Colonoscopy Risk Should be Considered When Evaluating Benefit Over

Armen Hareyan's picture

The risks associated with colonoscopy should be considered when evaluating its incremental benefit over less invasive screening tests, according to researchers from Kaiser Permanente and the Centers for Disease Control and Prevention (CDC). The study, "Complications of Colonoscopy in an Integrated Health Care Delivery System," appears in the current issue of Annals of Internal Medicine.

Researchers identified patients receiving colonoscopy and followed them for 30 days for evidence of hospitalization for procedure-related complications.

During colonoscopy, precancerous polyps can be removed and biopsies can be done on tissue samples. The rate of complications following colonoscopy, even colonoscopy without biopsy, is higher than for other colorectal cancer screening tests, including flexible sigmoidoscopy, according to Theodore Levin, MD, a Kaiser Permanente clinician and researcher and the lead author of the study.

"Delayed bleeding was not uncommon, suggesting that patients should be advised about their risk and that screening centers should have follow-up procedures in place to monitor delayed complications," he said.

Over 60 percent of the post-polyp removal bleeding episodes occurred in patients with polyps smaller than one centimeter, the ones least likely to become cancer or develop into a serious problem, said Levin. "Being able to better define which polyps are high risk before removing them, would make colonoscopy a substantially safer procedure," he said, explaining that techniques to accomplish this continue to improve.


The researchers examined a large sample of community practice gastroenterologists with systematic follow-up within the Kaiser Permanente system. This is important because most prior estimates of colonoscopy complications have come from referral centers or closely monitored clinical trials, which have limited the ability to generalize results to community practice. In addition, a previous study of ambulatory centers relied on the self-report of complications, possibly underestimating them and was unable to evaluate post procedure bleeding.

"The systematic follow-up in this study allowed us to look at post procedure bleeding and also those cases where its occurrence was delayed," said Levin.

In this study, researchers relied on automated data of Kaiser Permanente, Northern California, an integrated-delivery health care system. Colonoscopy was used to follow up other tests or to conduct surveillance in people with personal or family history of colorectal cancer. Few were performed as the primary screening test.

Additional researchers who collaborated on the study include Wei Zhao, MPH; Carol Cornell, PhD, both with the Kaiser Permanente Division of Research in Oakland, CA; Laura C. Seeff, MD, and Jean A. Shapiro, PhD, both with the Centers for Disease Control and Prevention; Diane L. Manninen, PhD, and Jane Schulman, PhD, of the Batelle Memorial Institute, Seattle, WA and Crystal City, VA.

The study was funded by the Centers for Disease Control and Prevention.

The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, DOR's 400-plus staff is working on more than 250 epidemiological and health services research projects.