An apparatus for delivering electrical energy includes a cannula and one or more needles extendable from and retractable into a lumen of the cannula. A distal portion of each needle is extendable from the lumen and terminates in a tissue-piercing distal tip. Each distal portion is formed from an electrically conductive and porous material, thereby providing a porous electrode through which electrolytic fluid may flow for delivering electrical energy to tissue surrounding the distal portion. The cannula is introduced into a tissue structure of a patient, the one or more needles are advanced from the cannula, saline is introduced from the porous material to surrounding tissue, and electrical energy from an RF generator is delivered to ablate tissue within the tissue structure.