Obstruction of Labial Venous Drainage Following Hyaluronic Acid Injection: Two Case Reports and a Review of the Literature.

Vascular adverse events associated with hyaluronic acid (HA) dermal fillers are typically interpreted as being of arterial origin, while venous involvement of the lip remains poorly characterized. The aim of this report is to analyze and update vascular events of venous origin, particularly within the anatomical territory of the lips. We present two cases of young women who developed an acute increase in lip volume with violaceous congestion shortly after perioral HA injection. The clinical presentation was more consistent with obstruction of venous drainage rather than classic arterial ischemia. Both patients received immediate treatment with hyaluronidase on the same day, followed by close clinical monitoring, achieving complete resolution without tissue loss in approximately five days. Recent perioral venous mapping studies have demonstrated variable labial tributaries and well-defined zones of venous accumulation, supporting the presence of an anatomical substrate for this presentation. These cases highlight a distinct post-filler phenotype that should be differentiated from arterial occlusion, angioedema, and hematoma in order to allow timely treatment and prevent progression to irreversible tissue injury.