Rectal Cancer

BACKGROUND

Anatomy

The rectum is the lowest portion of the large intestine. It begins in the upper pelvis and ends at the anus. The rectum is approximately 5 inches long and lies within the muscular and fatty tissue of the pelvis. The blood supply of the upper two thirds of the rectum drains into the liver. This is why the liver is often the first site of spread of rectal cancer. There are lymph nodes immediately surrounding the rectum that drain into lymph nodes higher in the abdomen.

The wall of the rectum is made of muscle that is tubular in shape. This tube is lined by a mucosa, which is where cancers generally arise.

Epidemiology

There is increasing evidence that diet plays a role in the development of rectal cancer. In countries where red meat is popular, there is a high incidence of colon and rectal cancer. Conversely, in countries where a diet of starchy food with fiber is the norm, the incidence of these cancers is low.

There are other causes. Some cases of colon and rectal cancer are related to hereditary factors. Still others are related to inflammatory diseases of the colon such as ulcerative colitis.