How does a colonoscopy work and how often should you get one?

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1. 1

   Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

   New England Journal of Medicine (Bretthauer et al.)Published Oct 9, 2022Checked Oct 17, 2026

   “Follow-up data were available for 84,585 participants in Poland, Norway, and Sweden - 28,220 in the invited group, 11,843 of whom (42.0%) underwent screening, and 56,365 in the usual-care group. A total of 15 participants had major bleeding after polyp removal. No perforations or screening-related deaths occurred within 30 days after colonoscopy. During a median follow-up of 10 years, 259 cases of colorectal cancer were diagnosed in the invited group as compared with 622 cases in the usual-care group. In intention-to-screen analyses, the risk of colorectal cancer at 10 years was 0.98% in the invited group and 1.20% in the usual-care group, a risk reduction of 18% (risk ratio, 0.82; 95% confidence interval [CI], 0.70 to 0.93). The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual-care group (risk ratio, 0.90; 95% CI, 0.64 to 1.16). In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colonoscopy than among those who were assigned to no screening. (Funded by the Research Council of Norway and others; NordICC ClinicalTrials.gov number, NCT00883792.).”

2. 2

   Stress-Testing US Colorectal Cancer Screening Guidelines: Decennial Colonoscopy from Age 45 is Robust to Natural History Uncertainty and Colonoscopy Sensitivity Assumptions

   Medical Decision Making (Lima et al.)Published Apr 29, 2025Checked Oct 17, 2026

   “Strategies in which screening starts at age 50 y with 10-y intervals were never efficient, saving fewer life-years than starting screening at age 45 y and performing colonoscopies every 15 y while requiring more colonoscopies per person.ConclusionsDecennial colonoscopy screening initiation at age 45 y remained a robust recommendation. Colonoscopy screening with a 10-y interval starting at age 50 y did not result in an efficient use of colonoscopies in any of the scenarios evaluated.HighlightsColorectal cancer colonoscopy screening strategies initiated at age 45 y were projected to yield more life-years gained while requiring the least number of colonoscopies across different model assumptions about disease natural history and colonoscopy sensitivity.Colonoscopy screening starting at age 50 y with a 10-y interval consistently underperformed strategies that started at age 45 y.”

3. 3

   Population-Based Colonoscopy Screening for Colorectal Cancer

   JAMA Internal Medicine (Bretthauer et al.)Published May 23, 2016Checked Oct 17, 2026

   “Of 31 420 eligible participants randomized to the colonoscopy group, 12 574 (40.0%) underwent screening. Participation rates were 60.7% in Norway (5354 of 8816), 39.8% in Sweden (486 of 1222), 33.0% in Poland (6004 of 18 188), and 22.9% in the Netherlands (730 of 3194) (P < .001). The cecum intubation rate was 97.2% (12 217 of 12 574), with 9726 participants (77.4%) not receiving sedation. Of the 12 574 participants undergoing colonoscopy screening, we observed 1 perforation (0.01%), 2 postpolypectomy serosal burns (0.02%), and 18 cases of bleeding owing to polypectomy (0.14%). Sixty-two individuals (0.5%) were diagnosed with colorectal cancer and 3861 (30.7%) had adenomas, of which 1304 (10.4%) were high-risk adenomas. Detection rates were similar in the proximal and distal colon. Colonoscopy screening entails high detection rates in the proximal and distal colon. Participation rates and endoscopist performance vary significantly. Postprocedure abdominal pain is common with standard air insufflation and can be significantly reduced by using CO2. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00883792.”

4. 4

   Outcomes of Screening Colonoscopy in Older Adults: A Large Propensity-Matched Real-World Cohort Study.

   JGH open : an open access journal of gastroenterology and hepatology (Shakarchi et al.)Published Oct 4, 2026Checked Oct 17, 2026

   “Colonoscopy increased polyp detection (HR 4.43 [95% CI 4.15-4.73] at 30 days; 1.88 [1.82-1.95] at 5 years) and colorectal cancer detection (4.56 [3.62-5.74]; 1.78 [1.59-1.98]; all p ≤ 0.003). Five-year all-cause mortality was unchanged (HR 1.01 [0.97-1.05]; p = 0.741). Perforation rose at 5 years (HR 1.29 [1.02-1.63]; p = 0.033); gastrointestinal bleeding fell at 1 year (HR 0.90 [0.84-0.97]; p = 0.004). After exclusion of pre-index anemia (70 399 pairs), 5-year HRs remained 1.72 for polyps and 1.52 for cancer. In an indication-restricted cohort also excluding fecal abnormalities, weight loss, abdominal pain, and change in bowel habit (54 300 pairs), the 5-year HRs were 1.59 and 1.32. Subsequent colonoscopy from day 31 to year 5 was not more frequent after index screening (5.8% vs. 6.2%; HR 0.93).ConclusionScreening colonoscopy improved polyp and cancer detection but did not reduce 5-year all-cause mortality. The late perforation signal was not explained by more subsequent or therapeutic colonoscopy. Decisions after age 75 should be individualized.”

5. 5

   Clinical practice Guidelines: quality of colonoscopy in colorectal cancer screening

   Endoscopy (Jover et al.)Published Mar 21, 2012Checked Oct 17, 2026

   “Goals of this clinical practice guidline: Collecting the evidence about the quality of colonoscopy screening for colorectal cancer (CRC) in order to serve as a tool for screening programs, endoscopy units and endoscopists that perform screening colonoscopies. Defining and establishing quality indicators and minimum requirements based on available evidence that endoscopy units and endoscopists involved in CRC screening programs should meet. Providing evidence about procedures that may improve the quality of colonoscopy.”

6. 6

   Colorectal Cancer Screening and Health-Related Social Needs in a National Sample of US Adults.

   JAMA network open (Ewing et al.)Published Apr 1, 2026Checked Oct 17, 2026

   “The proportion up to date with CRC screening was 63.91% (9758 adults) overall and increased with age, from 31.01% (586 adults) among adults aged 45 to 49 years to 64.24% (4539 adults) among those aged 50 to 64 years, and 80.85% (4633 adults) among those aged 65 to 75 years. In adjusted models, housing instability (aOR, 0.82; 95% CI, 0.67-0.99) and transportation barriers (aOR, 0.78; 95% CI, 0.64-0.95) were associated with lower odds of being up to date with CRC screening. Screening odds declined with increasing number of unmet HRSNs, including among adults reporting 1 unmet need (aOR, 0.84; 95% CI, 0.72-0.98). Associations were most pronounced among adults aged 50 to 64 years, among whom housing instability (aOR, 0.77; 95% CI, 0.61-0.97), transportation barriers (aOR, 0.71; 95% CI, 0.56-0.91), and reporting 1 HRSN (aOR, 0.80; 95% CI, 0.66-0.97) were associated with lower odds of being up to date with screening.Conclusions and relevanceIn this cross-sectional study, unmet HRSNs were associated with lower CRC screening uptake, particularly among adults aged 50 to 64 years. Addressing HRSNs may support age-specific strategies to improve CRC screening.”