Colon capsule endoscopy: Can it contribute to green endoscopy?

Abstract

Climate change due to sustained carbon dioxide (CO₂) emissions poses a serious threat to human existence, such as extreme weather events that must be addressed in all sectors of society. Gastrointestinal endoscopy is a healthcare sector that produces high levels of CO₂ emissions. Colonoscopy (CS) is the gold standard for colorectal cancer (CRC) screening that reduces the number of CRC-related deaths. However, vast amounts of cleaning solutions used to disinfect the colonoscope are disposed of, and multiple nonrenewable wastes are generated in performing CS, which significantly impact the environment. Currently, colon capsule endoscopy (CCE) retains good accuracy and has excellent potential to reduce CO₂ emission through a simple procedure. However, to date, colon capsules are single-use and lack a clear collection pathway. In addition, there is a lack of specific data regarding the environmental impact of CCE. Further research is needed to prove that CCE is a more environmentally friendly tool than CS.

Key Words: Carbon dioxide emission; Colon capsule endoscopy; Colonoscopy; Colorectal cancer screening; Green endoscopy

Core Tip: Climate change caused by carbon dioxide (CO₂) emissions is an urgent and inevitable global emergency. The gastrointestinal endoscopy unit has a higher CO₂ footprint than other units in healthcare facilities. Colonoscopy (CS) contributes significantly to CO₂ emissions. Colon capsule endoscopy (CCE) can potentially reduce the number of CS cases and CO₂ emissions from medical procedures. However, to date, colon capsules are single-use, with no clear collection pathway available. In addition, there are no concrete data or studies to support these claims. Further research is, therefore, required to prove CCE as a more environmentally friendly alternative to CS.

INTRODUCTION

Climate change caused by persistent carbon dioxide (CO₂) emissions has increased global surface temperatures. Consequently, extreme weather events, such as heat waves and floods, are becoming more frequent and severe. These may cause a reduction of up to 3060000 disability-adjusted life years in human health annually[1]. In 2021, the earth’s surface temperature was 1.04 °C higher than in pre-industrial times[2]. A 1 °C increase in global temperature could displace 1 billion people or force them to live in a heat wave[2]. According to the 2022 Emissions Gap Report, China, the United States, and India were the top-three countries in terms of total greenhouse gas (GHG) emissions[2]. Analysis of the percentage of international healthcare CO₂ emissions in the Organization for Economic Co-operation and Development countries has shown that the Netherlands (8.1%) had the largest footprint, followed by the United States (7.9%), Belgium (7.7%), and Japan (7.6%)[2]. The carbon footprint is the total amount of GHG emitted directly or indirectly by human action and is expressed as the CO₂ equivalent (CO₂e). Healthcare produces 2.0 gigatonnes (2 × 10⁹ tons) of CO₂e per year[1]. It accounts for approximately 4.4% of global CO₂ emissions[1].

CO₂ emissions from medical institutions can be broadly classified into three categories: Scope 1-Direct emissions: These originate from sources directly controlled by medical institutions. Examples include fuel combustion for on-site heating, cooling, and electricity generation (e.g., boilers and generators), anesthetic gases used during surgeries, on-site incineration of medical waste, and fugitive emissions from refrigerants used in medical equipment. Scope 2-Indirect emissions from purchased energy. These emissions are not directly produced by medical institutions but are associated with the electricity, heat, or steam they acquire from external providers. Scope 3-All other indirect emissions. These indirect emissions occur across the entire lifecycle of the medical institution's activities but are not directly controlled by them. Examples include emissions associated with the manufacturing and disposal of medical equipment and pharmaceuticals, and emissions from patient and staff travel (commuting by car and ambulance)[3]. It is estimated at 15%–50% in scope 1 and 2 and 50%-75% in Scope 3 for total emissions[4].

Among medical institutions, the endoscopy department contributes significantly to the environmental footprint of healthcare. Each endoscopic examination generates 28 kg of CO₂e[3], or approximately 3.09 kg of CO₂e daily waste per bed[5]. These departments are also responsible for 13500 tons of plastic waste annually in the United States[5]. In healthcare, gastrointestinal endoscopy (GIE) is the third-highest CO₂ emission-generating procedure[6]. The reasons for this include the high number of cases, generation of nonrenewable waste, use of disposable equipment, frequent cleaning and reprocessing of endoscopes, and frequent travel of patients and healthcare workers to hospitals.

Practical actions to reduce the environmental impact of GIE include: (1) Adhering to guidelines; (2) Implementing audit strategies to determine the appropriateness of GIE for patients; (3) Avoiding unnecessary endoscopic procedures; (4) Using medication rationally; (5) Digitalization; (6) Telemedicine; (7) Critical pathways; (8) Outpatient centered procedures; (9) adequate waste management; and (10) avoiding single-use devices[2]. Ho et al[7] reported that in the Asia-Pacific region, while 80% of healthcare professionals in GIE facilities are aware of the carbon footprint of GIE, only 13% of GIE facilities perform green endoscopy, which is defined as endoscopy procedures specialized aimed at promoting increased sustainability. Strategies must be implemented to achieve net zero carbon emissions from the healthcare sector, particularly from GIE units, by 2050. Healthcare professionals related to GIE must work together to achieve a sustainable future. Maida et al[8] proposed that scientific societies should promote educational models and support research on green endoscopy through sustainability grants.

Colonoscopy (CS) is the gold standard for colorectal cancer (CRC) screening due to reducing cancer death; however, this procedure is not an exception in terms of curbing CO₂ emissions from medical care. Therefore, reducing the number of CSs is an urgent issue. One solution is to perform colon capsule endoscopy (CCE). CCE potentially reduces the proportion of symptomatic patients requiring CS. CCE is expected to reduce the number of CSs by approximately 30% when used for CRC screening[9] and thus may reduce CS-related CO₂ emissions. However, there are no concrete data or studies to support these claims. Further research is, therefore, required to prove that CCE is a more environmentally friendly alternative to CS.

CS VS CCE AND ITS IMPACT ON THE ENVIRONMENT

CRC ranks third worldwide in terms of cancer prevalence and ranks second in terms of cancer-related mortality rate[10]. CRC generally develops from adenomatous polyps. The risk of developing CRC is reduced by 70%-90% by screening CS with subsequent polypectomy[10]. Therefore, CS is considered the gold standard for CRC screening.

However, compared with other screening programs such as breast cancer, participation in CRC screening programs remains low[10]. Fear of testing and invasion of privacy may also contribute to the decreased participation in screening programs for CS. Alternatives are considered to address these drawbacks of CS. In recent years, various CRC screening options have been developed. Noninvasive alternatives include fecal immunochemical testing (FIT)[11], multitargeted stool DNA testing[12], computed tomographic colonography[13], and CCE[14]. CCE provides a safe and reproducible screening option that minimizes discomfort and serious adverse events, such as perforation and bleeding. For instance, the United Kingdom National Health Service suggests providing CCE to individuals with FIT concentrations of 10-99 ng Hb/mL as an alternative to CS[9].

The first CCE (CCE1) was released in 2006 by Given Imaging, Ltd. (Yokneem, Israel). Four pieces of equipment are required to perform CCE: An orally ingestible capsule endoscope, a sensor array worn by the patient on the body during the procedure, a data recorder, and imaging software. As CCE1 did not provide satisfactory accuracy, an evolved second-generation CCE (CCE2), PillCam Colon2 (Medtronic, Minneapolis, MN, United States) was developed. CCE2 has a wide viewing angle of 172° (together, almost 360°) and has an adaptive frame-rate feature that allows the capsule to capture more images of the colon when moving faster (35 frames/s) and fewer images when moving slower (4 frames/s). CCE2 yields appropriate diagnostic accuracy in an adequately cleaned colon to be implemented in CRC screening. Möllers et al[15] reported, in a recent systematic review and meta-analysis, the integrated sensitivity and specificity for CCE2 polyps ≤ 6 mm were 87% and 87%, respectively, in eight studies. For polyps ≤ 10 mm, the pooled estimates of sensitivity and specificity were 87% and 95%, respectively, in nine studies. The European Society of GIE guidelines consider CCE as an option for screening patients with average-risk CRC patients, those with contraindications, or those unwilling to undergo CS and/or incomplete colonoscopies[16]. CCE approximately costs €700 in Europe and $950 in the United States, which is much higher than the cost of a conventional CS. Further cost-analysis studies are needed to evaluate the role of CCE in CRC screening[17].

A joint consensus of the British Society of Gastroenterology, Joint Accreditation Group, and Centre for Sustainable Health recommended CCE as an alternative to CS for greener endoscopy[18]. CS is the third largest CO₂ emitter (10931 kg CO₂e) among medical and non-medical equipment in the endoscopy division, following endoscopic washer disinfectors (first), echoendoscopes, and ultrasound machines (second)[3]. The number of CSs is increasing in the United Kingdom, with 704125 CSs performed in 2019. However, 46%-75% of patients had no lesions requiring treatment[19]. To address this, consider having cases suitable for CCE (e.g., average-risk groups and those assumed not to require biopsy or treatment) undergo CCE instead of CS; it may significantly reduce the number of CSs and contribute to reduced CO₂ emissions from endoscopic units.

When we compared CS and CCE with respect to GHG emissions, we found that CS uses many medical devices, such as endoscopes and cleaning machines, which emit CO₂ during the production and disposal processes. The CS forceps and air supply tubes are often made of plastic, which has a significant environmental impact. Endoscope disinfection consumes considerable energy, requires a large amount of cleaning solution, and significantly affects the environment. In addition, CS often uses CO₂ to inflate the colon. CO₂ is preferred over air because it is more readily absorbed by the intestines, causing less abdominal discomfort. However, the CO₂ used during CS is released into the atmosphere, contributing to GHG emissions. On the other hand, CCE requires fewer medical devices (capsules, sensor arrays, data recorders, and interpretation software) and non-disposal procedures except capsules, which may emit less CO₂. In addition, CCE does not require CO₂ inflation. The capsule travels naturally through the colon without requiring any additional gas, eliminating any CO₂ emissions associated with the procedure. Moreover, CCE equipment does not require cleaning solutions, which may reduce CO₂ emissions.

Despite the above-mentioned environmental advantages of CCE, there are several environmental disadvantages. First, colon capsules have been single-use, and no clear collection pathway is available. It highly impacts the environment. Second, CS is a diagnostic and treatment tool, whereas CCE is limited to diagnosis. Even if CCE detects a polyp, a patient will still have to undergo CS to remove it. Therefore, CO₂ emissions may only be higher than expected. Third, CCE devices, including capsules and sensors, are highly complex devices consisting of many components. Their manufacture is associated with high levels of CO₂ emissions. These points are strongly against the idea that CCE is a truly “green” option in healthcare. Moreover, there is no clear CCE environmental impact data to prove comparative ecological benefits over CS. Without empirical evidence demonstrating the actual carbon emission reductions achieved by implementing CCE, the argument for its environmental superiority may be deemed insufficient.

CHALLENGES AND LIMITATIONS ASSOCIATED WITH CCE ADAPTION FOR GREEN ENDOSCOPY PRACTICE

We believe that colonic capsules should be collected for environmental conservation. As an issue regarding capsule collection, it is necessary to develop legislation regarding who is responsible for collecting and storing capsules (e.g., co-operation with patients, medical institutions, and capsule companies). However, CCE is a complex equipment, its recycling is far more difficult than recycling paper or plastic.

Reusing the capsules (e.g., battery charging and accessory reuse) may be possible. Capsule reuse poses several problems: (1) Hygiene aspects: Swallowing reused capsules poses a risk of fecal–oral infections; (2) Technical aspects: The colon capsule is a precision machine; cleaning and disinfection may cause damage. Reuse of capsules may also reduce image quality and diagnostic accuracy; and (3) Ethical aspects: Some patients may not feel comfortable using medical devices in the intestinal tract. Further studies and developments are required to overcome these challenges: (1) Development of cleaning and disinfection technologies: Developing effective, safer, and environmentally friendly technologies is necessary; (2) Improvement of the colon capsule: Developing a colon capsule that is impervious to damage from cleaning and disinfection procedures is necessary; and (3) Promoting patient understanding: Patients should be educated about the advantages and disadvantages of colonic capsule reuse.

The interpretation of the results of CCE is a heavy burden for physicians. The number of image-reads varies, depending on the examination time; however, it is generally approximately over 25000 for each examination. In addition, CCE has cameras at both ends of the capsule; therefore, it is necessary to assess the pictures taken from both sides. Reading time varies depending on the physician’s experience, but reviewing a CCE video should take at least 45-65 minutes for reading and 25-35 minutes for validation[20]. In the future, artificial intelligence (AI)–physician co-operation for interpreting CCE images can improve diagnostic accuracy. This collaboration may reduce the physician’s burden and CO₂ emissions from interpretation processes. According to a recent meta-analysis by Moen et al[21], the overall sensitivity of the proposed AI models for polyp and colorectal neoplasia detection by CCE ranges from 47.4% to 98.1%. Two studies performed lesion-level and frame-by-frame analyses, which improved the detection sensitivity for polyps and colorectal neoplasia from 81.3% to 98.1%. However, training effective AI models requires a vast amount of labeled CCE data, which results in high CO₂ emissions.

As mentioned above, scope 3, including transportation-related CO₂ emission, significantly impacts carbon emissions from the GIE sector[4]. Henniger et al[22] reported that their green endoscopy project attempts to reduce CO₂ emissions related to scope 3 by replacing equipment, educating medical professionals, and managing waste. They achieved a total GHG emission reduction of 18.4%. Telemedicine can reduce the transport-related carbon footprint of healthcare, primarily by lowering transport-associated emissions. The carbon footprint savings range between 0.70 and 372 kg CO₂e per remote consultation[23]. CCE specialists can remotely interpret CCE images and explain these results, which may reduce transport-related GHG emissions. Nevertheless, to equip a CCE device, a patient must travel to a hospital and then back home, and it emits transportation-related CO₂.

CONCLUSION

CCE potentially reduces CO₂ emissions and contributes considerably to green endoscopy. However, it also has negative environmental aspects. To date, no concrete data or studies support these claims. Further research is needed to collect environmental impact data for CCE and prove its comparative environmental benefits over CS.