Cryosurgery in Dogs

Cryosurgery refers to the application of intense cold in order to kill living tissue. Indeed, the procedure is slightly misnamed since no surgical cutting is involved, so 'cryotherapy' is more apt. Cryosurgery is used to treat lumps on the surface of the skin or tumors in places where surgical removal would be difficult, such as the mouth.

It is not necessarily the first option for treatment, but reserved for patients for whom the anesthetic risk is considered unreasonable, such as elderly dogs. The actual procedure is temporarily painful, but can be overcome with local anesthetic. Cryosurgery used to be more popular than it is at present, and now first opinion clinics offer it as a treatment option.

If you've ever been out in severe temperatures, you'll appreciate that 'cold' hurts. For small skin lumps, cryosurgery is temporarily uncomfortable, but for larger lumps, sedation and local anesthetic is required in order to keep the patient still enough to freeze the lump. For more delicate cryosurgery, such as on oral tumors or anal furunculosis, then anesthesia is required. 

The vet will assess each case for suitability for cryosurgery. Hair needs to be clipped from around the lesion, but surgical sterility is not necessary. The surgeon is most likely to use liquid nitrogen contained in a special device with a probe attached to the end. The probe is placed against the lesion and a trigger pulled, which super chills the tip of the probe and anything it is in contact with. 

The tip is held in place until a freeze halo a few millimeters wide develops around the lump. Then the trigger is released and the surgeon waits for the tip to thaw to release it from the tissue. 

This freeze-thaw cycle is repeated two to three times.

The success of cryosurgery depends on choosing the correct type of lump to use it on. It is unlikely to be effective for large lumps (above 11 cm) because freezing cannot penetrate right to the base of the lump. However, for skin tags, warts, or small superficial tumors it is a good choice. 

Another plus of cryosurgery is that the frozen lesion eventually dies off and 'shells out', meaning it falls off. This means there are no painful incisions to be cared for or sutures where there is a risk of the dog pulling them out with the associated wound breakdown. However, this does not mean the dog can be allowed to lick the lesion whilst it is the process of dying and dropping off. 

The active freezing phase is painful, as it disrupts cells and damages nerves. However, once the lesion has thawed the nerves are deadened and so the recovery is non-painful. 

It should be appreciated that the lesions often take around 2 weeks to die and drop off. During this time the lump is liable to swell, and can often look infected and sore. This is nothing to worry about, but a natural process in which the body sloughs off dead tissue. 

Occasionally, a single cycle of three freeze-thaws is not sufficient to get rid of a lesion, in which case it might need to be repeated two to three weeks after the original cycle. 

During the recovery period the area must be protected from licking or chewing, but is best left open to the air. Therefore expect the dog to wear an Elizabethan or buster collar. 

The cost of cryosurgery can be a few tens of dollars for a simple wart removed with a disposable single-use cryo unit, up to several hundred dollars. The latter is likely where a clinic is equipped with a special dewar to store liquid nitrogen, protective equipment for staff, and the special handsets used for treatments.

The cost will rise should anesthesia be needed, which will vary depending on the size of the dog and the add-ons such as intravenous fluids. This could range from $90 to $200.

Cryosurgery is a relatively safe procedure which is used in high risk patients, because of its lack of complications. One of the biggest considerations is that the procedure may need to be repeated if it wasn't successful after one cycle.

In addition, the dying tissue can look and smell unpleasant. The owner needs to be aware of this and be able to cope with an unsightly lesion for the two or three weeks it takes to drop off. 

Many of the conditions for which the use of cryosurgery is appropriate do not have a direct cause, therefore, it is impossible to prevent them. For the dog that has had one skin lump removed, it can't be ruled out that he won't grow a new one at a different site in the future. 

Conditions such as anal furunculosis are linked to a particular breed, in this case the German shepherd. In the future screening programs to detect likely carriers of this disease would help to make appropriate selection of breeding stock a possibility, which the aim of improving the health of the breed.