What are the signs of colorectal (colon) cancer?

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Last updated: May 30, 2025View editorial policy

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From the Guidelines

Colon cancer often presents with several key signs that should prompt medical attention, including changes in bowel habits, blood in the stool, abdominal pain or cramping, unexplained weight loss, fatigue, and a feeling that the bowel doesn't empty completely, as noted in the most recent guidelines 1.

Key Signs and Symptoms

  • Changes in bowel habits (persistent diarrhea or constipation)
  • Blood in the stool (either bright red or dark, tarry stools)
  • Abdominal pain or cramping
  • Unexplained weight loss
  • Fatigue
  • A feeling that the bowel doesn't empty completely
  • Narrow stools
  • Anemia due to chronic blood loss
  • Persistent gas and bloating These symptoms develop because cancerous growths in the colon can bleed, obstruct normal bowel function, and cause inflammation.

Importance of Early Detection

It's essential to note that early-stage colon cancer may produce no symptoms at all, which is why regular screening is crucial, particularly after age 45 or earlier for those with family history or other risk factors, as recommended by recent clinical guidelines 1. Any persistent change in bowel habits lasting more than a few weeks should be evaluated by a healthcare provider, as early detection significantly improves treatment outcomes.

Evaluation and Diagnosis

According to the latest clinical guidelines 1, the diagnosis of postoperative recurrence of colon cancer should involve clinical symptoms, physical signs, digital rectal exam, blood CEA and CA199 level, colonoscopy, pelvic enhanced MRI, and contrast-enhanced thoracoabdominal CT. Don't dismiss rectal bleeding as just hemorrhoids without proper medical evaluation, as it can be a sign of colon cancer, and early detection is critical for improving treatment outcomes 1.

From the Research

Signs and Symptoms of Colon Cancer

The provided studies do not directly discuss the signs and symptoms of colon cancer. However, they do provide information on screening and treatment options.

Screening for Colon Cancer

  • The U.S. Multi-Society Task Force on Colorectal Cancer recommends screening for colon cancer starting at age 50 years in average-risk persons, except in African Americans in whom limited evidence supports screening at 45 years 2.
  • The recommended screening tests include colonoscopy every 10 years and annual fecal immunochemical test (FIT) 2.
  • Other screening options include CT colonography every 5 years, the FIT-fecal DNA test every 3 years, and flexible sigmoidoscopy every 5 to 10 years 2.

Treatment of Colon Cancer

  • The standard adjuvant treatment of colon cancer is fluorouracil plus leucovorin (FL), which can be improved by adding oxaliplatin 3.
  • Colonic polyps, which are considered precursors of colon cancer, can be treated with excisional biopsy techniques such as snare polypectomy, endoscopic mucosal resection (EMR), and endoscopic submucosal dissection (ESD) 4.
  • The choice of treatment modality depends on the size and features of the polyp, as well as the risk factors for invasive malignancy 4.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Colonic Polyps: Treatment.

Clinics in colon and rectal surgery, 2016

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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