1. A method for retracting the bowel to provide anterior access to organs lying outside the peritoneum for a surgical instrument, the organs including the spinal column, the aorta and the kidneys, the method comprising steps of: providing an inflatable retractor including a main envelope enclosing a main chamber, the main envelope being in a collapsed state; placing the main envelope of the retractor adjacent the bowel; inflating the main chamber to an expanded state to retract the bowel; piercing an aperture in the main envelope to provide access for the surgical instrument passed into the main chamber to contact the peritoneum overlying the organ to be treated; and maintaining the main chamber in the expanded state notwithstanding the aperture pierced in the main envelope.