Septums are seen as thin vertical bands extending up and down the vein. They may be thin or have areas of patchy echogenicity similar to the leaflets of valves. They may be compared to elongated valve leaflets. One can sometimes follow these bands to their attachment to the wall proximally or distally, forming a sort of "windsock". Some septum form a blind ending sack dividing the vein into two separate chambers, only one of which is in continuity with the cephalad lumen, analogous to a dissection. The "false" lumen may bulge and compress the "true" lumen on Valsalva maneuver. Septum may also show thickening and increased echogenicity, similar to abnormal valves. Differentiation relies upon the absence of an opposing valve leaflet. The septum appears to be taut against the IVUS probe.
