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Ball of wool sign (hydatid cyst)

Last revised by Dr Ayla Al Kabbani ◉ on 01 Feb 2020

Citation, DOI & article data

Citation:

Khader.O.Thabet, M., Al Kabbani, A. Ball of wool sign (hydatid cyst). Reference article, Radiopaedia.org. (accessed on 18 Aug 2022) https://doi.org/10.53347/rID-49542

DOI:

https://doi.org/10.53347/rID-49542

Permalink:

https://radiopaedia.org/articles/49542

rID:

49542

Article created:

28 Nov 2016 by Dr Mohammed Al Khader.O.Thabet

Revisions:

7 times by 6 users - see full revision history

Systems:

Gastrointestinal, Chest

Section:

Signs

Tags:

hydatid disease, cases

Synonyms:

Spin sign
Whorl sign
Congealed water lily sign
Yarn sign

The ball of wool sign, also referred to as the yarn sign or congealed water lily sign, is an ultrasound appearance, representing degeneration of hydatid cysts (WHO class CE 4). The inner side of the cyst detaches from the cyst wall and folds on itself, causing a change from anechoic (fluid) to a solid, hyperechoic appearance without internal septations or daughter cysts ⁴.