Technique. The cervix is dilated. The cryoprobe is inserted into the uterine cavity. The probe is cooled to less than-80 degrees Celsius by liquid differential gas exchange, utilizing the cooling unit (Her Option, CryoGen).
An elliptical ice ball approximately 3.5 by 5 cm will then form around the probe.
The edge of the ice ball is followed into the uterine muscle at 1 cornu using abdominal ultrasound guidance.
The edge of the ice ball reaches 0 degrees Celsius ( nondestructive to surrounding tissue ) but the endometrium is permanently destroyed approximately 1.5 cm from the edge of the ice ball, where a temperature of-20 degrees Celsius is reached.)
Before the outer edge of the ice ball approaches the serosa (outer layer)of the uterus, the procedure is stopped.
The probe is heated to body temperature and removed from the cornu. The process is repeated in the contralateral cornu.
In a large uterus ( cavity greater than 10 cm ), a further freeze cycle is performed in the lower uterine segment.
Each freeze cycle takes about 5 to 6 minutes.
In general, 2 to 3 ice balls are sufficient, and the entire procedure takes 10 to 20 minutes.
Repeat treatment can improve outcomes, especially when the patient receives leuprolide acetate prior to the procedure.
The primary advantage of cryoab-lation is that it is not a totally blind procedure. The visual feedback provided by the ultrasound facilitates complete ablation of the entire uterine cavity, regardless of size.
While the hysteroscope used in standard ablation allows the gynaecologist to see only the destruction of the surface epithelium, ultrasound enables the gynaecologist to visualize the depth of treatment during cryoablation.
A further advantage is freezing tissue causes less pain (cryoanesthesia) than the heat energy associated with other ablation devices.
Disadvantages. While ultrasound visualization has its benefits, not all gynaecologists has the required level of skill required. Poor positioning of the probe could lead to bowel and bladder injuries. In addition placing the cryoprobe back into the treated cornu instead of the contralateral side leads to ablation of the uterine serosa.
Lastly, the technology involved in this procedure increases the cost of the equipment and disposable instruments.
Seventy five per cent of the patients had a greater than 90% reduction in their menstrual blood loss.