Pelvic Phlebolith: A Trivial Pursuit for the Urologist?

OBJECTIVE: Pelvic phleboliths are commonly encountered on plain and CT imaging and remain a source of frustration when attempting to differentiate them from ureteral calculi. Given their frequency, surprising little is known about their significance. We review the literature on pelvic phleboliths, specifically in relation to their history, demography, clinical significance, and methods to distinguish them from ureteral calculi.

METHODS: A comprehensive literature search was performed for all articles concerning pelvic phleboliths.

RESULTS: Pelvic phleboliths were first described in 19th century when the presence of calcified intravenous nodules was observed in human dissection. With the discovery of X-ray imaging in 1895, they have caused much diagnostic controversies since. Histologically they are composed of calcified laminated fibrous tissue, with a surface layer continuous with vein endothelium. Prevalence of pelvic phleboliths in adults is reported to be 38.9%-48%. They are more common in adults aged over 40, and appear to equally affect both genders. They may be associated with diverticulitis, vascular abnormalities, and are more commonly seen in individuals from economically developed countries. The soft-tissue "rim"sign (50%-77% sensitivity and 92%-100% specificity) and a geometric shape (100% positive predictive value [PPV]) are radiological signs predictive of ureteral calculi on unenhanced CT scanning. Radiological signs suggestive of phleboliths include the presence of central lucency (8%-60% sensitivity and 100% specificity), rounded shape (91% PPV), and the comet-tail sign (21%-65% sensitivity and 100% specificity). Phleboliths appear to have a significantly lower Hounsfield unit enhancement than ureteral calculi (160-350 HU).

CONCLUSIONS: Pelvic phleboliths are a common radiological finding, especially in the older population, which continue to present diagnostic challenges in those with suspected ureteral calculi. With greater awareness, the uncertainty can be overcome by identifying defining characteristics when interpreting radiological investigations.