Ultrasonography of appendicitis

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Author: Mikael Häggström [notes 1]

Choice of initial exam

In suspected appendicitis:

  • Ultrasonography is the first choice of exam. In children, it gives a proper diagnosis in the vast majority even in obese children.[1] In adults, it is often inconclusive, but is still recommended as a first imaging choice when symptoms indicate the condition.[2] If inconclusive, further evaluation can be done by reassessment by the clinician, as well as complementary imaging with MRI or CT.[2]
  • CT of appendicitis is the preferable initial method in the elderly, who are less likely to develop adverse effects from the radiation dose.[3] It is also indicated as initial exam in adults with more non-specific acute abdominal symptoms.


Ultrasound of a normal appendix for comparison
A normal appendix without and with compression. Absence of comprehensibility indicates appendicitis.[4]
  • Evaluate without and with compression.
  • If possible, follow it from end to end for complete evaluation.
  • Evaluate lymph nodes, mainly along the iliac vessels and aorta
  • Look for ascites at least in the recto-uterine or recto-vesical pouch.

Finding the appendix

A high frequency probe is preferable in children. The external iliac vessels are helpful in initial orientation, as the appendix is often located in their vicinity. Look for a relatively small tubular structure. When finding such a structure, exclude mimics, mainly:

  • Juxtaposing serosal layers, may mimic a longitudinal section of an appendix, but will not turn circular when rotating the probe 90°.
  • Blood vessels, mainly external iliac and inferior epigastric vessels, will show pulsations in Doppler mode.

Findings indicating appendicitis

  • Absence of compressibility[5]
  • Dilatation >6 mm in outer diameter[5]
  • Appendicolith[5]
  • Distinct wall layers[5]
  • Hyperechoic and prominent periappendiceal and pericecal fat[5]
  • Periappendiceal fluid[5]
  • Target sign[5]
  • Periappendiceal lymphadenopathy[5]

If no pathologic appendix

If the appendix is normal or cannot be clearly visualized, consider performing:


  • Location of the appendix is important when surgery may be needed. At least when atypically located, the description should include both area in relation to surface landmarks, as well as relation to internal structures, particularly the cecum.
  • Findings as per above, or negation of signs of appendicitis.
  • Presence/Absence of ascites or any visible lymphadenopathy, also helpful in differential diagnosis

If the appendix is normal or cannot be clearly visualized, preferably also report:

  • Even the absence of hydronephrosis, at least for the right side.
  • Even the absence of increased wall thickness of the gallbladder and/or gallbladder stones.
See also: General notes on reporting


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.


  1. George A Taylor, David E Wesson. Acute appendicitis in children: Diagnostic imaging. UpToDate. Retrieved on 2018-06-25. Last updated Apr 30, 2018
  2. 2.0 2.1 Mostbeck, Gerhard; Adam, E. Jane; Nielsen, Michael Bachmann; Claudon, Michel; Clevert, Dirk; Nicolau, Carlos; Nyhsen, Christiane; Owens, Catherine M. (2016). "How to diagnose acute appendicitis: ultrasound first ". Insights into Imaging 7 (2): 255–263. doi:10.1007/s13244-016-0469-6. ISSN 1869-4101. 
  3. Hui, Thomas T.; Major, Kevin M.; Avital, Itzhak; Hiatt, Jonathan R.; Margulies, Daniel R. (2002). "Outcome of Elderly Patients With Appendicitis ". Archives of Surgery 137 (9). doi:10.1001/archsurg.137.9.995. ISSN 0004-0010. 
  4. Reddan, Tristan; Corness, Jonathan; Mengersen, Kerrie; Harden, Fiona (March 2016). "Ultrasound of paediatric appendicitis and its secondary sonographic signs: providing a more meaningful finding ". Journal of Medical Radiation Sciences 63 (1): 59–66. doi:10.1002/jmrs.154. 
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Dan J Bell and Koshy Jacob. Appendicitis. Radiopaedia. Retrieved on 2018-06-25.