1. Change in Bowel Habits
A persistent change in bowel habits is one of the most common early signs of colon cancer. This can include diarrhea, constipation, or a noticeable difference in the frequency or consistency of your stools lasting more than a few weeks. Colon tumors can partially block the bowel, causing disruptions in normal stool passage.
What to watch for specifically:
- Sudden onset of constipation or diarrhea without an obvious cause
- Alternating constipation and diarrhea
- Stools that are loose or watery more often than usual
- Changes lasting longer than four weeks
Because these symptoms overlap with many benign conditions like irritable bowel syndrome or infections, it’s important to monitor their duration and progression. If you notice persistent changes in your bowel habits, especially if you are over 50 or have risk factors like a family history of colorectal cancer, consult your healthcare provider promptly.
2. Blood in Stool
Blood in the stool is a critical warning sign that should never be ignored. In colon cancer, bleeding often occurs due to tumor ulceration or irritation of the bowel lining. This blood may be visible as bright red streaks on the stool or toilet paper, or it may be hidden (occult) and only detected through laboratory testing.
Types of stool blood to be aware of:
- Bright red blood: Typically indicates bleeding from the lower colon or rectum.
- Dark or tarry stools: May indicate bleeding higher in the colon.
- Occult blood: Not visible but detected by fecal immunochemical tests (FIT) or stool guaiac tests, commonly used in colon cancer screening.
Visible blood should prompt an urgent evaluation, including colonoscopy, to identify the source and rule out malignancy, as early-stage colon cancer can bleed intermittently.
