Venous Malformations: Phleboliths Correlate With the Presence of Arteriovenous Microshunts

OBJECTIVE. The objective of this study was to identify differences between venous malformations (VMs) with arteriovenous (AV) microshunts and VMs without AV microshunts. MATERIALS AND METHODS. In this retrospective study, 83 patients with untreated VMs of the extremities underwent a prospectively defined MRI protocol performed at 3 T MR images were reviewed to determine localization and extent of each VM and tissue involvement. The VM volume and the lesion volume relative to body surface were measured. The number of phleboliths within the lesions was determined. Using time-resolved MR angiography, the hemodynamic subtype (VM with AV microshunts versus VM without AV microshunts) was classified, and the interval between the onset of arterial enhancement and lesion enhancement (t(onset)) was measured. Clinical data were reviewed to determine patient demographic characteristics, the onset of symptoms, the frequency of thrombophlebitis, and the pain score. RESULTS. Of the 83 patients, 56 (67%) presented with AV microshunts. The t(onset) (p <= 0.001), absolute and relative lesion volume (p = 0.001), and number of phleboliths (p = 0.038) differed significantly between these two subgroups. With use of a multivariable regression model, the strongest indicator for VM with AV microshunts was the presence of more than two phleboliths (odds ratio, 2.80; p = 0.007). No differences were noted regarding patient demographic characteristics and history or lesion morphologic features or anatomy. CONCLUSION. Occurrence of AV microshunts in untreated VM is a frequent phenomenon. This hemodynamic subtype is significantly associated with phleboliths and large lesions. The subtypes did not differ in terms of history and clinical course