This is from marvistavet.com, but it does go on to say that sometimes an animal must be put under anesthesia and have the stools manually removed.
One of the purposes of the colon (large intestine) is the storage of stool. Many pet owners become alarmed if the pet has not passed a stool in a few days, especially in a post-anesthetic situation. In fact, the colon can easily store several weeks worth of stool so if only a few days have passed it may be worthwhile to wait a little longer.
http://www.marvistavet.com/html/cons...megacolon.html