Method and apparatus are disclosed for thermally destroying a layer of an organ such as the mucosal layer of the gallbladder. The apparatus includes a catheter having an elongated member having a plurality of lumens therein. At the distal end of the elongated member is an electrode for emitting radiofrequency current to the mucosal layer. Also at the distal end is a capacitive balloon electrode surrounding the current-emitting electrode for containing an electrolyte solution and for distributing the radiofrequency current to the mucosal layer. The balloon electrode is expanded with the electrolyte solution to conform and make contact with the mucosal layer. The electrolyte solution has a resistivity significantly less than the resistivity of the gallbladder wall, as well as the gallbladder bile, to cause a concentrated power deposition in the mucosal layer. The distal end of the catheter is endoscopically inserted into the body of the gallbladder by a retrograde route through the duodenum, common bile duct and cystic duct. While the balloon electrode is being expanded, the bile present in the gallbladder is drained through one of the lumens in the elongated member. The apparatus also includes a radiofrequency generator for supplying radiofrequency current to the current-emitting electrode. The current-emitting electrode is energized for a period of time to cause the mucosal layer to be heated for a predetermined period of time to thermally coagulate the mucosal layer of the gallbladder and cystic duct. A dispersive electrode is positioned on the skin of the patient's body to facilitate a complete circuit back to the generator without causing trauma to the patient.