Overview
From Adenomatous Polyp to Bowel Obstruction
Most colorectal cancers develop gradually from adenomatous polyps.
Most colorectal cancers develop gradually from adenomatous polyps. Over time, abnormal cells acquire malignant behavior, invade through the bowel wall, and may spread beyond the colon or rectum. A tumor can also narrow the bowel lumen. The colon is a hollow tube, so a growing mass may function like a clamp that progressively restricts stool and gas passage. Partial obstruction may cause cramping, abdominal distention, constipation alternating with loose stools, and a sensation of incomplete evacuation. Complete obstruction can produce severe distention, vomiting, inability to pass stool or flatus, and escalating pain. Bleeding may be visible as rectal blood, but it may also be occult. Slow blood loss can lead to iron-deficiency anemia, fatigue, exertional dyspnea, pallor, or tachycardia. New rectal bleeding or unexplained iron-deficiency anemia requires evaluation; do not assume hemorrhoids explain these findings without a diagnostic workup.