Graded-compression Ultrasound in acute appendicitis

Ultrasound has 85% sensitive and 92% specific with 78-96% accurate. Nondiagnostic study in 4% due to inadequate compression of RLQ. Useful in ovulating women (false-negative appendectomy rate in males 15%, in females 35%) + infants/children

Findings of acute appendicitis of ultrasound:

• Visualization of noncompressible appendix as a blind-ending tubular aperistaltic structure (seen only in 2% of normal adults, but in 50% of normal children)
• Laminated wall with target appearance of 6 mm in total diameter on cross section (81% SPECIFIC)/mural wall thickness 2 mm
• Lumen may be distended with anechoic/hyperechoic material
• Pericecal/periappendiceal fluid
• Increased periappendiceal echogenicity (= infiltration of mesoappendix/pericecal fat)
• Enlarged mesenteric lymph nodes
• Loss of wall layers = gangrenous appendix

Acute appendicitis at color Doppler US

False-negative US:

• Failure to visualize appendix
• Inability of adequate compression
• Aberrant location of appendix (eg, retrocecal)
• Appendiceal perforation
• Early inflammation limited to appendiceal tip

False-positive US:

• Normal appendix mistaken for appendicitis
• Alternate diagnosis: Crohn disease, pelvic inflammatory disease, inflamed Meckel diverticulum
• Spontaneous resolution of acute appendicitis

Color Doppler US:

• Increased conspicuity (= increase in size + number) of circumferential vessels in and around the wall of the appendix (= hyperemia)
• Decreased resistance of arterial waveforms
• Continuous/pulsatile venous flow
• Decreased/no perfusion = gangrenous appendicitis

Reference: Radiology Review Manual, The Radiolgy Assistant, RadioGraphics

Filed under: Acute Appendicitis, Gastrointestinal Emergency , Acute Appendicitis, Ultrasound