Imaging modalities for diagnosis of appendicitis

	Advantages	Disadvantages
US	No ionizing radiation	Lower diagnostic accuracy than CT or MRI
	Widely available, including at the bedside	Patient- and operator-dependent variability in diagnostic performance
		High rates of indeterminate examinations with 50 to 85% of normal appendices not visualized^[1,2]
CT	High diagnostic accuracy	Ionizing radiation
CT	Lowest rates of indeterminate examinations with 80 to 90% of normal appendix visualized^[3,4,5]	Intravenous iodinated contrast needed for optimum diagnostic performance
MRI	No ionizing radiation	Limited availability
	High diagnostic accuracy	Requires patient to lie still in an enclosed scanner for 10 to 30 minutes
	Moderate rates of nondiagnostic examinations with 20 to 30% normal appendices not visualized^[6]

US: ultrasound; CT: computed tomography; MRI: magnetic resonance imaging.

References:

Yabunaka K, Katsuda T, Sanada S, Fukutomi T. Sonographic appearance of the normal appendix in adults. J Ultrasound Med 2007; 26:37.
Williams R, Shaw J. Ultrasound scanning in the diagnosis of acute appendicitis in pregnancy. Emerg Med J 2007; 24:359.
Benjaminov O, Atri M, Hamilton P, Rappaport D. Frequency of visualization and thickness of normal appendix at nonenhanced helical CT. Radiology 2002; 225:400.
Nikolaidis P, Hwang CM, Miller FH, Papanicolaou N. The nonvisualized appendix: incidence of acute appendicitis when secondary inflammatory changes are absent. AJR Am J Roentgenol 2004; 183:889.
Johnson PT, Horton KM, Kawamoto S, et al. MDCT for suspected appendicitis: effect of reconstruction section thickness on diagnostic accuracy, rate of appendiceal visualization, and reader confidence using axial images. AJR Am J Roentgenol 2009; 192:893.
Nikolaidis P, Hammond N, Marko J, et al. Incidence of visualization of the normal appendix on different MRI sequences. Emerg Radiol 2006; 12:223.

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