Findings supportive of the diagnosis of appendicitis include 5:
aperistaltic, non-compressible, dilated appendix (>6 mm outer diameter)
o
appears round when compression is applied
hyperechoic appendicolith with posterior acoustic shadowing
distinct appendiceal wall layers
o
implies non-necrotic (catarrhal or phlegmon) stage
o
loss of wall stratification with necrotic (gangrenous) stages 18
echogenic prominent pericaecal and periappendiceal fat
periappendiceal hyperechoic structure: amorphous hyperechoic structure (usually >10 mm) seen
surrounding a non-compressible appendix with a diameter >6 mm 11
periappendiceal fluid collection
target appearance (axial section)
periappendiceal reactive nodal prominence/enlargement
wall thickening (3 mm or above)
o
mural hyperemia with color flow Doppler increases the specificity 17
o
vascular flow may be lost with necrotic stages
alteration of the mural spectral Doppler envelope 16
o
may support diagnosis in equivocal cases
o
a peak systolic velocity >10 cm/s suggested as a cutoff
o
a resistive index (RI) measured at >0.65 may be more specific
Confirming that the structure visualized in the appendix is clearly essential and requires demonstration of it
being blind-ending and arising from the base of the cecum. Identifying the terminal ileum confidently is also
helpful.
A dynamic ultrasound technique using a sequential 3-step patient positioning protocol has been shown to
increase the detection rate of appendix 10. In the study, patients were initially examined in the conventional
supine position, followed by the left posterior oblique position (45° LPO) and then a “second-look” supine
position. Reported detection rates increased from 30% in the initial supine position to 44% in the LPO
position and a further increase to 53% with the “second-look” supine position. Slightly larger absolute and
relative detection rates were seen in children. The authors suggested that the effect of the LPO positioning
step improved the acoustic window by shifting bowel contents.
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