Recanalization of Inferior Vena Cava and Bilateral Iliac Veins 15 Years after May-Thurner Syndrome-Related Occlusion.

May-Thurner syndrome (MTS) is a relatively rare condition involving mechanical compression of a vein between an artery and a bone which may result in venous stenosis, reflux, occlusion, or deep vein thrombosis (DVT). The most common location for MTS to occur is the left iliocaval confluence, specifically where the left common iliac vein crosses under the right common iliac artery and becomes compressed against a vertebral body. Our case represents a unique presentation of MTS where a missed diagnosis of MTS during a presentation of acute LLE DVT over 15 years ago which would later progress to chronic bilateral iliac vein occlusion and IVC obliteration. This also ultimately contributed to recurrent left lower extremity (LLE) DVT. The hypothesis for this case is that our patient had May-Thurner syndrome at the time of his original LLE DVT 15 years ago that went undiagnosed. He likely had "spillover" thrombus that occluded the right iliac venous system and resulted in IVC thrombosis at that time. What resulted was obliteration of the IVC between the iliac vein confluence and the renal vein level and bilateral iliac veins. The chronicity of the occlusion creates a uniqueness to this case as there are sparse reports of such longstanding ileo-caval occlusion being recanalized after such a prolonged duration.