Signs & Symptoms

What are the common signs and symptoms of colorectal cancer?

Common signs and symptoms of colorectal cancer include:

  • bright red or very dark blood in the stool
  • a change in the frequency of bowel movements
  • constipation, or a feeling that the bowel doesn’t empty completely
  • stools that are narrower than usual
  • general abdominal discomfort, such as frequent gas pains, bloating, and/or cramps 
  • weight loss with no known reason
  • constant tiredness
  • vomiting

Colorectal cancer does not usually produce symptoms early in the progress of the disease. Symptoms are dependent upon the site of the primary tumor. Cancers of the proximal colon tend to grow larger than those of the left colon and rectum before producing symptoms.

As the tumor expands in the intestinal lumen (the space in the interior of a tubular structure), such as the intestine, abnormal vasculature and trauma from the fecal stream may result in bleeding. Typically, blood is mixed in with the stool and may not be obvious to the patient (occult bleeding). Patients may develop iron deficiency anemia. Alternatively, tumors of the anus, sigmoid colon, and rectum may give rise to hematochezia, blood in the stool that is readily apparent.

As colon cancer grows, several symptoms may appear. Obstruction of the colonic lumen may produce symptoms of abdominal distension, pain, nausea, and vomiting. Obstruction of the gastrointestinal tract suggests a large tumor and a poorer prognosis.

Other symptoms of colorectal cancer may suggest an invasive process. Invasive tumors can penetrate the muscularis propria and invade adjacent tissue. This results in pain and may initiate symptoms specific to the site of invasion: tenesmus is produced by tumor invasion into the rectum; bladder penetration may produce urinary symptoms such as pneumaturia; pelvic invasion may produce perineal or sacral pain; and colonic perforation may result in an acute abdominal pain.

Some tumors produce a wasting syndrome, cancer cachexia, characterized by loss of appetite, weight and strength. The wasting occurs despite the fact that most patients with colorectal cancer do not have hypermetabolic (the physiological state of having a greatly increased rate of metabolic activity) energy expenditure. Cancer cachexia is common in patients with advanced gastrointestinal malignancies. 

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