Von Sinner described a number of findings seen on imaging studies performed on a patient with echinococcosis. Two (serpent and spin) signs are diagnostic of echinococcosis, and are useful when other findings are ambiguous or falsely negative. The author is from King Faisal Specialist Hospital in Riyadh, Saudi Arabia.
Features of the serpent (snake) sign:
(1) Undulating appearance seen on ultrasonography, CT or MRI.
(2) There is rupture of the endocyst membrane (secondary to cyst damage or degeneration) while the pericyst membrane is still intact.
Features of the spin (whirl) sign:
(1) Twirled, gyrated or twisted appearance seen on MRI.
(2) It is associated with collapse of parasitic membranes. There may be spillage of cyst contents through a defect in the wall.
If either of these findings are seen then echinococcosis can be diagnosed with confidence.
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