon footprint in endoscopy has identified that 36% of emissions are related to the histological processing of tissue samples.5 We aim to evaluate the convention of sending colorectal polyps resected during endoscopy as separate samples. While this practice may aide reassessment of specific parts of the colon if the polypectomy specimen has advanced histology, we know that polyps ≤10 mm have a negligible risk of malignancy and such precaution may be unwarranted.6 7
The aim of this study is to describe the size of the impact on carbon footprint from sending colorectal polyps as combined samples and to determine whether this strategy has any negative clinical impact.
Methods
Study design and data source
This was a retrospective observational study evaluating all polyps identified and resected at colonoscopy or flexible sigmoidoscopy between 1 January 2019 and 31 December 2019, within the three hospital sites of the Imperial College Healthcare NHS trust, London (St Mary’s, Charing Cross and Hammersmith Hospitals). Assumptions regarding the processing of histopathology samples were reviewed by a histopathologist.
All procedures with at least one polyp diagnosed were identified through our electronic endoscopy reporting system, SCORPIO (MEDILOGIK, Ipswich, UK). We undertook a per procedure analysis, where if an individual patient underwent more than one procedure, these were considered as separate interventions. Incomplete colonoscopies where polyps were identified and resected were included. Procedures where polyps were identified but not removed or where polyps were resected but not retrieved were excluded. Endoscopy reports were analysed to determine patient characteristics such as patient date of birth, gender and procedure indication. Polyp characteristics, including size, morphology, location and histology, were recorded. We examined the endoscopy report to establish whether the endoscopist predicted any of the resected polyps have an advanced histology based on endoscopic features and if they were marked with tattoo.
Analysis of biopsy pot usage
We evaluated the histology report to establish the number of pots received by the laboratory. Additional pots sent for biopsy samples, other than excised polyps, were not included.
We determined that a number of pot usage if all polyps less than 10 mm were placed within a single colonic segment (rectum, sigmoid, descending, splenic flexure, transverse, ascending and caecum), hemicolon (right hemicolon: caecum to ascending colon; left hemicolon: hepatic flexure to sigmoid and rectal) or throughout the colon. The hemicolon classification reflects conventional surgical resection strategies when a malignant polyp is diagnosed.
Carbon footprint estimation
Estimates of the carbon footprint were based on previous work in this area, which described the processing of a single pot with an emission of 0.28 kgCO2e.5 Our local pathway from tissue processing to production of histology report was in accordance with the Royal College of Pathology Tissue Pathway.8
Statistical analysis
Statistical analysis was performed by using IBM SPSS Statistics for Windows, V.28.0 (IBM). A p<0.05 was considered statistically significant. Descriptive statistics were used to report the data. The statistical significance in reduction in carbon footprint by putting all small polyps in whole colon was analysed with Z test. Features predictive of the diagnosis of a polyp cancer were investigated using logistic regression.
Results
During the 12-month study period, a total of 11 781 lower gastrointestinal (GI) endoscopies were performed across the three hospital sites included within this study. There were 219 (1.9%) procedures that detected polyps but not removed, while in 146 (1.2%) procedures polyps were removed but not retrieved. These procedures were excluded, with the resultant study population encompassing 5125 polyps across 2502 procedures.
Our study cohort included 610 procedures (1281 polyps) performed as part of the Bowel Cancer Screening Programme (including the Bowel Scope Flexible Sigmoidoscopy Programme), 652 (1456 polyps) as a part of surveillance, while 1240 (2388 polyps) were for the investigation of GI symptoms. The mean age of the patients with a detected polyp was 63.9 years old (range 24–96), with a male preponderance (57.5% male).
The polyps removed consist of 3738 (73%) sessile, 378 (7.4%) pedunculated and 231 (4.5%) subpedunculated polyps. Polyps measured 0–10 mm consist of 93.4% sessile, 48.8% pedunculated and 68% of subpedunculated morphology. There were 0.3% of small sessile polyps and 1% of small pedunculated/subpedunculated polyps had advanced histology.
There were 2874 (56.1%) adenoma, 966 (18.8%) hyperplastic, 240 (4.7%) sessile serrated lesions, 115 (2.2%) inflammatory, 17 (0.3%) neoplastic and 913 (17.8%) had miscellaneous histological types. Polyps measuring 0–10 mm accounted for 4563 (89%) of all polyps resected (table 1).
Histological analysis of polyps according to polyp size
Within this study population, there were 64 (1.2%) polyps with advanced histology, 47 with high-grade dysplasia (HGD) and 17 with adenocarcinoma. When polyps measuring 0–10 mm were scrutinised, the rate of HGD and cancer was 0.2% and 0.1%, respectively. The rate of advanced histology in polyps ≤5 mm was 0.04%. Advanced histology in polyps 0–10 mm was predicted at the time of the procedure in 26 (40.6%) cases, using a combination of white light and narrow band imaging (NBI), with consequent tattoo application and documentation in the endoscopy report. The unexpected advanced histology resulted in 23 (63.9%) repeat colonoscopy or flexible sigmoidoscopy, 10 (27.8%) CT scans, 2 (5.6%) MRI pelvis, 1 (2.8%) Positron Emission Tomography (PET)scan and 11 (30.6%) had surgery. We were unable to determine the exact proportion of endoscopist who assesses the polyps with NBI. The use of NBI was not always explicitly mentioned in the formal endoscopy reports.
A single polyp was diagnosed in 1471 (58.8%) of the procedures performed. Where there were multiple polyps, 240 (9.6%) were confined to a single colonic segment, 441 (17.6%) confined to a hemicolon and 350 (14.0%) were distributed throughout the colon.
Within our department, we found that 4192 specimen pots were used for the 5125 polyps, across 2502 procedures. There were 1031 (41.2%) of procedures where there were multiple polyps. Individual pots were used per polyp in 756 (73.3%), while multiple polyps in the same colonic segment were combined in 160 (15.5%), per hemicolon in 111 (10.8%), and all in 1 pot in 4 (0.4%). There was no trend in the likelihood of any individual endoscopist using combined pots, with the decision seemingly arbitrary.
A total of 2718 pots were used for procedures with more than one polyp removed. If pots usage rationalised to sending all polyps measuring 0–10 mm with no suspicious endoscopic features in one pot per segment, one pot per hemicolon or one pot for the whole colon, this would reduce the number of pots used to 2043, 1749 and 1031, respectively. The reduction in pot usage would have resulted in a reduction in carbon footprint to 572 kgCO2e, 490 kgCO2e and 289 kgCO2e, respectively. The reduction in carbon footprint by putting all small polyps in a pot for the whole colon, in comparison with one pot per hemicolon was statistically significant (p<0.00001), as was the comparison between placing in segmental distribution versus hemicolon distribution.
When we analysed the number of polyps with unexpected advanced histology, there were a total of 38 polyps harbouring covert HGD or neoplasia. Within these polyps, 19 were complete (R0) resections at index polypectomy, with 5 of these patients requiring surgical resection. Out of the 64 polyps with advanced histology, the theoretical approach of combining small polyps into segmental, hemicolon or whole colon pots would make it challenging to locate the polyp to relevant hemicolon in 0, 1 and 4 cases, respectively.
When undertaking a binary logistical regression examining polyp features predicting the likelihood of advanced histology, we found that polyp size >10 mm, right-sided location and the screening population have a significant association (table 2). This would support combining ≤10 mm polyp samples.
Logistical regression examining the factors associated with the diagnosis of a polyp cancer
Discussion
Imperial College Healthcare Trust performed a total of 11 781 lower GI endoscopies in the year 2019. A total of 5125 polyps were removed across 2502 lower GI endoscopies and sent for histological evaluation in 4192 specimen pots. This practice was estimated to generate 1174 kgCO2e emission. This could be reduced to 2779 pots just by adopting the approach of combining small polyps within a single pot. The magnitude of this carbon footprint savings would equate to a reduction of 396 kgCO2e emission, and roughly to 982 miles driven by an average passenger car.9 Based on the national annual endoscopy volume of over a million lower GI procedures per year, if we were to extrapolate our data this effect could be multiplied 100-fold.10 This intervention is one that could be introduced immediately and without the requirement for capital expenditure. In fact, the use of fewer resources would result in cost savings.
Although the rate of advanced histology for polyps ≤10 mm were very low, the pedunculated/subpedunculated morphology appear to have a slightly higher rate of advanced histology compared with sessile polyps. However, the reason for this observation was unclear. Our data showed that these small pedunculated/subpedunculated polyps tend to be solitary within the same colonic segment. Therefore, it may still be safe to put them collectively in the same specimen pot with other small sessile polyps, as long as it was clearly stated in the endoscopy report to facilitate re-examination of the site if confirmed to be an advanced histology.
The convention of placing polyps in separate pots stem from the concept of being able to relocate the area of resection in the event that the polyp harbours advanced histology. However, it may still be difficult to pinpoint the exact location within a colonic segment, given that resection of small polyps rarely results in a scar. The technological advancement of colonoscopes and wide availability of chromoendoscopy should aide endoscopist in identifying high-risk features of polyps. It would be expected that most advanced lesions are recognised at the time of the procedure and a tattoo placed to mark the location.11 Note is made of the moderate rate endoscopic prediction of advanced lesions in our cohort of 40.6%.
A further possible extension of this concept would be the adoption of the ‘Resect and Discard’ approach, whereby instead of sending diminutive (≤5 mm) colorectal polyps for analysis, the in vivo optical analysis is relied on, and the sample is discarded. This would reduce carbon footprint further by virtue of not sending the polyp for analysis. In our cohort, this would result in discarding 3429 (66.9%) of all polyps sent for analysis, equivalent to 960 kgCO2e saved if these were sent as individual samples. While there have been many studies supporting the resect and discard approach, there has been a failure for this to be taken up in daily practice, mainly due to a concern about suboptimal accuracy in polyp characterisation if this were to be extended across all hospital settings.12 Existing literatures suggest the accurate endoscopic prediction of advanced lesions for diminutive polyps ranges from 0.1% to 12%.13 In our cohort, there was advanced histology in two polyps ≤5 mm, which was not predicted by the performing endoscopist.
The UK Bowel Cancer Screening Programme stipulates that each polyp specimen should be submitted separately, and that accurate labelling of the specimen pot if more than one lesion collectively placed in the same specimen pot. However, it did not highlight the evidence base for this recommendation.14 According to our study, 34 (53.1%) of advanced polyps came from the Bowel Cancer Screening Programme and out of which, 10 (15.6%) polyps were ≤10 mm. Nevertheless, these small polyps with advanced histology only represented 0.8% of all polyps retrieved from Bowel Cancer Screening Programme. This study could provide initial evidence supporting the combination of small polyps into a single specimen pot for Bowel Cancer Screening Programme.
The rationalisation of the use of pots for colorectal polyps represents only a proportion of the impact that could be made within the endoscopy department. It is known that many unnecessary biopsies are taken at upper GI endoscopy such as biopsy of gastric polyps that have no malignant potential, gastritis and duodenal biopsies in anti-tissue transglutaminase negative individual.15 In addition, some aspects of national guidelines may be considered overzealous, with recommendation for histology acquisition for a range of presentations based on weak level evidence.16 17 Additional scenarios where biopsy pot numbers could be rationalised include sending a colonic series sent on a strip in a single pot, instead of separate pots in the context of inflammatory bowel disease.18 The efficacy and yet economical use of a single strip in handling of multiple biopsy specimens were highlighted in a previous study by Veitch and Fairclough19
Evaluating and optimising the pathway for samples going through the histopathology process may present a further opportunity to reduce the carbon footprint of the samples that do require analysis. Potential areas include using size appropriate pots for the tissue samples sent from the endoscopy department, recycling of single use components and encouraging reusable materials. Processing small polyps placed in a single pot, as a single block would result in an additional savings in energy consumption.
The main strength of this study was the large sample size, encompassing three hospital sites. We would expect the results to be replicable at other NHS trusts within the UK. We intentionally examined practice prior to the SARS-CoV-2 pandemic in order to obtain realistic values associated with normal endoscopy activity. The limitations of this study include its retrospective nature. As such, we are unable to definitively ascertain the reasons for using separate pots and whether this was intentional on the part of the endoscopist. Also, our cohort was an urban, relatively young, multiethnic population, which was associated with a lower prevalence of polyps and lower incidence of multiple polyps per procedure. As such, the results of this study are likely to be a conservative estimate of the population in general.
Conclusion
This study has highlighted a modest reduction in carbon footprint without deleterious patient impact in association with the rationalisation of the use of specimen pots. The reduction in carbon footprint from judicious use of specimen pots would be amplified with a change in practice on a national level, and even further if the concept were applied to other aspects of GI endoscopy. This innovation represents a small but significant step towards more sustainable endoscopy.
Data availability statement
Data are available on reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study was undertaken as part of service evaluation, with institutional approval obtained.
Footnotes
Contributors SB designed and supervised the study. Data were collected by KKY, YH, HCAC, RS and WJ. The manuscript was prepared by KKY, RG and SB. SB was the guarantor for the data of this study. The final manuscript was approved by all authors.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.