Ileus, paralytic: Obstruction of the intestine due to paralysis of the intestinal muscles. The paralysis does not need to be complete to cause ileus, but the intestinal muscles must be so inactive that it prevents the passage of food and leads to a functional blockage of the intestine. Ileus commonly follows some types of surgery, especially abdominal surgery. It also can result from certain drugs, spinal injuries, inflammation anywhere within the abdomen that touches the intestines, and diseases of the intestinal muscles themselves. Irrespective of the cause, ileus causes constipation, abdominal distention, and nausea and vomiting. On listening to the abdomen with a stethoscope, few or no bowel sounds are heard (because the bowel is inactive). Also simply called ileus.