A system (1) and a device (3) is used in a fundoplication procedure in order to avoid over-tightening of the fundus of the stomach when the fundus is being wrapped around the esophagus (7) adjacent the lower oesophageal sphincter (5). The device (3) comprises a catheter (8) having a primary balloon (12) located at a distal end (9) thereof which is inflatable with a saline solution by a primary pump (26). A pair of spaced apart primary stimulating electrodes (32) on the catheter (8) within the primary balloon (12) receive a stimulating current signal from a constant current signal generator (40) under the control of a microprocessor (43), which reads voltage signals from spaced apart primary receiving electrodes (35) on the catheter (8) in the balloon (12). The microprocessor (43) determines the diameter of the primary balloon (12) at locations adjacent the primary receiving electrodes (35), and an image (47) of the inflated primary balloon (12) is displayed on a visual display screen (48) along with corresponding diameter values of the primary balloon (12). The primary balloon (12) is located in the sphincter (5) and inflated with the saline solution until the sphincter (5) has been dilated to a desired diameter, which is observed on the visual display screen (45). As the fundus of the stomach is being wrapped around the esophagus (7) adjacent the sphincter (5) the diameter of the primary balloon (12) is observed so that the fundus is not over-tightened. A secondary balloon (50) on the catheter (8) is independently inflatable for simulating a bolus of food in the esophagus (7) so that the dilating response of the sphincter (5) can be determined by observing the image (47) of the primary balloon (12) and the diameter values thereof on the visual display screen (45).
