Disclosed herein are elongate flexible medical devices which are capable of axial elongation through a mechanism of eversion or toposcopic expansion. In general, this may be accomplished by providing a flexible tubular body having a proximal end and a distal end. Retraction of the distal end in a proximal direction through the tubular body inverts the tubular body upon itself, causing an axial shortening of an overall length of the tubular device. An original length of the tubular device can be restored by coupling a pressurized media to the proximal end of the tubular device. If the distal end of the tubular device is temporarily restricted or closed, the pressurized media causes the distal end of the tubular device to travel distally until a full length of the tubular device has been restored.