Risks of Colorectal Cancer Screening Tests

Serious bleeding or a hole or tear in the colon happens after a stool test in about 0.3 out of 1,000 people (or about 3 out of 10,000 people). This is not from the stool test itself, but from the follow-up colonoscopy or surgery after a positive stool test. A tear or serious bleeding from sigmoidoscopy happens in about 0.8 out of 1,000 people (or about 8 out of 10,000 people). Serious problems from a colonoscopy happen in about 2.6 out of 1,000 people (or about 26 out of 10,000 people).

Chart based on Warren JL, et al. (2009). Adverse events after outpatient colonoscopy in the Medicare population. Annals of Internal Medicine, 150(12): 849–857. DOI: 10.7326/0003-4819-150-12-200906160-00008. Accessed February 2, 2015. & Rabeneck L, et al. (2008). Bleeding and perforation after outpatient colonoscopy and their risk factors in usual clinical practice. Gastroenterology, 135(6): 1899–1906. DOI 10.1053/j.gastro.2008.08.058. Accessed February 13, 2015.

Screening tests have some risk of creating a hole or tear (perforation) in the colon. There is also a chance of bleeding. Both of these risks are small.

Current as of: May 1, 2026

Author: WebMD Ignite Staff
Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

Current as of: May 1, 2026

Author: WebMD Ignite Staff

Clinical Review Board
All WebMD Ignite education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

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