<prompt> A 24-year-old man is brought to the emergency room with symptoms of acute intestinal obstruction. His temperature is 38degC 101degF, respirations are 25 per minute, and blood pressure is 12080 mm Hg. Physical examination reveals a mass in the right lower abdominal quadrant. At laparoscopy, there are numerous small bowel strictures and a fistula extending into a loop of small bowel. Which of the following is the most likely diagnosis?AdenocarcinomaCarcinoid tumorCrohn diseasePseudomembranous colitis  <response>: Crohn disease is a transmural, chronic inflammatory disease that may affect any part of the digestive tract. Intestinal obstruction and fistulas are the most common intestinal complications of Crohn disease. Occasionally, free perforation of the bowel occurs. The risk of small bowel cancer is increased at least threefold in patients with Crohn disease. Pseudomembranous colitis choice D and ulcerative colitis choice E are not associated with fistula formation. Adenocarcinoma choice A rarely, if ever, arises in the terminal ileum.Diagnosis: Crohn disease 