soft-tissue rim sign
The soft-tissue rim sign is used to distinguish a ureteric calculus from a phlebolith. The former appears as a calcific density with a surrounding rim of soft tissue which represents the edematous ureteric wall. Phleboliths on the other hand usually have imperceptible walls (although up to 8% may have a soft tissue rim sign ) but may have a comet-tail sign.
This sign may be absent in cases of a larger (> 4 mm) or ureterovesical calculus .