USC Department of Colorectal Surgery
USC Department of Colorectal Surgery
The Function of the Rectum

"What do I need to know about the function of the rectum?"

The function of the rectum is to store the stool until it is socially convenient to eliminate it. The rectum, therefore, needs to have a capacity (volume), and a compliance (easily distendable). If it does not have a capacity and compliance, then the stool cannot easily wait, and the pressures in the rectum are high, often higher than the anal canal pressures. This can result in urgency to bowel movements and incontinence.

The anal muscles function as an outlet resistance and a plug. In recent years, the function of these muscles has been more clearly characterized and the relationship between the reservoir function of the rectum and the outlet obstruction of the anal canal has been identified as being the primary mechanisms of bowel control. It is a complex relationship and one that may be important during the removal of rectal cancers. Growths or abnormalities in the most distal 15 centimeters are called rectal (rectal polyp, rectal cancer), and those above are called colonic.

 

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