From the Guidelines
Colon cancer can present with frank blood in stool, which appears as bright red or dark red blood visible to the naked eye, as stated in the study published in 2021 1. This bleeding occurs when tumors in the colon or rectum erode blood vessels, causing blood to mix with stool. However, not all colon cancers cause visible bleeding, and early-stage cancers may only produce occult (hidden) blood detectable through testing. Other common symptoms of colon cancer include:
- Changes in bowel habits
- Persistent abdominal discomfort
- Unexplained weight loss
- Fatigue The presence of frank blood in stool should prompt immediate medical evaluation, especially in individuals over 45 or those with risk factors such as family history of colorectal cancer or inflammatory bowel disease. It's essential to note that while frank blood can indicate colon cancer, it may also result from less serious conditions like hemorrhoids, anal fissures, or inflammatory bowel disease, as mentioned in the study published in 2004 1. Regardless of the presumed cause, visible blood in stool warrants prompt medical assessment to determine the underlying cause and appropriate treatment, and according to the study published in 2013 1, dark red rectal bleeding has a specificity of >95% for colon cancer. A complete medical history, physical examination, and laboratory tests, such as a complete blood count and coagulation assessment, should be performed to evaluate the severity of the bleeding and to correctly stratify the risk for each patient, as recommended in the 2021 study 1.
From the Research
Colon Cancer Symptoms
- Colon cancer can present with various symptoms, including rectal bleeding, as reported in a case study of a young pregnant woman diagnosed with metastatic rectal cancer 2.
- A prospective cohort study found that 'rectal bleeding' had a specificity of 99.4% and a positive predictive value (PPV) of 4.0% for colorectal cancer, indicating that rectal bleeding is a significant symptom of the disease 3.
- However, not all colon cancers present with frank blood in stool, as proximal colon cancers may not cause rectal bleeding at the initial consultation 3.
Diagnostic Approaches
- Colonoscopy is a crucial diagnostic tool for managing diverticular disease and colon cancer, and can be used to identify stigmata of recent hemorrhage (SRH) in diverticula 4, 5.
- Multitargeted stool tests, such as the ColoAlert™ test, can detect occult blood and human DNA in stool, which can be associated with the presence of colon cancer 2.
- A combination of symptoms, signs, and diagnostic tests, including faecal occult blood testing (FOBT) and anaemia, can increase the sensitivity of colon cancer diagnosis 3.