Phlebolith

On X-ray imaging, phleboliths present as focal calcifications, visualized as small, rounded, radio-opaque foci with a presence of central lucency. This feature demonstrates moderate sensitivity and high specificity.^[2]

On CT imaging, phleboliths present as small, rounded, and hyper-dense foci. A characteristic comet-tail sign, consisting of a central area of calcification with a soft tissue tail representing a pelvic vein, can help diagnose phleboliths with moderate sensitivity and high specificity.^[8]

In the pelvis, the most common differential diagnosis to consider for focal calcifications are phleboliths versus ureteroliths. The comet-tail sign is more characteristic of phleboliths, whereas a rim sign is more typical of ureteroliths.^[8] Phleboliths also demonstrate lower Hounsfield unit (HU) values compared with ureteral calculi (160-350 HU).^[2] CT imaging fails to demonstrate a hypodense center of phleboliths that compares to the central lucency seen on X-ray. Therefore, the absence of central lucency on CT cannot reliably differentiate ureteroliths from phleboliths.^[9]

Due to better soft tissue contrast, MRI is not frequently used to diagnose phleboliths, which are calcifications better visualized on X-ray and CT imaging. On MRI, phleboliths appear as hypointense foci across multiple MRI imaging sequences.^[10]

However, the presence of phleboliths is highly suggestive of venous malformations and hemangiomas, and MRI is often the preferred modality for evaluating these associated vascular anomalies.^[11]

Although phleboliths are mostly incidental findings and rarely produce any symptoms, their presence may suggest vascular abnormalities such as hemangiomas or vascular malformations. Up to 25% of phlebolith identified in patients have been associated with venous malformations.^[12]

Phleboliths can also pose a diagnostic challenge, particularly when differentiating them from other focal calcifications. For example, to differentiate phleboliths from sialoliths in the OMF area, "phleboliths are usually multiple and circular radio-opacities with a laminated morphology and a radiopaque or radiolucent center, while sialoliths are commonly uniform radiopaque and there is more often a single sialolith rather than multiple sialoliths."^[13] Differentiating ureteroliths from phleboliths can also be challenging, although imaging features such as the rim sign and comet-tail sign can help distinguish the two with high specificity, respectively.^[14]

Regarding management and treatment, phleboliths themselves typically do not resolve once calcification has occurred and are unlikely to disappear spontaneously or respond to treatments such as sclerotherapy. Therefore, management is usually directed toward the underlying vascular abnormality rather than the phleboliths themselves. When treatment is required, therapeutic options may include sclerotherapy to shrink the vascular lesion or surgical excision when clinically appropriate.^[15]