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the increase in incidentally found small renal tumors has served as an impetus to develop less invasive parenchymal - sparing techniques for tumor resection .
recent studies have shown that renal parenchymal - sparing procedures yield comparable outcomes with regard to tumor control compared with outcomes of radical nephrectomy for small tumors . to reduce the morbidity of partial nephrectomy ,
several investigators have reported laparoscopic partial nephrectomy ( lpn ) in select patients with small lesions .
several hemostatic modalities have been used during lpn with variable success , including argon beam coagulation , neodymium : yag laser , harmonic scalpel , hand assistance , bipolar electrical current , unipolar spray electrical current , ultrasound scissors , microwave tissue coagulation , cable - ties , and radiofrequency ablation .
based on the success of holmium : yag laser prostatectomy , we designed a study to evaluate the feasibility and efficacy of the holmium laser in performing lpn in a porcine model .
in an animal care and use committee - approved study , laparoscopic transperitoneal lower pole partial nephrectomy was performed using the holmium : yag laser in 5 female farm pigs ( average weight , 45 to 50 kg ) . a pilot study in a single animal
four separate lpn were performed using the holmium laser at settings of 0.5 joules at 55 pulses / sec , 0.8 joules at 40 pulses / second , or 0.2 joules at 60 pulses / second .
all settings resulted in successful partial nephrectomy with good hemostasis ( estimated blood loss , < 50 cc ) .
the setting of 0.2 joules at 60 pulses / second provided an almost continuous delivery of energy , which produced smooth cutting of the kidney and was therefore chosen for the current study .
the holmium laser was used in all 5 animals to perform laparoscopic transection of the lower pole of the left kidney ; 2 weeks after the procedure , a right lower pole laparoscopic partial nephrectomy was performed , and the animals were immediately sacrificed . for the purposes of analysis , the initial left lpn kidneys are referred to as the survival kidneys , and the right lpn kidneys are the acute kidneys .
general endotracheal anesthesia was induced using an initial dose of terazol 4 mg / kg and ketamine 2.2 mg / kg with isoflurane 2% used for maintenance .
three ports were placed : a 12-mm trocar just lateral to the rectus muscle at the level of the umbilicus , a 12-mm trocar in the lower lateral quadrant at the midclavicular line , and a 12-mm trocar approximately halfway between the umbilicus and the xiphoid at the midclavicular line . the lower pole of the kidney was mobilized , and the proximal ureter was displaced medially , away from the lower pole of the kidney .
a 2-mm port was then inserted under laparoscopic guidance at the level of the lower pole of the kidney to accommodate and stabilize the end - fire holmium : yag laser fiber ( trimedyne corporation , irvine , ca ) ( 1000 m [ n=6 ] or 550 m [ n=4 ] ) . with the laser set at 0.2 joules / pulse and 60 pulses per second ,
an incision was initiated 1 cm below the level of the hilum with direct laser contact on the parenchyma .
then a groove was cut into the cortex of the kidney from medial to lateral ( figure 1 ) , which was deepened until the lower pole was completely excised .
the laser was defocused as necessary to coagulate small areas of bleeding . by withdrawing the laser from contact with the cut surface , a larger surface area
was encompassed by laser energy ( defocused ) , permitting coagulation of any bleeding surface .
fibrin glue ( 1 cc ) was then applied to the cut edge of the kidney to seal the collecting system . in the animals undergoing
left lpn ( survival kidney ) , the specimen was removed intact using an organ entrapment sack via an extension of a trocar site .
serum creatinine was obtained on postoperative days 0 , 1 , 4 , and 7 . at 14 days , the pigs were anesthetized and a laparoscopic right lower pole partial nephrectomy was performed .
the kidneys were then harvested and an in situ left retrograde pyelogram was performed ( n=4 ) .
general endotracheal anesthesia was induced using an initial dose of terazol 4 mg / kg and ketamine 2.2 mg / kg with isoflurane 2% used for maintenance .
three ports were placed : a 12-mm trocar just lateral to the rectus muscle at the level of the umbilicus , a 12-mm trocar in the lower lateral quadrant at the midclavicular line , and a 12-mm trocar approximately halfway between the umbilicus and the xiphoid at the midclavicular line . the lower pole of the kidney was mobilized , and the proximal ureter was displaced medially , away from the lower pole of the kidney .
a 2-mm port was then inserted under laparoscopic guidance at the level of the lower pole of the kidney to accommodate and stabilize the end - fire holmium : yag laser fiber ( trimedyne corporation , irvine , ca ) ( 1000 m [ n=6 ] or 550 m [ n=4 ] ) . with the laser set at 0.2 joules / pulse and 60 pulses per second ,
an incision was initiated 1 cm below the level of the hilum with direct laser contact on the parenchyma .
then a groove was cut into the cortex of the kidney from medial to lateral ( figure 1 ) , which was deepened until the lower pole was completely excised .
the laser was defocused as necessary to coagulate small areas of bleeding . by withdrawing the laser from contact with the cut surface , a larger surface area
was encompassed by laser energy ( defocused ) , permitting coagulation of any bleeding surface .
fibrin glue ( 1 cc ) was then applied to the cut edge of the kidney to seal the collecting system . in the animals undergoing left lpn ( survival kidney ) ,
the specimen was removed intact using an organ entrapment sack via an extension of a trocar site .
serum creatinine was obtained on postoperative days 0 , 1 , 4 , and 7 . at 14 days
, the pigs were anesthetized and a laparoscopic right lower pole partial nephrectomy was performed .
the kidneys were then harvested and an in situ left retrograde pyelogram was performed ( n=4 ) . gross inspection and histopathologic evaluation using hematoxylin and eosin staining were performed .
all lower pole partial nephrectomies were successfully completed , and hemostasis was adequate in all cases .
no statistically significant differences were noted in specimen length ( as a percentage of renal length ) or weight between the acute and survival groups .
the differences in the operative time can be accounted for by the additional time required to apply fibrin glue , remove the specimen , and close the trocar sites in the survival animals .
no difference in the cutting or hemostatic ability existed between the 550 and 1000 m fibers .
left retrograde pyelograms performed on 4 survival animals demonstrated extravasated contrast in 2 animals that was contained by small bowel that adhesed to the cut surface of the kidney .
the acute amputation sites had a slightly irregular surface contour with minimal amounts of adhesed blood and fibrin .
figure 2 shows a representative cut surface of the kidney after an acute and 2-week survival lpn .
microscopic sections from the acute amputation sites showed mild histologic changes including increased cytoplasmic eosinophilia of the renal tubules with blurring of the cytoplasmic borders and elongation of the nuclei .
sections from the 2-week specimens showed a 1.5- to 2.0-mm zone of organized fibrosis with admixed lymphohistiocytic inflammation .
with the increase in incidentally detected renal lesions , the indications for partial nephrectomy are expanding .
however , the procedure is more technically challenging than radical nephrectomy , both with the open and laparoscopic approaches . in contradistinction to open partial nephrectomy where hilar occlusion limits blood loss , the laparoscopic approach precludes safe hilar occlusion due to the risk of warm renal ischemia .
furthermore , routine suturing of transected vessels during lpn is technically challenging and time - consuming .
these concerns have prompted a search for techniques that provide safe , reliable hemostasis during lpn .
winfield and colleagues performed the first lpn in 1992 in a patient with a lower - pole stone - bearing caliceal diverticulum .
an electrosurgical blade and laparoscopic argon beam coagulator were used to achieve hemostasis , which was further facilitated by closure of gerota 's fascia .
winfield and associates subsequently reported on lpn in 6 patients , among whom 2 required open conversion .
the argon beam coagulator was also used to achieve hemostasis in this group of patients .
janetschek and colleagues used a neodymium : yag laser ( n=1 ) , argon beam coagulator ( n=1 ) , and bipolar coagulation forceps ( n=5 ) along with oxidized cellulose and gelatin resorcinol formaldehyde glue to perform 7 laparoscopic wedge resections for small solid masses ( 1 cm to 2 cm ) without significant complications .
hoznek and coworkers performed retroperitoneal lpn in 13 patients using rotating tip coagulating scissors , bipolar coagulator , harmonic scalpel , and occasional hilar occlusion to incise the kidney and collagen mesh with gelatin resorcinol formaldehyde glue to achieve hemostasis .
recently , yoshimura and coworkers utilized a microwave tissue coagulator to perform laparoscopic partial nephrectomy in 6 patients with small renal tumors ( < 25-mm ) . also , wolf et al performed 10 lpn using hand assistance in 8 with comparable convalescence to open partial nephrectomy . in these lpn
as can be discerned from the various methods used to achieve hemostasis in these series , an ideal surgical technique has not yet been developed . since 1994
, the availability of high - powered laser systems has expanded the applications of laser technology from stone fragmentation to tissue ablation and incision .
the holmium : yag laser has a wavelength that is strongly absorbed by water ( 2100 nm ) and has a 0.5-mm depth of penetration . the ability to cut and ablate with the holmium laser is the result of rapid heating of water in tissue .
johnson and colleagues found that the area of coagulative necrosis produced with the holmium laser was less than that associated with the neodymium : yag laser , although both lasers achieved a similar degree of hemostasis in renal tissue . in a porcine model , the holmium laser effectively transected renal parenchyma while maintaining hemostasis without the need for hilar dissection or vascular occlusion .
both the 1000-m and 550-m laser fibers resulted in successful lpn , but the 1000-m fiber was easier to use due to greater stiffness that increased manual precision .
first , the 2-mm port was occasionally vented to facilitate removal of smoke that accumulated during laser activation .
second , when the laser was defocused to coagulate bleeding sites , visibility was occasionally obscured by blood spray , requiring that the camera be maintained at a distance to avoid the spray .
this is a drawback of using the laser in a  dry  co2 pneumoperitoneum as opposed to submersed in saline as is the case with  wet 
lastly , minimizing traction on the cut surfaces of the kidney reduced mechanical trauma to the kidney and subsequent blood loss . instead
in addition , the loss of renal function resulting from a unilateral partial nephrectomy is not adequately quantified by serial serum creatinine measurements and would be better assessed with differential renal function from a renogram . although the holmium laser provided adequate hemostasis , sealing of the collecting system was inconsistent , ( 2 of 4 animals had extravasation on retrograde pyelogram ) .
the reliability of fibrin glue and other products to consistently seal the peripheral collecting system requires further investigation . of note , none of the pigs developed clinical symptoms from these minor leaks .
in clinical use , a perinephric drain would be placed and perinephric fat would be positioned over the cut surface .
finally , a size differential exists between the pig kidney and the adult human kidney .
the holmium laser at lower power settings may not adequately coagulate larger vessels in human kidneys .
our pilot study animal showed that hemostasis was easily attained with higher energy levels ( 0.5 and 0.8 joules ) , and these settings may prove more appropriate for human use .
in fact , we have successfully performed this technique clinically in 3 patients and found the setting of 0.8 joules was able to achieve adequate hemostasis in adult kidneys ( in submission ) .
further clinical evaluation will be necessary to determine this technique 's utility for performing lpn .
the holmium : yag laser is an effective modality for achieving partial nephrectomy in a porcine model . the procedure is quick , safe , and relatively simple . with further study , this technique may be added to the armamentarium of the laparoscopic renal surgeon .
objective : to evaluate the utility of the holmium laser for partial nephrectomy in a porcine model.methods:transperitoneal lower pole laparoscopic partial nephrectomy was performed in 5 farm pigs . 
 all animals underwent a left - sided laparoscopic partial nephrectomy and were kept alive for 2 weeks ( survival group ) . 
 subsequently , a right laparoscopic partial nephrectomy was performed ( acute group ) , and the animals were sacrificed . a 1000-m ( n=6 ) or 550-m ( n=4 ) end - fire holmium laser fiber set at 0.2 joules and 60 pulses per second was used to transect the lower pole of the kidney 1 cm below the level of the hilum . 
 the cut parenchymal surface was then sealed with fibrin glue in the survival animals . 
 the operated on kidneys were inspected grossly and evaluated microscopically.results:laser transection was successfully completed in all cases , and hemostasis proved adequate without any adjunctive measures . 
 no perioperative complications occurred . 
 estimated blood loss was less than 50 cc for each laparoscopic partial nephrectomy . 
 the acute and survival pigs showed no statistically significant differences in specimen size or weight . 
 serum creatinine levels were normal in all survival animals . 
 extravasation was noted on retrograde pyelograms of 2 animals in the survival group.conclusions:the holmium : yag laser provides an efficacious modality for transecting the kidney in a porcine model . 
 clinical trials are necessary to determine its role in laparoscopic partial nephrectomy in humans .