Ball of wool sign (hydatid cyst)

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.

Inspired signs

Article information

rID: 49542
Section: Signs
Synonyms or Alternate Spellings:
  • Spin sign
  • Whorl sign
  • Congealed water lily sign
  • Yarn sign

ADVERTISEMENT: Supporters see fewer/no ads

Cases and figures

  • Case 1
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.