Sonographic appearance of the normal appendix in adults.

OBJECTIVE To evaluate the sonographic visualization of the normal adult appendix, a large series of sonographic images from consecutive asymptomatic patients was analyzed. METHODS A total of 788 consecutive adult patients (402 male and 386 female; median age +/- SD, 51.1 +/- 17.2 years; range, 16-91 years) were examined by appendiceal transabdominal sonography with tissue harmonic imaging. The detection rate, outer appendiceal diameter, intraluminal content, and location of the appendix were estimated. The overall normal appendix was separated into appendix-visualized and appendix-not-visualized groups, which were then examined for the relationship with abdominal wall thickness, body mass index (in kilograms per square meter), age, and sex. RESULTS The normal appendix was detected in 388 (49.2%) of 788 patients. The outer appendiceal diameter +/- SD was 4.27 +/- 1.2 mm (range, 1.0-11.1 mm). In 291 (75%) of the 388 patients, appendices could be depicted in the intra-luminal gas during sonography. The location of the appendix was classified according to the appendiceal tip, which was found to be abdominal in 37 (9.5%), pelvic in 291 (75%), retrocecal in 23 (6.0%), and a midline extension in 37 (9.5%). In both body mass index and abdominal wall thickness, significant differences were found between appendix-visualized and appendix-not-visualized cases (P < .05). There was no significant difference in age (P = .37) or sex (P = .23) between appendix-visualized and appendix-not-visualized cases. CONCLUSIONS The results show that the normal adult appendix can be revealed by sonographic visualization in a large series of asymptomatic patients.