Cryotherapy, or freezing, is done by placing a probe against the cervix which cools the cervix to sub-zero temperatures. The cells damaged by freezing are shed over the next month in a heavy watery discharge. The main advantages of freezing are that it is simple to do and uses inexpensive equipment. One problem with freezing is that the depth cannot be precisely controlled, so some abnormal cells may be left behind. This is less of a problem with small areas of mild to moderate dysplasia, and more of a problem with severe dysplasia and carcinoma-in-situ.
Another problem with cryotherapy is that the cervix often heals inside the canal of the cervix, making future evaluations, difficult. In spite of these problems, most authorities agree that freezing is an acceptable treatment for small areas of mild or moderate dysplasia. Cryotherapy has a high failure rate for treating large areas of dysplasia, and dysplasia that extends into the cervical canal, so other methods are preferable when they are available.