The first use of laser technology for organ surgery in the animal model was over 30 years ago. Since then, there had been significant improvement in laser technology as well as in understanding of the laser's mechanism of action. Laser partial nephrectomy using a variety of lasers has been described (135-141). The initial animal experiments were performed open surgically, most with hilar clamping.

More recently, Ogan et al. (140) at the University of Texas Southwestern investigated lasers for laparoscopic partial nephrectomy in five farm pigs undergoing bilateral laparo-scopic partial nephrectomy using a 980-nm diode laser. Mean operative time was 2.1 hours, including a mean lasing time of 84 minutes. Adjunctive hemostatic clips were required in three cases to control the larger, more centrally located vessels. The use of fibrin glue in all cases prevented the assessment of the sealing effect of the laser on the collecting system. Histological analysis of the chronic specimens revealed a necrotic margin of 3-5 mm at two weeks. Subsequently, the same group of investigators employed clini-caly the 2100 nm wavelength pulsed Ho:YAG laser to perform laparoscopic partial nephrectomy in one adult male with a complex cyst, one pediatric patient with a nonfunc-tioning lower pole duplicated system, and one adult male with a 2.5 cm exophytic renal tumor (141). Estimated blood loss in the two adult patients was <50 and 500 cm3, respectively. Fibrin glue, oxidized cellulose, and argon beam coagulator were used, and hilar clamping was not performed. No complications were reported. Thereafter, these authors tested the feasibility of laser tissue welding for laparoscopic partial nephrectomy in five pigs (142). An in-house solder consisting of 30% human serum albumin was concentrated to 50%. Chromophore indocyanine green was added to allow selective absorption of an 800-nm laser. After hilar clamping, the lower pole of the porcine kidney was resected with cold endoshears. The albumin solder was dripped onto the cut surface of the kidney, and laser soldering performed. Reportedly an albumin mixture covering was created over the treated surface of the vessels as well as the collecting system. Estimated blood loss was 43 cm3, with a warm ischemia time of 11.7 minutes. None of the chronic kidneys had evidence of urinary leak on ex vivo retrograde pyelogram at two weeks. Gross and histologic examination revealed the solder adherent to the parenchymal surface. The acute extension of the cauterized area into the renal parenchyma was 0.5 mm. Data on the extent of cautery on the chronic specimen were not provided.

Moinzadeh (143) investigated the technical feasibility and short-term outcomes of potassium-titanyl-phosphate laser laparoscopic partial nephrectomy without vascular hilar clamping in the survival, robust calf model. Bilateral transperitoneal laser LPNs of the mid/lower pole was performed using the 80 W potassium-titanyl-phosphate laser on six Jersey calves, each weighing 76-94 kg. The left kidney (n = 6) of each calf underwent chronic laparoscopic partial nephrectomy with one-month follow-up, while the right kidney (n = 6) underwent acute laparoscopic partial nephrectomy with immediate euthanasia. Two techniques, ablative vaporization (n = 5), and wedge resection (n = 7), were evaluated. Renal parenchymal resection and hemostasis were achieved solely with the laser, without any adjunctive hemostatic sutures or bioadhesives. All 12 procedures were successful laparoscopically without open conversion, 11 of which (92%) without hilar clamping. Mean total operative time was 2.9 hours (range, 1.5-5), and blood loss was 119 cm3 (range, 25-300). Mean lasing time was 56 minutes (range, 20-100), with an average energy use of 54 kJ. Any pelvicalyceal entry was efficiently suture repaired laparoscopically with a running vicryl stitch. Mean preoperative and postoperative hemoglobin (10.38 and 10.52 g/dL) and serum creatinine (0.46 and 0.4 mg/dL) were similar. Retrograde pyelography, renal arteriography, and histologic analyses showed no evidence of urinary leak or arteriovenous fistula at one-month follow-up. Shortcomings of such technique included considerable smoke generation during laser laparoscopic partial nephrectomy (no irrigation of the smoke away from the working field possible as during underwater procedures) leading to increased operative time and higher CO2 inflow-rate requirement necessitating two insufflators. However, the authors anticipated smoke evacuation to be less of a problem in the clinical setting, given the smaller peritoneal volume in the human (~3 L) as compared to the calf (~10 L).

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