Mesenteric adenitis and acute terminal ileitis: US evaluation using graded compression.

One hundred seventy consecutive patients with clinical suggestion of acute appendicitis were studied by ultrasound (US) with the examiner using the graded compression technique. In 14 patients, the only US findings consisted of enlarged mesenteric lymph nodes in combination with mural thickening of the terminal ileum. This was consistent with the findings at surgery in four patients and with the results of barium studies in seven patients. In nine of 14 patients, stool cultures were performed, eight of which were positive for Yersinia enterocolitica. None of these 14 patients finally proved to have appendicitis. In a patient with acute pain in the right lower quadrant whose appendix cannot be visualized sonographically and whose US findings consist of enlarged mesenteric lymph nodes and mural thickening of the terminal ileum, the diagnosis is probably mesenteric adenitis and acute terminal ileitis. Appendectomy should be avoided in this condition.