An elongated flexible medical device is inserted into a patient's body via a natural orifice, and advanced through the natural orifice to a location proximate innervated tissue that influences renal sympathetic nerve activity. The medical device can be advanced into a body organ and to a location within the organ proximate the innervated tissue. The organ may comprise an organ of the gastrointestinal tract or urinary tract. The medical device may be advanced through and beyond an access hole in a wall of the organ, and situated at a location proximate the innervated tissue. One or both of imaging and ablation energy is delivered from a distal end of the medical device to the innervated tissue. Innervated renal tissue can be ablated using various forms of energy, including RF energy, ultrasound energy, optical energy, and thermal energy.