A tamponade trocar includes an elongate balloon having a closed distal end and is adapted to expand from a small diameter to a large diameter. A cannula is positioned at a proximal portion within the balloon lumen. A rigid stylet is removably positioned within the balloon and cannula lumens. A distal end of the stylet supported balloon is inserted into a perforation in a body wall and advanced into a body cavity while the balloon is unexpanded. The balloon is expanded and the cannula is advanced to a distal portion of the balloon lumen and across the body wall. At this stage, the perforation is dilated and in compressive tamponade. The proximal portion of the balloon may be removed and a seal housing may be coupled to the proximal end of the cannula. The distal end of the balloon may be punctured and opened, making the trocar ready for use.