Maria, 52 years old, noticed that over the past two months her bowel function had changed. Sometimes constipation, sometimes the opposite, and one day she noticed a little blood on the toilet paper. She thought it was hemorrhoids and kept putting it off. She only saw a doctor when she began to feel exhaustion that didn't go away with rest.

"The data and clinical case cited in this article are fictional and are merely illustrative, serving to facilitate understanding of the topic addressed."

Stories like this repeat quite often, because intestinal cancer (also called colorectal cancer) usually gives signs well before it is diagnosed. The problem is that many of these signs seem "too normal" to draw attention. According to the National Cancer Institute (INCA), this type of cancer is the third most common in Brazil, and the estimate is more than 53,000 new cases per year between 2026 and 2028. Understanding the warning signs is the first step toward seeking help at the right time.

The first signs that appear in the bathroom

The intestine "tells stories" through what comes out of it, and that is where the first warnings usually appear:

  • Blood in the stool. It can be bright blood, red, or darker. Many people confuse it with hemorrhoids (and sometimes it is), but bleeding that repeats itself deserves evaluation.
  • Change in the shape of the stool. Thinner stools, in ribbon format, persistently, may indicate a narrowing in the intestine.
  • Change in bowel habits. Constipation or diarrhea that appear out of nowhere and continue for more than two or three weeks, especially if they are different from the pattern the person always had.
  • Sensation that the intestine did not empty completely, even after bowel movements.

One important point: none of these signs, in isolation, means that the person has cancer. Hemorrhoids, fissures, irritable bowel syndrome, and diet also cause similar symptoms. What deserves attention is persistence: symptoms that return, that have no clear explanation, or that last longer than a month.

The first signs that appear in daily life

In addition to what happens in the bathroom, intestinal cancer can also manifest itself more discreetly in daily life:

  • Fatigue that does not improve with rest, often linked to anemia (decrease in the number of red blood cells) caused by bleeding that the person didn't even notice.
  • Weight loss with no apparent reason, without changes in diet or exercise routine.
  • Recurrent abdominal pain or discomfort, like cramping, that comes and goes.
  • Sensation of bloating or persistent abdominal swelling.

These signs tend to be even more nonspecific than those in the bathroom, and for this reason they go unnoticed more easily. A recent survey by the A.C. Camargo Cancer Center showed that, even among those who noticed blood in their stool, almost half did not see a doctor right away. And an important fact: these signs deserve evaluation at any age, not just after age 50, since cases among younger people have been increasing.

How diagnosis works

The first step, even without symptoms, is screening, that is, looking for the disease before it shows signs. The entry exam is the fecal occult blood test (the SUS is incorporating the immunochemical version, more accurate and without dietary restrictions, expected for the second half of 2026). This test identifies blood that is not visible to the naked eye.

If the result comes back altered, or if the person already has symptoms, the next exam is colonoscopy. In it, a thin tube with a camera travels through the entire large intestine, allowing direct visualization of the intestinal wall, identification of polyps (lesions that can become cancer over time) and their removal at the same time, when possible. There are also other options, such as sigmoidoscopy and tomographic colonography (the "virtual colonoscopy"), used in specific situations.

When there is confirmed suspicion, imaging exams (tomography, magnetic resonance) and blood tests complement the investigation to understand the extent of the disease and plan treatment.

Who should start screening, and when

The Ministry of Health recommendation for the SUS is to begin screening at age 50. Other guidelines, including international recommendations adopted since 2021, already indicate starting at age 45, because of the increase in cases in younger people. Those with a family history of colorectal cancer or polyps, or inflammatory bowel diseases, usually need to start earlier, and this should be discussed individually with a doctor.

Risk factors

Some factors increase the chance of developing the disease:

  • Age above 45 to 50 years
  • Family history of colorectal cancer or intestinal polyps
  • Inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis
  • Diet rich in ultra-processed foods, processed meats, and cured meats
  • Sedentary lifestyle
  • Obesity
  • Smoking
  • Excessive alcohol consumption

Having one or more of these factors does not mean the person will develop cancer, but it helps the doctor determine if screening should start earlier.

What can be done to reduce risk

The good news is that much of the risk can be addressed in daily life:

  • Prioritize natural foods, with plenty of fiber (fruits, vegetables, legumes, whole grains)
  • Reduce consumption of ultra-processed foods and processed meats
  • Maintain regular physical activity
  • Avoid cigarettes
  • Moderate alcohol consumption
  • Maintain weight within a healthy range
  • Don't put off screening, since it can detect and remove polyps before they become cancer

When to see a doctor

Bleeding in the stool, persistent change in bowel habits, unexplained weight loss, or unusual fatigue lasting more than two or three weeks are sufficient reason for a consultation. There is no need to wait for the symptom to "worsen" to seek help, and the sooner the investigation starts, the simpler the path to diagnosis and treatment tends to be.

This content is informative and educational in nature and does not replace medical consultation, diagnosis, or treatment. Always seek a healthcare professional to evaluate your case individually.

Dr. Rebeca Soares Andrade CRM - GO 39335