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Erschienen in:
15.02.2018 | Classics in Abdominal Radiology
The onion skin sign of appendiceal mucocele
Erschienen in: Abdominal Radiology | Ausgabe 9/2018
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Mucocele is a broad term describing accumulation of mucinous secretions within the appendiceal lumen secondary to various non-neoplastic and neoplastic processes. While some sonographic features of an appendiceal mucocele were first described in 1981 by Li [1], the onion skin descriptor was coined in 2002 by Dgani [2]. The onion skin sign refers to the sonographic appearance of an appendiceal mucocele where concentric layers of echogenic layering debris are seen within an enlarged and elongated appendix (Fig. 1), resembling the appearance of an onion in cross section (Fig. 2). Notably, this layering appearance is not seen on CT (Fig. 1).
Fig. 1
Appendiceal mucoceles in two different patients seen on Ultrasound (A, C) with CT correlate (Star in B, D). Multiple crescentic layers of echogenic debris are seen within both enlarged appendixes (arrows), demonstrating the onion skin sign. Note that, onion skin is only a sonographic sign, with no evidence of the layering phenomenon on CT
Fig. 2
Cross section view of a red onion demonstrating its multiple layers. Photo taken by author, Sergey Leshchinskiy, MD
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