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 2) but may have a comet-tail sign.
This sign may be absent in cases of a larger (>4mm) or ureterovesical calculus 3.
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