The gas-containing appendix: potential sonographic pitfall in the diagnosis of acute appendicitis.

The presence of gas within the appendix on plain abdominal radiographs is nonspecific and may or may not be associated with acute appendicitis. This finding, however, has not previously been reported with graded compression sonography of the right lower quadrant. Gas within the appendix was identified in four of 154 patients with a visualized appendix. All four patients had surgically confirmed acute appendicitis. Diagnostic difficulties were encountered in three of these four patients. In two patients, the findings were misinterpreted as an extraluminal gas-forming periappendiceal abscess. In an additional patient, the gas-filled appendix was initially mistaken for a segment of normal terminal ileum. The gas-filled appendix is a potential pitfall in the sonographic diagnosis of acute appendicitis. However, if other diagnostic criteria are met, gas within the appendix should not preclude establishing a sonographic diagnosis of appendicitis.