Estimating Harms Associated with Screening Colonoscopy: Insights for Clinicians

For more than 2 decades, the United States Preventive Services Task Force ( USPSTF ) and other national organizations have recommended colorectal cancer screening, with colonoscopy being one of 4 options for colorectal cancer screening. Although serious harm is known to occur as a result of screening colonoscopy, the USPSTF concluded that the risk of harm is outweighed by the potential benefits, depending on the patient’s age, risk factors, and prior colonoscopic findings, as long as Colonoscopy is performed at the recommended frequency for at-risk adults between 45 and 75 years of age.

Complications associated with screening colonoscopy can be due to bowel preparation, anesthesia, and the procedure itself. Serious harms include intestinal perforation and bleeding requiring hospitalization, as well as infections, cardiovascular events and death. This serious damage can be reduced with good colonoscopic technique, but cannot be completely avoided.

In recent years, the recognition that some patient harm is inevitable has increased attention to the concept of “preventable harm . ” At the same time, there has been growing recognition that “low-value care ,” or medical services that are unnecessary or inappropriate, should be viewed as a source of preventable patient harm. 6The authors conducted this systematic review of the annual rate of serious harm secondary to screening colonoscopy with the intention of using the results for a future study, which will estimate the rates of preventable harm from inappropriate colonoscopy. This study differs from previous systematic reviews in 2 ways: it aims to assess harms exclusively in the context of screening, as opposed to diagnostic colonoscopy, and includes harms that commonly develop days or weeks after the procedure.

Aim:

This study aims to comprehensively evaluate the direct and serious harms of screening colonoscopy in the United States. While other researchers have completed systematic reviews estimating the harms of all types of colonoscopy, this analysis focuses on screening colonoscopies that had adequate follow-up to avoid underestimating late harms.

Data sources:

PubMed and Embase were queried for relevant studies on the harms of screening colonoscopy published between January 1, 2002 and April 1, 2022.

Study selection:

English-language studies of screening colonoscopy for average-risk patients were included. Studies must have followed patients for an adequate time after the procedure, defined as 30 days after colonoscopy.

Main results:

The primary outcome was the number of episodes of major bleeding and gastrointestinal (GI) perforations within 30 days of screening colonoscopy.

Results:

A total of 1951 studies were reviewed for inclusion; 94 were reviewed in full text. Of those reviewed in their entirety, 6 studies, including a total of 467,139 colonoscopies, met the inclusion criteria and were included in our analysis of harms related to screening colonoscopies.

The rate of major bleeding credibly ranged from 16.4 to 36.18 per 10,000 colonoscopies; the perforation rate ranged credibly from 7.62 to 8.50 per 10,000 colonoscopies.

Conclusion

Understanding and reducing harm is a common goal of doctors and health systems. We conducted a rigorous analysis of the harms that occurred in the course of screening colonoscopy, which is the third most common cancer screening procedure in the US, surpassed only by Pap tests and mammography.

Recently, a publication in the New England Journal by Bretthauer et al. suggested that the mortality benefits of screening colonoscopy have been overestimated in cohort studies. The authors cited a more accurate estimate of harms from this screening tool as relevant to the health system and individual decision making. 21In Bretthauer’s publication, bleeding was cited as a complication of screening colonoscopies and occurred when polypectomies were performed.

Patients should consider the impact of irregular findings when considering screening mechanisms. Our study is unique in that it includes only studies that had at least 30 days of follow-up , used similar definitions for significant harms, and provided data on completed colonoscopies for screening indications specifically.

Our harm estimates are higher than those of the USPSTF, which lists the risk of serious bleeding from screening colonoscopy as 2 in 10,000 procedures (95% CI, 0.7-4 in 10,000; I 2 = 52.5%) and the risk of perforation 1 in 10,000 procedures (95% 0.4-1.4 in 10,000; I 2 = 18.4). This difference may be due to the shorter follow-up period of the studies included in their analysis: the USPSTF review included eligible studies regardless of the length of the follow-up period.

In the studies we reviewed, the vast majority of complications occurred after the first 72 hours , resulting in a higher damage estimate than the working group. The increased risk from 2/10,000 to 16.4/10,000 for hemorrhage and from 1/10,000 to 7.6/10,000 for perforation appears to be a significant burden for the patient. As such, the conversation doctors have with patients must be adjusted to address this increased risk. As age increases, the risk usually increases as well; some literature reviewed provided age-adjusted results, but without consistency. The risk-benefit ratio may remain constant as people age because the risk of colorectal cancer increases, as does the concurrent risk of harm.

A recent systematic review from the American Society of Gastroendoscopists (ASGE) provides an estimate of harms due to screening colonoscopy that is similar to ours. That review cites approximately 24 hemorrhages per 10,000 procedures (95% CI, 24 to 25) and 5.8 perforations per 10,000 procedures (95% CI, 5.7 to 6.0). In subgroup analysis, ASGE did not identify a difference in harm rates between screening versus diagnostic colonoscopy.

A wide range of harms were found in the literature review. This may be due to the lack of standard measures for colonoscopy complications and the variety of reporting methods. Not all colonoscopy complications have the same consequences for the patient, the hospital, and the healthcare system. A metric for analyzing harms that would further help identify the true rate would include patient-reported harms versus physician-identified harms; a severity scale (such as the degree of hypovolemia, the intensity of pain, or the development of advanced disease); and whether intervention was required, such as utilization of the Emergency Department post-procedure; hospitalizations secondary to the procedure; and mortality. Although current electronic medical records (EMR) may limit the specific link between the index procedure and complications.

In a future analysis, this team will evaluate the impact of harms on the general population in the context of overuse of screening colonoscopy. Screening colonoscopy is likely overused, as cited by Djinoban, 2019 and in our own recent systematic review. Harms in the context of overuse place patients at unnecessary and potentially preventable risk.

Summary

Despite limitations in data on rates of harm related to screening colonoscopy, it is possible to estimate a credible range of rates. Additional research on standardization of metrics and harm reporting may reduce the size of this range, allowing for better discussion between clinicians and patients about potential screening options.

Patients should be actively involved during decision making regarding colon cancer screening; The type of screening a patient chooses should be based on her or his personal risk factors, goals, and values. In a future study, we will estimate the rate of harm incurred during colonoscopy overuse.