Where does obstruction occur in cases of colorectal cancer?

• A. Right side
• B. Left side
• C. Transverse colon
• D. Rectum

Answer: (B)

Colorectal cancer is most commonly associated with obstructive symptoms when the tumor is located on the left side of the colon, particularly in the sigmoid colon and the rectum. This section of the colon is narrower compared to the right side and is more likely to lead to obstruction when a tumor develops.

Left-sided tumors typically present with symptoms such as changes in bowel habits, narrower stools, and abdominal pain due to the obstruction. Tumors on the right side or in the transverse colon are less likely to cause a complete obstruction because of the wider diameter of the lumen and the typical presence of liquid stool that can pass around or through the mass. In contrast, rectal tumors can also cause obstruction, but they are typically classified under left-sided tumors due to their close proximity to the sigmoid colon.

In summary, when considering the likelihood and mechanism of bowel obstruction in colorectal cancer, left-sided tumors are the most characteristic culprits due to their anatomical configuration and symptomatology.