Doctors are warning that certain stool shapes and colors, such as narrow and bloody poops, could be a sign of colorectal cancer, which is spreading rapidly among young people in the US.

According to the health body, this process can give rise to a "change in the shape of the stool". Typically, the change takes the form of very narrow stools, it says. Other warning signs include ...

Normal stool is typically one to two inches in diameter, whereas narrow pencil stool is almost flat, and has a stringy appearance. A colon stricture tends to be a sign of narrowing or obstruction ...