Phleboliths are uncommon forms of lithiasis that occur in venous structures.
A phlebolith occurs when there is dystrophic calcification of thrombus within a vein or venous malformation.
The deposition of calcium carbonate and calcium phosphate is laminated giving an "onion skin" appearance.
On angiography there is a radio-opaque center (from recanalization of the thrombus) surrounded by the calcification.
Appearance on ultrasonography: mobile echogenic shadow within a hypoechoic vessel
Appearance on MRI:
(1) well-defined T1 and T2 weighted mixed signal intensity lesion
(2) hypointense calcific speck within the lesion on T2-weighted images
Phleboliths are seen after thrombosis in vein with low blood flow:
(1) arteriovenous malformations
(2) hemangiomas
(3) other veins and venules
On the perioral region thay may be mistaken for sialoliths.
