Learn the primary and secondary ultrasound findings that indicate acute appendicitis.
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The diagnosis of acute appendicitis on ultrasound is based on direct visualization of the appendix with specific pathological features.
Measured outer wall to outer wall in the transverse plane. This is the most reliable primary criterion.
A normal appendix is compressible with graded compression. An inflamed appendix remains distended.
Echogenic focus with posterior acoustic shadowing within the appendix lumen.
Concentric rings in transverse view representing the thickened appendiceal wall layers.
Free fluid surrounding the appendix indicates inflammation or perforation.
Increased blood flow in the appendiceal wall indicates active inflammation.
Increased echogenicity of surrounding mesenteric fat.
Reactive lymph nodes in the right lower quadrant (>5mm).
A diagnosis of appendicitis requires visualization of the appendix with at least one primary criterion. Secondary signs increase diagnostic confidence but are not sufficient alone. When the appendix cannot be visualized, document secondary signs and consider second-line imaging.