When this occurs, only very small portions of feces can pass this "tunnel." The rest is backed up and must wait and wait until it is possible to go through. Due to this "stop" in front of the "tunnel," bacteria start growing (bacteria thrive in a hot, dark and muggy environment, so this is a perfect place for bacteria to grow). This is one reason why a patient with adhesions may have bacterial overgrowth in the bowel. The reaction of the bowel when too many bacteria are present: diarrhea.