Principles of cryosurgery.

The mechanism by which a cryogen destroys cells is complex. The formation of a hemispherical iceball composed of thermogradients, each of which maintains a temperature proportional to its distance from the application point, initiates the cryoinjury. The cardinal rule of cryosurgery includes a rapid freeze, which produces highly damaging intracellular ice formation and closely-packed thermogradients, coupled with a slow thaw. Multiple freeze/thaw cycles are most destructive, producing ischemic necrosis. Histological and clinical aspects are discussed, as well as complications and follow-up procedures.