Endometrial ablation: a look at the newest global procedures

Many patients who undergo endometrial ablation via either standard or global techniques can tolerate the procedure well with local anesthesia and intravenous sedation. This is especially true for global procedures because they are of short duration, i.e., about 5 to 20 minutes, depending on the method. Much of the pain results from cervical dilation and manipulation, as well as trauma to the endometrium. Therefore, the global ablation techniques that utilize the smallest probe (5.5 mm or smaller) and freeze the uterus, i.e., cryoablation, require the least anesthesia.

After the patient has been properly selected and prepared, proceed with one the global techniques—cryoablation, bipolar desiccation, or hydrothermal ablation—outlined in this article.

Cryoablation

Technique. Dilate the cervix and insert a 5.5-mm cryoprobe into the uterine cavity. Cool the probe to less than-80 degrees Celsius by liquid differential gas exchange, described by Joule-Thompson, utilizing the cooling unit (Her Option; CryoGen, San Diego, Calif). An elliptical ice ball approximately 3.5 by 5 cm will then form around the probe.

Using abdominal ultrasound guidance, follow the edge of the ice ball into the uterine muscle at 1 cornu. (While the edge of the ice ball reaches 0 degrees Celsius, which is nondestructive to surrounding tissue, 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 of the uterus, stop the procedure (Figure 1). Heat the probe to body temperature and remove it from the cornu. Repeat the process in the contralateral cornu (Figure 2) and, in large uteri (greater than 10 cm sound), in the lower uterine segment (Figure 3). Each freeze cycle takes about 5 to 6 minutes.

FIGURE 1

Using ultrasound guidance, follow the edge of the ice ball into the uterine muscle at 1 cornu. Stop before the edge of the ice ball approaches the serosa.

FIGURE 2

Heat the probe to body temperature, remove it from the first cornu, and repeat the process in the contralateral cornu.

FIGURE 3

For large uteri (greater than 10 cm sound), perform another freeze cycle in the lower uterine segment. Each cycle takes about 5 to 6 minutes.The number of ice balls needed to destroy the entire uterine cavity and the length of time required to perform the procedure depend on the size of the cavity. In general, 2 to 3 ice balls are sufficient, and the entire procedure takes 10 to 20 minutes.

In a recent randomized multicenter study, researchers investigated whether a freeze cycle longer than recommended would result in better outcomes. At 12-month follow-up, 7 (64%) of the 12 patients who underwent treatments of 5 to 7 minutes rather than 4 minutes were amenorrheic/spotting, with a 91% success rate.⁷ Larger studies are underway to confirm these data. Further, repeat treatment can contribute to better outcomes, especially when the patient receives leuprolide acetate prior to the procedure.⁸

Advantages. 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. Further, while the hysteroscope used in standard ablation allows the physician to see only the destruction of the surface epithelium, ultrasound enables the surgeon to visualize the depth of treatment during cryoablation.

Another advantage: Freezing tissue causes less pain (cryoanesthesia) than the heat energy associated with other ablation devices.

Disadvantages. While ultrasound visualization has its benefits, it also can complicate matters because accurate imaging and interpretation require a certain level of skill. For Ob/Gyns not experienced in ultrasound, there is a potential for poor positioning of the probe, which could lead to bowel and bladder injuries. Further, physicians can mistakenly place the cryoprobe back into the treated cornu instead of the contralateral side, leading to ablation of the uterine serosa. Lastly, the technology involved in this procedure increases the cost of the equipment and disposable instruments.

What the evidence shows. According to an unpublished study conducted by Cryogen, 54% of 222 patients experienced amenorrhea or staining only at 6-month follow-up. Ninety-three percent of the patients had a Patient Bleeding Assessment Card (PBAC) score of less than 75, and 75% of the patients had a greater than 90% reduction in their PBAC scores. (A score of greater than 150 was needed to enter the study; the score is reached by assigning a value to the amount of staining on a validated pad and adding these points based on the number of pads used per cycle.)