An apparatus includes a transmission member having a proximal end portion and a distal end portion. The transmission member is configured to be inserted into a bodily lumen, and is configured to transfer ultrasonic energy from the proximal end portion to the distal end portion. The transmission member defines a lumen along a longitudinal center line of the transmission member. The distal end portion of the transmission member includes a concave engagement surface and a distal end surface. The distal end surface defines a plane that intersects the longitudinal center line of the transmission member at an angle of between about 75 degrees and about 105 degrees. The engagement surface is configured to engage a target tissue within the bodily lumen to limit movement of the target tissue along the longitudinal center line. The engagement surface defines an opening in fluid communication with the lumen.
