Ablation Techniques
The application of minimally invasive hysteroscopic techniques to surgically manage intractable uterine bleeding has been well documented as an efficacious and cost-effective alternative to hysterectomy.
The indication for the operation is abnormal uterine bleeding in a woman who wishes to preserve her uterus or in whom a hysterectomy would be judged too risky. The contraindications for surgery would include the presence of adenocarcinoma of the endometrium, atypical hyperplasia, nonreverting benign hyperplasia, dysmenorrhea, or concurrent adnexal mass.
The term ablation has specific meaning. Ablation translates into vaporization of tissue, which is typically accomplished by thermal methods. When tissue cells are heated to 100°C, cell water is converted from a liquid to a gaseous state (steam). This change results in physical volume expansion within the intracellular space and a resultant explosive evaporation of the cell and its contents, that is, the cell virtually disappears. The most consistent and rapid vaporization is witnessed when the 100°C temperature is rapidly attained. For the aforementioned reasons, the best ablation procedures employ laser or radiofrequency (RF) electrosurgery techniques (Fig. 109–1A, B).
The laser used most commonly for endometrial ablation is the neodymium yttrium-aluminum-garnet (Nd-YAG) laser. This laser penetrates liquid media, exerts a supplementary coagulating action, is delivered by a 1-mm fiber via the operating channel of a hysteroscopic sheath, and passes through the endometrium to exert its principal action within the superficial myometrium (Fig. 109–2A through C).
The electrosurgical device of choice is the ball electrode, which alternatively may be delivered to the operative site by a hysteroscopic operative sheath or by a specially constructed sheath designed with an “in-and-out” sliding mechanism. The electrode is a monopolar, double-armed ball, cylinder, or cutting loop (Fig. 109–3).
The final common path (i.e., tissue heating) is identical regardless of whether an Nd-YAG laser fiber or a monopolar electrode is used. The most important factor related to the efficiency of the ablation is the power density, that is, the power absorbed by a unit of tissue (W/cm2) or the energy density (J/cm2), or the product of power density and time in seconds (Table 109–1). For example, the energy density for laser action on tissue over a period of 10 seconds (referring to parameters shown in Table 109–1) would be 8333 × 10, or 83,333 J/cm2.
The technique for ablation utilizing an Nd-YAG laser begins with preparation of the endometrium 1 month before ablation by the administration of gonadotropin-releasing hormone (GnRH) agonist (Lupron). The endometrium has been preoperatively sampled and has shown to be benign (Fig. 109–4A, B). The patient is placed in the dorsal lithotomy position, prepared, and draped. The cervix is dilated, and the operative hysteroscope, to which an endoscopic video camera has been attached, is inserted into the uterine cavity via the transcervical route with the medium intake channel wide open. In this instance, normal saline (0.9%) is the medium of choice (Fig. 109–5).
After inspection of the cavity, the 1200-µm laser fiber is inserted through the operating channel and makes light contact with the endometrium (Fig. 109–6A, B). Beginning on the anterior wall, ablation is initiated. The fiber is advanced under direct panoramic view. As the fiber is drawn toward the hysteroscope, power is effected by depressing the foot pedal of the laser. The operator views the field from the video screen (Fig. 109–7). Row upon row of endometrium is ablated as the laser fiber is dragged over it, analogous to mowing a lawn (Fig. 109–8A, B). After the anterior wall has been ablated, the fundus and the cornua are treated via a side-to-side motion. Finally, the posterior and lateral walls are destroyed (Fig. 109–9). The ablation is carried from the top of the uterus (fundus) to the level of the internal cervical os (Fig. 109–10). The cervix is not
