A case of Crohn's disease limited to the appendix, showing a portentous ultrasonographic finding.

A case of Crohn's disease limited to the appendix is reported. A preoperative ultrasonic study of the lower right abdomen revealed an interesting appearance that we named the "milky way sign." Microscopic findings in the resected specimen confirmed that the sign represented adipose tissue of the mesoappendix that had become involved by transmural inflammation. This seems to be highly suggestive of Crohn's disease.