Colorectal cancer is the third leading cause of cancer-related deaths in Thailand, and its incidence is increasing every year. Often dubbed a “silent killer,” many patients fail to notice its early signs—only discovering it once the disease has progressed. However, colorectal cancer does send out warning signals. By being observant and proactive, early detection and timely treatment are possible.
What Causes Colorectal Cancer?
Colorectal cancer occurs when abnormal cells develop in the large intestine, which is approximately 150–180 cm long, starting from the junction with the small intestine to the rectum. It typically begins as a small polyp in the lining of the colon. If detected early, it can often be completely cured.
5 Key Warning Signs That May Indicate Colorectal Cancer
1. Family History of Colorectal Cancer
Having a family member with colorectal cancer increases your risk by two to three times. However, about 80% of patients have no family history. Even those at higher risk can lower their chances through healthy lifestyle choices—eating a fiber-rich diet, avoiding constipation, and limiting grilled, fried, or high-fat foods. Regular health check-ups and annual cancer screenings are highly recommended.
2. Chronic Constipation
Many people dismiss constipation as minor, but chronic constipation may indicate an underlying intestinal issue such as inflammation or irritable bowel syndrome. If lifestyle changes like improving your diet and increasing water intake don’t help, you should see a doctor promptly.
3. Blood or Mucus in Stool
This is a key red flag. If you regularly notice mucus or blood mixed with stool, it’s a sign that something may be wrong in your colon. Additionally, abnormally thin stools can also indicate a possible blockage. In either case, a doctor’s evaluation is crucial.
4. Unexplained Weight Loss
Sudden weight loss despite eating the same as usual—especially without exercising—can be a serious warning sign. If you experience this, consult a doctor immediately, as it may indicate a significant internal issue like cancer.
5. Irregular Bowel Habits (Alternating Constipation and Diarrhea)
Frequent switching between diarrhea and constipation without relief may suggest early-stage colorectal cancer. If this happens despite eating freshly cooked food and making dietary adjustments, seek medical evaluation.
Who Is at Risk of Colorectal Cancer?
The major risk factor remains genetics, accounting for 60–70% of cases. Another 10–15% stem from lifestyle factors, including:
- High consumption of red meat
- Eating preserved or processed foods
- Exposure to nitrosamines (found in some preserved foods)
People with a family history of colorectal cancer under age 60 are at higher risk. One common complication is colonic obstruction, seen in around 90% of colorectal cancer cases. Causes of blockage include inflammation, infections, or in rare cases, twisting of the colon. As the tumor grows, it narrows the colon’s passage, causing:
- Constipation
- Inability to pass gas
- Abdominal bloating
- Cramps or pain
- Vomiting
- Loss of appetite
