Abstract: A method and device for reducing the size of tissues and/or other materials contained within an intracorporeally positioned organ or artificial containment sac. In one embodiment, the device comprises an elongate cutting tool having a rotatable cutting head or impactor positioned on the distal end of the tool and, optionally, having one or more aspiration/infusion lumens extending longitudinally through the elongate shaft of the tool. In a second embodiment, the device may comprise (a) a separate guide/aspiration/infusion cannula initially insertable into the organ or sac and (b) a separate elongate cutting device which is insertable through and extractable from the prepositioned guide/aspiration/infusion cannula. An automatically deployable protective assembly may be positioned at the distal tip of either embodiment of the device so as to form a protective cage around the rotatable cutting head or impactor.