Doughnut sign (missed testicular torsion)

Last revised by Dr Ali Alsmair on 16 Mar 2022

The doughnut sign, also known as the bull's-eye, halo or ring sign, is the name of a distinctive appearance of a missed testicular torsion on scrotal scintigraphy

In a missed torsion (i.e. established testicular infarction), there is a reactive hyperperfusion of the ipsilateral dartos muscle enveloping the testis, leading to this distinctive doughnut appearance on the scintigram. It is not a pathognomonic appearance as an identical appearance may be seen with a large testicular abscess or mass. However, in the clinical context of likely delayed diagnosis of torsion, in which sonographic findings are equivocal, it may be invaluable.

Conversely, when an earlier torsion is present, focal photopenia is seen in the affected hemiscrotum without the doughnut sign of reactive increased blood flow.

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