Young adults with rectal bleeding linked to 8.5 times higher risk of colorectal cancer

A 2023 American Cancer Society found that colorectal cancer cases among young adults increased from 11% in 1995 to 20% in 2019 – Image credit American College of Surgeons

CANCER DIGEST – Oct. 5, 2025 – Patients under age 50 who undergo colonoscopy to investigate rectal bleeding have been found to have 8.5 times the risk of colorectal cancer, a new study shows. The findings suggest that the symptom of rectal bleeding in this patient population needs to be taken seriously even in the absence of a family history.

The study was presented at the American College of Surgeons (ACS) Clinical Congress 2025 in Chicago, Oct. 4-7.

The U.S. Preventive Services Task Force guidelines recommend screening colonoscopy starting at age 45 for most people without a family history of colorectal cancer. This study provides further support for that recommendation as the rates of colorectal cancer have been rising steadily in this age group since the 1990s, according to the National Institutes of Health.

The researchers led by senior author Sandra Kavalukas, MD, FACS of the University of Louisville School of Medicine analyzed colonoscopy data from 443 patients under 50 between 2021 and 2023. Of those patients 195 (44%) were diagnosed with early-onset colorectal cancer, and the remaining 248 (56%) had normal results.

“This research lends support to the question of who does or doesn’t warrant a colonoscopy," Kavalukas said in a press release, "if you have a person below the screening age with rectal bleeding, you should seriously consider a colonoscopy.” 

The analysis also showed that the vast majority (88%) of patients later diagnosed with early-onset colorectal cancer underwent colonoscopy due to symptoms such as rectal bleeding, compared to 55% of non-cancer patients. In addition, only 13% of early onset colorectal cancer had a family history or genetic markers for the disease. Finally, early onset colorectal cancers were significantly more likely to be smokers or former smokers.

The goal of this study was to help clinicians decide whether to refer younger patients for diagnostic colonoscopy.

“If they’re 35 and they come in with rectal pain, they probably don’t need a colonoscopy,” Dr. Kavalukas explained. “But if they come in with a bleeding complaint, they are 8.5 times more likely to have a colorectal cancer.”

Sources: American College of Surgeons press release