Comet tail sign (phleboliths)

The comet tail sign (in urological imaging) is helpful in distinguishing a ureteric calculus from a phlebolith and strongly favors the latter.

The sign refers to a tail of soft tissue extending from a calcification, representing the collapsed/scarred/thrombosed parent vein. When well seen, it is said to have a positive predictive value of 100% .

See also