this is the symptom you should not ignore

He colorectal cancer, traditionally associated with older peoplehas shown an alarming increase in young adults under 50 years of age. Recent studies indicate that early-onset diagnoses are on the rise, especially in patients who present with symptoms such as rectal bleeding, even without a family history.

Recent data indicate that certain factors, such as history of smoking either genetic markers, They can influence the risk, but the presence of specific symptoms significantly multiplies the probability of detecting the disease.

Rectal bleeding: an early warning symptom

Researchers of the University of Louisville (United States), have presented an investigation in the Clinical Congress 2025 of the American College of Surgeons (ACS) in Chicago, from October 4 to 7, which warns of rectal bleeding after observing that it can be a predictor of colon cancer in those under 50 years of age, but what was thought.

Researchers found that adults younger than 50 who undergo a colonoscopy have a significantly increased risk of colorectal cancer when the procedure is performed after surgery. alert of rectal bleeding.

Specifically, they observed that rectal bleeding increases the likelihood of a colorectal cancer diagnosis by 8.5 times, underscoring the need to take this symptom seriously even without a family history in a population that would not otherwise meet the age criteria for screening.

It is a small analysis with reliable results

The retrospective study analyzed 443 patients under the age of 50 who underwent colonoscopy in 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 I see have no family history,” said lead author Dr. Sandra Kavalukas, a colorectal surgeon at the University of Louisville School of Medicine in Louisville.

“This research supports the question of who does or does not justify a colonoscopy: if a person under the screening age presents with rectal bleeding, they should seriously consider a colonoscopy,” says the researcher.

Thus, according to the work, the vast majority (88%) of patients who were subsequently diagnosed with early-onset colorectal cancer underwent a colonoscopy due to symptoms, such as bleeding, compared to just over half (55%) of patients without cancer.

Most of the cancer patients were ex-smokers.

On the other hand, only 13% of cases of early-onset colorectal cancer presented a marker frequently associated with hereditary syndromes, such as genetic alterations present in some colorectal cancers. A family history of colorectal cancer, while a factor, was only associated with a twofold increase in the odds.

Additionally, patients diagnosed with early-onset colorectal cancer were also significantly more likely to be former smokers (almost twice as likely).

In this way, the study aims to help doctors decide which young, symptomatic patients would benefit from undergoing diagnostic colonoscopy.

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

The study addresses the gap in youth care

Thus, the findings address a critical gap in care for young adults, who are not eligible for routine screening but have the fastest growing rates of colorectal cancer. The study provides data supporting coverage of diagnostic colonoscopies in young symptomatic patients. The research team is now working on a broader analysis with the goal of creating a risk score calculator.

Common symptoms of colorectal cancer

Colorectal cancer can present a variety of symptoms that, depending on the World Health Organization (WHO)include changes in bowel habits such as diarrhea, constipation or thinner stools; blood in the stool, which may appear bright red or very dark; persistent abdominal pain or distension; unexplained weight loss; constant fatigue; and low iron levels that can lead to anemia.

Recent research from the National Cancer Institute (NCI) indicates that in adults under 50 years of age, the most common warning signs are abdominal pain, rectal bleeding, persistent diarrhea, and iron deficiency anemia. The presence of one or more of these symptoms can significantly increase the probability of a diagnosis of early-onset colorectal cancer, which is why specialists recommend seeing a health professional as soon as possible if any of these signs occur. The early detection is key to improve treatment outcomes and survival.