On unenhanced CT KUB, a small calcific opacity is seen at the right vesicoureteric junction. Which accompanying finding best distinguishes a ureteric calculus from a phlebolith at this location?

• A Central lucency within the opacity
• B Soft tissue rim of oedematous ureteric wall surrounding the opacity ✓
• C Tail of linear soft tissue extending from the opacity
• D Absence of proximal hydroureteronephrosis

Explanation

The soft tissue rim sign represents oedema of the ureteric wall wrapped around an impacted calculus and favours a stone over a phlebolith. The comet tail sign, a linear soft tissue strand extending from the focus, favours a phlebolith, as does a central lucent centre. Phleboliths are typically more peripheral and rounded, whereas a stone usually causes some degree of proximal dilatation when acutely obstructive.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.