byAmerican College of Surgeons

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Adults under 50 undergoing colonoscopy were found to have a dramatically higher risk of having colorectal cancer when the procedure was done for rectal bleeding. Researchers found that rectal bleeding increased the odds of a colorectal cancer diagnosis by 8.5 times, underscoring the need to take the symptom seriously even in the absence of a family history in a population who may not otherwise meet screening age criteria.

The research was presented at the American College of Surgeons (ACS)Clinical Congress 2025, held in Chicago, October 4–7.

Theretrospective studyanalyzed 443 patients under 50 who underwent a colonoscopy at the University of Louisville Health System between 2021 and 2023. Of them, 195 (44%) were diagnosed with early-onset colorectal cancer, while 248 (56%) had normal results.

"Many of the early-onset colorectal cancers that I see have no family history," said senior author Sandra Kavalukas, MD, FACS, a colorectal surgeon at the University of Louisville School of Medicine in Louisville, Kentucky.

"This research lends support to the question of who does or doesn't warrant a colonoscopy: if you have a person below the screening age withrectal bleeding, you should seriously consider a colonoscopy."

The study aims to help clinicians decide which young, symptomatic patients would benefit from undergoing a diagnostic colonoscopy.

"If they're 35 and they come in with rectal pain, they probably don't need acolonoscopy," Dr. Kavalukas explained. "But if they come in with a bleeding complaint, they are 8.5 times more likely to havecolorectal cancer."

The findings address a critical gap in care foryoung adultswho are not eligible for routine screening but are experiencing thefastest-rising rates of colorectal cancer. The study provides data to support coverage for diagnostic colonoscopies in symptomatic young patients.

The U.S. Preventive Services Task Force guidelines recommend screening colonoscopies starting at age 45 for most people without afamily historyof the disease.

The research team is now working on a larger analysis with the goal of creating a risk score calculator.

More information: Kavalukas S, et al. Risk Factors and Indicators for Early Onset Colorectal Cancer: A Retrospective Analysis, Scientific Forum, American College of Surgeons (ACS) Clinical Congress 2025.

Provided by American College of Surgeons