Bloody or vrey dark stools are a concerning symptom often associated with advanced stages of colorectal cancer, though they can also indicate other gastrointestinal issues. This article provides verified data about this symptom and the disease stage in which it commonly appears, as of January 16, 2026.
What is Stage III Colorectal Cancer?
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Stage III colorectal cancer signifies that the cancer has spread beyond the initial tumor and has involved nearby lymph nodes, but has not yet metastasized to distant organs. According to the American cancer Society, Stage III is further divided into three sub-stages (IIIA, IIIB, and IIIC) based on the extent of lymph node involvement and whether the tumor has grown into nearby organs.
Detail: The staging system, developed by the American College of Surgeons Commission on Cancer, is crucial for determining treatment options and predicting prognosis. Stage III cancers are generally considered treatable, but require a multi-modal approach, often including surgery, chemotherapy, and sometimes radiation therapy.
Example: A patient diagnosed with Stage IIIB colon cancer might have a tumor that has grown through the colon wall and into nearby organs, with involvement of 6-15 regional lymph nodes.
Symptoms Common in Stage III Colorectal Cancer
While symptoms can vary, Stage III colorectal cancer often presents with more pronounced and persistent symptoms than earlier stages.
- Changes in bowel habits: This includes diarrhea, constipation, or a change in the consistency of stool.
- Abdominal discomfort: Persistent cramping, gas, or pain.
- Rectal bleeding: This can manifest as bright red blood in the stool or darker, tarry stools.
- Unexplained weight loss: Significant weight loss without intentional dieting.
- Fatigue: Feeling unusually tired or weak.
Bloody or Dark Stools and Colorectal Cancer
Bloody or very dark stools (melena) are frequently observed in Stage III colorectal cancer due to the tumor bleeding into the digestive tract.
Detail: The appearance of blood in the stool depends on where in the colon or rectum the bleeding originates. Bleeding higher up in the colon tends to result in darker,tarry stools as the blood has been digested. Bleeding closer to the rectum usually causes bright red blood. however, the presence of blood in the stool does *not* automatically mean cancer; it can also be caused by hemorrhoids, diverticulitis, or other conditions.
Example: A Mayo Clinic report states that approximately 50% of patients with Stage III colon cancer report experiencing rectal bleeding at some point during their illness.
When to Seek Medical Attention
Any persistent change in bowel habits or the presence of blood in the stool warrants a prompt medical evaluation.
Detail: Early detection is critical for improving treatment outcomes in colorectal cancer. The Centers for Disease Control and Prevention (CDC) recommends regular screening tests, such as colonoscopies, starting at age 45 for individuals at average risk. Individuals with a family history of colorectal cancer or other risk factors may need to begin screening earlier.
Example: If a person experiences rectal bleeding accompanied by abdominal pain and unexplained weight loss, they should consult a physician immediately for diagnostic testing, such as a colonoscopy and biopsy.
