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[Ultrasonography of the normal vermiform appendix].

AIM
To study the detectability and the appearance of the vermiform appendix with ultrasound in asymptomatic adults.


METHODS
A prospective study was performed on 300 patients, selected without regard to age, sex and weight. We tried to visualize the appendix with a 3.5 MHz annular array and a 5 MHz linear array transducer.


RESULTS
In 63% of the patients the appendix was clearly visualised. The main reasons for non-visualisation were obesity with insufficient ultrasound penetration (38%) and the caecum laying in pelvic or atypical position (24%). In 31%, no cause was apparent but we assume that the appendix often lies behind the caecum. The sonographic image showed an aperistaltic target originating at the caecum, and ending blindly. In 42% of cases the appendix was ovoid in transverse section; in 32%, round; and in 26% both forms were found within one appendix. Intraluminal gas was visible in 86%. The mean transverse diameter was 5.2 mm (min. 3 mm, max. 13 mm) and in 76% the transverse diameter was lower than 6 mm.


CONCLUSION
The sonographic detectability, the appearance and the size of the normal appendix show considerable variations.