A study giving new insight into the effectiveness of colonoscopy suggests that while it reduces the risk of death from colorectal cancer by 60% to 70%, instead of up to 90% as previously thought, yet, it is useful for detecting cancer, especially on the left side of the colon.  The reason why it is useful in detecting cancer on the left side rather more than on the right, is because it is harder to examine the right side of the colon.  The other reason is that the stool is more liquid on the right side and coating the lining, it makes it difficult to see the polyps.
 
In addition, experts say cancer on right side of the colon is not only harder to examine, it is also differs from cancer on the left side.  According to Dr. Heinz Lenz, Professor of Medicine at Keck School of Medicine and Norris Comprehensive Cancer Centre at USC, they are like two different diseases.  While, left side polyps are generally mushroom-shaped, projecting outwards on a stalk, right side polyps are flatter, with no stalk, the reason why polyps on the left are easier to detect and remove.
 
Besides, though most colorectal cancers develop from polyps, there are others that develop directly from the lining of the colon, more often the case on the right side.  As well, bloody stool, a characteristic symptom of colorectal cancer doesn’t happen with cancer on the right side, wherein, the only symptoms are abdominal discomfort or pain.  Which is why doctors recommend colonoscopy for patients with these complaints.
 
As the quality of colonoscopies improves, they are a highly effective weapon against colorectal cancer, the third most common cancer in the United States , and the second most deadly, after lung cancer.  Despite limitations, it would be disastrous if doctors recommended fewer colonoscopies and according to experts, colonoscopy is still among the best ways to save lives from colorectal cancer.