Brenda Spriggs, MD, MPH, MBA
Colon cancer is a potentially curable disease if it is caught in the early stages. This is the reason the American Cancer Society has recommended screening people starting at age 50. The symptoms of colon cancer vary according to location of the cancer within the colon as well as any spread outside the colon. The colon is divided into four main sections--ascending or right colon, transverse colon, descending or left colon, and the sigmoid colon. The sigmoid colon is considered a part of the left colon. The colonic contents travel from the small intestine up the ascending colon then along the transverse colon then down the descending colon and sigmoid before entering the rectum.
Ascending Colon Symptoms
Cancers in this part of the colon tend to go unnoticed for a long time. They may grow to quite large sizes before causing any symptoms. People with these malignancies may feel a mass in the right abdomen, have abdominal pain, fever, profuse sweating--especially at night--and anemia. The symptoms of anemia include weakness, easy fatiguability, shortness of breath and palpitations. These symptoms are explained by the anatomy of ascending colon. The ascending colon is wider than its descending counterpart, which allows for more growth of tumor before the tumor causes symptoms. Also the tumors that develop in the ascending colon tend to grow along the wall of the colon instead of directly outward into the lumen. Symptoms on the left side of the colon are usually caused by growth outward into the lumen, obstructing the flow of feces.
Descending Colon Symptoms
The symptoms of left-sided colon cancer are attributed the anatomy of that area of the colon. The lumen of the colon is smaller than that of its counterpart on the right and therefore the symptoms experienced are due to obstruction of the lumen. The primary symptom is a change in bowel habits. People experience increasing bouts of constipation. They may also notice a change in the caliber of the stool. The stool may also be coated with streaks of blood. Though these symptoms may also be seen in cancers in the right colon, they are most often seen in the left because the stool is more solid in the descending and sigmoid colon. The stool is still in liquid form in the ascending colon. Often, people with left-sided cancers present to the emergency room with a quartet of symptoms--abdominal pain, abdominal distention, vomiting and constipation. These are symptoms of bowel obstruction, a surgical emergency. This occurs when the lumen of the colon has been completely obstructed by cancer. The obstructed segment of the colon becomes markedly swollen and does not function as it should. Bowel obstruction may also be seen in right-sided cancers but is far more common on the left
Transverse Colon Symptoms
Cancer in the transverse colon has a mixture of the symptoms experienced in right and left colon due to the semi-solid nature of stool in this segment. People may experience some chronic pain and anemia along with intermittent constipation.