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Onion peel sign

Last revised by Dr Daniel J Bell on 17 Dec 2017

The onion peel sign (also called the Cumbo sign or double arch sign) is a feature seen with complicated pulmonary hydatid cyst in which the gas lining between the endocyst and pericyst has the appearance of an onion peel. It is pathognomonic for a ruptured hydatid cyst.

History and etymology

It was first described by Cumbo in 1921 2.

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