Presentation: Silent or symptomatic
The initial presentation of colorectal cancer may be either entirely asymptomatic or symptomatic. Symptoms of colon cancer may include diarrhea, abdominal discomfort, constipation, and sometimes, nausea. Other symptoms include a thin or flat stool. Fecal blood-occult or apparent-may be present. The stool may appear reddish, dark cranberry, or even black in color. Patients may experience pain caused by excessive gas trapped in the lower right abdomen. In advanced colon cancer, symptoms may include weight loss, pain in the abdomen caused by obstruction of the intestine, and loss of appetite.
Many patients — largely those with a primary tumor involving the right side of the colon — come to their doctor because of perceived "weakness," and are found to be anemic due to occult bleeding into the cecum.
More distal tumors in the sigmoid and rectum may result in obstruction or frank bleeding. Colonoscopy typically reveals very early tumor, especially when the tumor is in the distal colon or rectal region. Some tumors protrude into the lumen and may even be palpated during the digital rectal exam (DRE) when the patient performs a Valsalva's maneuver. However, the prognosis of the disease depends less on luminal protrusion and more on