This has shown up on an x-ray of mine!! It seems as if it is a hardening of an artery? Maybe I am wrong.
this is a type of usually ureter stone a calcification following is a technical explaination.
Phleboliths, defined as focal calcified venous thrombi, are frequently seen along the normal anatomical course of the lower ureter. They are usually the result of injury to the vein wall commonly from venous hypertension and are composed of concentric calcified strata around a central kernel. Typically, phleboliths are rounded with a central lucency and are seen in the true pelvis often below the distal ureter. A limitation of a non-contrast CT is in the evaluation of stone disease when differentiating a pelvic phlebolith from a stone within the ureter, especially in patients with a paucity of retroperitoneal and pelvic fat. Circumferential periureteral edema, or the soft tissue "rim" sign, described as a rim of soft tissue attenuation seen around the circumference of an intraureteral calculus on non-contract CT, can also help differentiate ureteral calculi from phleboliths. Theoretically, phleboliths will not show a "rim" sign. Since larger stones result in stretching of the ureteral wall, the "rim" sign tends to be more commonly associated with the presence of smaller stones.