A medical device comprises a catheter having a wall with an inner surface defining a central longitudinal lumen and an outer surface； and a plurality of separate lumens positioned within the wall between the inner surface and the outer surface, the plurality of separate lumens oriented radially with respect to each other and extending parallel to and offset from the central longitudinal lumen； wherein the plurality of separate lumens have in use a first configuration in which the lumens are substantially filled with liquid such that the catheter has reduced echogenicity when positioned in a body conduit and a second configuration in which the lumens are substantially filled with gas such that the catheter has enhanced echogenicity when positioned in a body conduit.
