Laparoscopic interstitial laser coagulation of renal tissue with and without hilar occlusion in the porcine model.

PURPOSE

To evaluate the safety and efficacy of interstitial laser coagulation (ILC), applied via a laparoscopic approach, with and without hilar occlusion in the porcine model.

MATERIALS AND METHODS

In nine female farm pigs, bilateral renal mobilization was performed via a transperitoneal laparoscopic approach. Using a 600- micro m bare-tip silicon diode laser fiber inserted 0.5 cm into the lower pole of each kidney, diode laser energy (wavelength 805 nm) was applied for 15 minutes at 6 W. In each pig, the left renal hilum was clamped during ILC. Animals were sacrificed immediately (N = 3) or at 2 weeks (N = 3) or 4 weeks (N = 3). The kidneys were inspected grossly, and the lesions were evaluated microscopically. Nicotinamide adenine dinucleotide (NADH) histochemical staining was performed to assess viability.

RESULTS

Grossly, parenchymal lesions appeared firm and white with a central zone of carbonization, cavitation, or both. Histopathology examination revealed cellular inflammation in acute lesions; chronic lesions demonstrated coagulative necrosis with progressive fibrosis. The NADH staining showed residual viable cells within the treatment zone of survival animals but not in acute animals. The mean size of the treatment zone in kidneys with unoccluded blood flow was 2.4 x 2.1 x 2.0 cm, 4.0 x 3.3 x 2.8 cm, and 3.3 x 3.5 x 2.0 cm in the acute, 2-week, and 4-week group, respectively. Hilar occlusion resulted in a slightly, but statistically insignificantly, larger lesion. In the 2-week survival group, one animal had a left subcapsular hematoma on the hilar-occluded side. In another 2-week animal, extension of the ILC zone was noted beyond the kidney into the psoas muscle. In the 4-week survival group, two animals developed gross hematuria; one had a left perinephric urinoma and urine leak noted at necropsy.

CONCLUSIONS

Renal ILC may represent an alternative minimally invasive technique for ablation of renal tumors. However, histologic evidence of viable cells within the treatment zone mandates refinement of the technique in the animal model before further application in humans. Hilar occlusion does not appear to enhance tissue ablation.