A catheter device for renal denervation ablation includes a flexible catheter shaft having an electrically insulating expandable member in its distal portion with at least one electrode located proximal to the member, at least one electrode located distal to the member, and with openings in the distal shaft with at least one opening proximal to the proximal electrode and one opening distal to the distal electrode of said electrode pair, said openings connected through an inner lumen in the catheter that provides a path for blood to flow through the expandable member. In one embodiment, the device comprises a flexible catheter shaft with a multiplicity of recessed paired electrodes disposed in recessed spaces in its distal portion, such that an electrically conducting portion of each electrode is exposed to the exterior of the catheter within a recessed space, and with an electrical insulator separating the electrodes of each pair.
