Instruments for thermally-mediated treatment of a patient's lower esophageal sphincter (LES) to induce an injury healing response to thereby populate the extracellular compartment of walls of the LES with collagen matrices to altere the biomechanics of the LES to provide an increased intra-esophageal pressure for preventing acid reflux. A preferred embodiment is a bougie-type device for trans-esophageal introduction that carries conductive electrodes for delivering Rf energy to walls of the LES (i) to induce the injury healing response or (ii) to "model" collagenous tissues of the LES by shrinking collagen fibers therein.