An cryogenic tissue ablation instrument, comprising: an elongated flexible body having a proximal administration port adapted to engage with a source of pressurized fluid refrigerant, and an administration lumen in fluid communication with the proximal administration port and which extends through the elongated body to a distal portion thereof； a dispersion member coupled to or formed outside the distal portion of the elongated body, the dispersion member including an inner lumen in fluid communication with or otherwise comprising a portion of the administration lumen； and an expandable balloon incorporated on the distal portion of the elongated body and having a wall, an interior surface of the wall defining an interior of the balloon, where the dispersion member extends at least partially inside the balloon and having a plurality of dispersion holes of the refrigerant in fluid communication with the respective administration and interior lumen of the balloon, wherein the dispersion holes of the refrigerant are sized and located in the dispersion member such that a pressurized fluid refrigerant provided in the lumen of Administration will enter the interior of the balloon through the dispersion holes in the form of a liquid spray that contacts and provides substantially uniform cooling of the interior wall surface of a balloon treatment region. wherein the dispersion holes comprising a first plurality of circumferentially spaced refrigerant dispersion holes, and a second plurality of circumferentially spaced refrigerant dispersion holes located distally in the dispersion member from the first plurality, wherein the holes of the second plurality are circumferentially displaced with respect to the holes of the first plurality, characterized by the refrigerant dispersion holes formed out of flaps cut in the dispersion member, wherein the most distal margin of each flap remains attached to the dispersion member and the proximal flap end is depressed in the administrati
