Outer diameter of the vermiform appendix as a sign of acute appendicitis: evaluation at US.
OBJECTIVE
To evaluate the usefulness and limitations of the outer diameter of the vermiform appendix at cross-sectional ultrasonography to confirm or rule out acute appendicitis.


METHODS
In a prospective study, outer appendiceal diameters in 240 control subjects and in 278 patients suspected of having acute appendicitis who did (n = 98) or did not (n = 180) have acute appendicitis were measured.


RESULTS
Outer appendiceal diameters in the control subjects ranged between 2 and 13 mm, and in 55 (23%) of 240 control subjects, diameters were 6 mm or more. Diameters in the symptomatic patients without acute appendicitis ranged between 2 and 11 mm, and 57 (32%) of 180 patients had diameters of 6 mm or more. Diameters of acutely inflamed appendices ranged between 6 and 30 mm. A diameter of 6 mm or more confirmed acute appendicitis with a sensitivity of 100%; a specificity of 68%; positive and negative predictive values of 63% and 100%, respectively; and an accuracy of 79%.


CONCLUSIONS
The outer appendiceal diameter of 6 mm or more as a sign of acute appendicitis provides high sensitivity but limited specificity. This diagnostic criterion is more useful in excluding acute appendicitis than in confirming it.
Rettenbacher
T
T
Departments of Radiology and Nuclear Medicine, Hospital Barmherzige Brueder, Salzburg, Austria. thomas.rettenbacher@uklibk.ac.at
Hollerweger
A
A
Macheiner
P
P
Rettenbacher
L
L
Tomaselli
F
F
Schneider
B
B
Gritzmann
N
N
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D001064:Appendicitis / Q000000981:diagnostic imaging*; D001065:Appendix / Q000000981:diagnostic imaging*; D002648:Child; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography