[Ultrasonography of normal vermiform appendix]

The aim of this study was the detection and visualisation of the normal vermiform appendix and its characteristics by ultrasonography in adults with no clinical suggestion of acute or chronic abdominal disease. A prospective study was performed in 200 subjects. The graded-compression ultrasonography technique was used to explore the lower right quadrant of the abdomen and the pelvis. The examination was performed using a 4 MHz sector array and 7.5 MHz linear array transducer. In a few cases, a 10 MHz linear array transducer was used. The appendix was visualized in 54% of patients. In all cases where the appendix was visualized it was found to be either on the ileo-psoas muscle or directly beneath the abdominal wall. The ileo-caecal valve was visualized in 78% of cases. The transverse diameter was found to be no greater than 6.5 mm except in three cases that had a diameters ranging from 7 to 9 mm. Diameter variability along the length of the same appendix was demonstrated in 5% of subjects. Wall thickness was no greater than 2.5 mm. Our experience suggests that graded-compression ultrasonography is a valuable procedure for detecting the vermiform appendix more frequently than has been previously reported. The patients physical constitution and the anatomical location of the vermiform appendix were found to be important factors affecting the ability to visualize the vermiform appendix. The ability to visualise the normal vermiform appendix ultrasonographically supports the clinical diagnosis and excludes acute appendicitis.