Colorectal cancer usually begins as a small polyp and grows slowly; early stages are often silent. When warning signs appear they typically reflect tumor size, location, and bleeding. Key symptoms include:
- Persistent change in bowel habits
Alternating constipation and diarrhea, narrower pencil-shaped stools, or sudden urgency that lasts more than a few weeks. - Blood in or on the stool
Bright-red coating, dark maroon mixed blood, or occult bleeding detected only by testing; hemorrhoidal bleeding is usually fleeting and separate. - Abdominal discomfort
Cramping, gas pain, bloating, or a feeling of incomplete evacuation; right-sided tumors may cause vague aching while left-sided lesions classically provoke colicky pain. - Unexplained weight loss & fatigue
Losing >5 kg without dieting, together with anemia-related tiredness or pallor, suggests chronic blood loss and systemic disease. - Rectal mass sensation or pain on sitting
Low tumors can create a permanent feeling of fullness or discomfort in the pelvic floor. - Signs of complications
Acute complete obstruction causes distension, vomiting, and absence of flatus; perforation adds severe pain and fever.
Any new combination of altered bowels plus bleeding, iron-deficiency anemia, or weight loss warrants prompt colonoscopy and imaging.
| Symptom | Typical Features | Red-flag Clues |
|---|---|---|
| Bowel change | Constipation/diarrhea >4 weeks | Pencil-thin stools |
| Bleeding | Mixed dark blood or coating | Persistent, unexplained |
| Cramps | Colicky RLQ/LLQ, bloating | Night pain, distension |
| Weight | >5 kg drop, anorexia | With fatigue, anemia |
| Rectal | Urgency, tenesmus, sitting pain | Palpable mass on exam |
| Obstruction | No flatus, vomiting | Surgical emergency |