GlossarySee Full Entry

Rectum: The rectum is defined as the distal large intestine commencing opposite the sacral promontory and ending at the upper border of the anal canal. When measured from below with a rigid sigmoidoscope, it extends 16 cm from the anal verge. A tumor is classified as rectal if its lower margin lies 16 cm or less from the anal verge, when measured from below with a rigid sigmoidoscope. The rectum may be subdivided into three parts according to the distance of the lower margin of the tumor from the anal verge (assessed by rigid sigmoidscopy) * Upper third/upper rectum 12-16 cm * Middle third/middle rectum 6-< 12 cm * Lower third/lower rectum <= 6 cm

Alternate Names
Extraperitoneal portion of the large intestine
Lower rectum
Rectal ampulla
Primary Site
C209 Rectum