Laparoscopic Radiofrequency Ablation Technique

The laparoscopic approach to radiofrequency ablation of a small renal mass is indicated for anterior, medial, and some lateral renal tumors where the ureter, colon, or small bowel are within 1 cm of the tumor and risk injury.

In addition, the path for percutaneous radiofrequency needle placement for a posterior renal tumor is occasionally impeded by a large spleen, liver lobe, or lung parenchyma. In these cases, if radiofrequency ablation is intended, a laparoscopic approach is indicated.

The patient is positioned in a modified flank position, and three or four transperi-toneal laparoscopic trocars are placed as with laparoscopic nephretomy. The kidney is then mobilized within Gerota's fascia, and the tumor is identified and evaluated with laparoscopic ultrasound. The tumor is exposed and the overlying fat is excised and sent for pathologic analysis.

We use the radiofrequency interstitial tumor ablation Model 1500X electrosurgical generator and 15-gauge Starburst XL probea that is a dry-probe, temperature-based

General indications for radiofrequency ablation of renal tumors are the same as with conventional nephron-sparing surgery surgery and include the following: contrast-enhancing (>\10-12 Hounsfield units), small renal masses (<4 cm), tumor in solitary kidney, bilateral tumors, and renal insufficiency.

The laparoscopic approach to radiofrequency ablation of a small renal mass is indicated for anterior, medial, and some lateral renal tumors where the ureter, colon, or small bowel are within 1 cm of the tumor and risk injury.

aRITA Medical Systems, Inc., Mountain View, CA.

An advantage of the temperature-based system is that during the cool down period, passive tissue temperatures are monitored in real time. If the treated tissue maintains a temperature above 65°C to 70°C,the surgeon should be confident that cell death has occurred.

system. This radiofrequency system is Food and Drug Administration-approved for the ablation of all soft tissue tumors. The probe consists of nine active tines, five of which also contain a thermistor. The probe is introduced percutaneously at a location that permits near-perpendicular insertion into the renal tumor (Fig. 1). The tines are deployed to a diameter that ablates a zone 0.5 to 1.0 cm greater than the tumor diameter measured on computed tomography and intraoperative ultrasound, in order to ensure complete coagulation of both the tumor and a margin of normal kidney parenchyma. The Starburst XL design is particularly well suited for kidney tumor ablation. The tines deploy in a forward direction from the needle tip so that when the probe is placed perpendicular to the tumor surface, the surgeon can be confident that the greatest energy is deposited at the deep tumor margin—the region of highest blood flow and most likely site of incomplete ablation.

Energy is maintained at less than 150 W until the average temperature of the tines reached a target temperature of 105°C (per the manufacturer's recommendation). Once the target temperature is reached, it is maintained for three to eight minutes, depending on the size of the tumor (Table 1). At no time during treatment is the impedance allowed to exceed 80 ohms. The lesion created by the radiofrequency probe is a direct function of its deployed diameter and the minimum time activated (Table 1). As such, real-time ultrasound monitoring of the ablation is not necessary because activating the probe for longer periods of time does not change the lesion size. After a 30-second cool down period, a second cycle is performed using the same settings, tine deployment, and time. If the tumor is not spherical or larger than 4 cm, the probe is repositioned and tines redeployed.

An advantage of the temperature-based system is that during the cool down period, passive tissue temperatures are monitored in real time. If the treated tissue maintains a temperature above 65°C to 70°C, the surgeon should be confident that cell death has occurred.

Following treatment, the tract is ablated as the probe is withdrawn to prevent bleeding and to minimize the risk of tumor seeding. Track ablation is stopped once the probe is withdrawn from the kidney.

Based on our laboratory experience, the renal hilum should not be occluded during laparoscopic ablation (23). Although it likely increases the ablation diameter and shortens the time to reach the target temperature by eliminating the circulatory heat sink, there is a risk of intravascular thrombus propagation and unpredictable normal parenchyma damage.

Depending on tumor size and location, the ablated tumor can be left either in situ or excised. Tumors that are endophytic or located in the mid-pole are left in situ with our protocol. In these cases, diagnostic biopsies are taken after ablation using a laparo-scopic 5-mm toothed biopsy forceps (Fig. 1). Biopsies are not taken before ablation to minimize the risk of bleeding and tumor seeding (25). Tumors that are exophytic or in a favorable polar location can be completely excised in a hemostatic fashion without hilar

FIGURE 1 ■ (A) The tines are deployed beside the tumor to check appropriate ablation diameter. (B) The probe is inserted perpendicular to the tumor. Tines are deployed and confirmed with a laparoscopic ultrasound. (C) The ablation is underway. (D) The ablated renal tumor after a biopsy.

FIGURE 1 ■ (A) The tines are deployed beside the tumor to check appropriate ablation diameter. (B) The probe is inserted perpendicular to the tumor. Tines are deployed and confirmed with a laparoscopic ultrasound. (C) The ablation is underway. (D) The ablated renal tumor after a biopsy.

TABLE 1 ■ Renal Tumor Radio Frequency Ablation Settings TABLE2 ■ Summary of Laparoscopic RFA

Target

Time at

Tumor size

temperature

target temperature

No. of

(cm)

(°C)

(min)

cycles

<1.0

105

3

1(2)

1.0-2.0

105

5

2

2.0-3.0

105

7

2

3.0-4.0

105

8

2

Port placement as per standard laparoscopic nephrectomy or partial with 12-mm port in lower abdomen to accommodate laparoscopic US probe Use laparoscopic US to localize tumor Start dissecting Gerota's off of tumor, beginning at medial edge Completely expose tumor surface Hilar dissection, mobilization of kidney is unnecessary Posterior located tumor can be approached via retroperitoneoscopy RFA probes should be used according to manufacturer's instructions RITA XL probes are inserted perpendicular into the tumor Tines are deployed to diameter 0.5 cm beyond tumor diameter as measured on preoperative CT

Laparoscopic US is used to confirm deployment of tines Ablate according to tumor size (Table 1)

Abbreviations: RFA, radiofrequency ablation; CT, computed tomography; US, ultrasound.

occlusion (26). The specimen is placed in a laparoscopic bag and extracted through one of the trocar sites at the conclusion of the case. Adjunctive hemostatic measures, such as argon beam coagulation, fibrin glue, and/or oxidized cellulose can be applied in these cases to prevent delayed bleeding (Table 2).

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