When C. difficile bacteria gets into an individual's digestive system, it can begin to reproduce and colonize in these tissues. The bacteria invade the large intestinal lining and tissues as it grows. They cause extensive damage to the lining of the colon. This damage results in swelling and inflammation in the large intestine, which can progress into raw patches of tissue that produce pus and bleed. The nerves in the smooth muscle tissues that make up the intestines become irritated by the inflammation and swelling. The irritated nerves transmit pain signals to the brain, which causes patients to feel pain in their abdomen. The irritated nerves also induce the inappropriate and abnormal contraction of the smooth muscles that surround and form the organs of the digestive tract. This produces abdominal cramps.