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Preliminary Results of Laser Tissue Welding in Extra Vesical Reimplantation of the Ureters
0022-534 7/94/1512-0514$03.00/0 THE JOURNAL OF UROLOGY Copyright© 1994 by AMERICAN UROLOGICAL ASSOCIATION, INC.
Vol. 151, 514-517, February 1994
Printed in U.S.A.
PRELIMINARY RESULTS OF LASER TISSUE WELDING IN EXTRAVESICAL REIMPLANTATION OF THE URETERS ANDREW J. KIRSCH, GREGORY E. DEAN, MEHMET C. OZ, STEVEN K. LIBUTTI, MICHAEL R. TREAT, ROMAN NOWYGROD AND TERRY W. HENSLE* From the Department of Urology, Squier Urological Clinic and the Department of Surgery, The Columbia University College of Physicians and Surgeons, New York, New York
ABSTRACT
One exciting potential use of laparoscopic technology is the extravesical reimplantation of the ureters. We have assessed the efficacy of laser-activated fibrinogen solder to close vesical muscle flaps over submucosal ureters (Lich-Gregoir technique) in a canine model. Four dogs were subjected to unilateral flap closures via a protein solder (indocyanine green and fibrinogen) applied to the bladder serosa and exposed to 808 nm. continuous wave diode laser energy. Contralateral reimplantation was performed using 4-zero vicryl muscle flap closures (controls). At 7, 14 and 28 days postoperatively, intravenous pyelograms confirmed bilateral ureteral patency. At intravesical pressures above 100 cm. H20, there was no evidence of wound disruption in either group. Nondisrupted wound closures were sectioned and strained until ultimate breakage to determine tensile strength. At each study interval the laser-welded closures withstood greater stress than the controls. Although these data represent single tissue samples and are not amenable to statistical analysis, laser-welded closures appeared to be stronger at each study interval. In conclusion, laser-welded vesical wound closures appear at least as strong as suture closures in the canine model. KEY WORDS:
ureter, replantation, lasers, laparoscopy
Technological advances in urology and in the whole field of minimally invasive surgery have enabled urologists to diagnose and treat a wide variety of abnormalities via the laparoscopic approach. Although this strategy seems advantageous, many drawbacks exist. Intracorporal tissue closures and anastomoses via the laparoscope are technically difficult. While intracorporal suturing is possible, it remains tedious and time consuming. The use of a laparoscopic gastrointestinal stapler may solve this problem in bowel surgery, but in the urinary tract a finer anastomosis is often necessary, and foreign bodies, such as staples, may lead to urolithiasis and infection. Tissue welding may not only overcome this obstacle but may also expand the number of procedures being done endoscopically. One such use of laser soldering is in ureteral reimplantation. We propose reimplanting ureters via the extravesical approach (Lich-Gregoir technique) using low power laser welding technology for tissue closure. Laser-assisted tissue welding in urologic surgery has been used for primary anastomoses of the urethra, 1- 3 vas deferens4- 7 and ureter, 8 with promising results. To date, no published reports have described the use of such technology in ureteral reimplantation and vesical wound closure. We have assessed laser tissue welding to evaluate its utility in detrusor wound closure and its future laparoscopic application. MATERIALS AND METHODS
Fibrinogen preparation (fibrinogen glue). Human fresh frozen plasma was transferred to test tubes and placed in a freezer at -SOC for at least 12 hours. The tubes were then thawed at 4C and centrifuged at 1000 g for 15 minutes. The supernatant was decanted, leaving the precipitate, fibrinogen. The high viscosity of this solution permits easy manipulation with forceps. Fibrinogen can be stored at -SOC for as long as 1 year. 9 Dye preparation. Indocyanine green dye (5 µg.) (Becton Dickenson, Baltimore, Maryland) was mixed with sterile water to Accepted for publication September 14, 1993. * Requests for reprints: Director, Pediatric Urology, The Babies Hospital, Columbia-Presbyterian Medical Center, 3959 Broadway, New York, New York, 10032. 514
saturation. The half-life of this solution is approximately 10 hours. The dye has an absorption peak at 805 nm. and an absorption coefficient of 2 x 106/m.-1 cm.-1 • Indocyanine green (0.2 ml.) was combined with the fibrinogen glue and mixed 30 minutes before each operation. Laser system. Tissue welding was performed with a diode laser module (System 7200, Spectra-Physics, Mountain View, California) coupled to a hand-held focusing optic. The laser system consists of a phased array of gallium-aluminum-arsenide semiconductor diodes. The major wavelength output of the laser diode is 808 ± 1 nm. Additional bands of laser energy occur in the visible red spectrum and allow the operator to visualize the spot size of the laser during the tissue weld. With the addition of a focusing optic, the beam diameter is 2 mm. at a distance of 4 cm. The focusing optic permits a greater working distance, providing greater visibility of the welded area. Laser power was measured at the output of the focusing optic with a laser power meter (Model 201, Coherent Science Division, Palo Alto, California). Operative procedure. Four conditioned male dogs (ages 3 to 4 years, weighing 26 to 31 kg.) were fasted 24 hours before bilateral extravesical reimplantation. The dogs were anesthetized with pentobarbital (35 mg./kg.) and intubated. Before surgery, a cephalosporin was given intravenously and urinary catheters were placed. The bladder was filled to distention, and a lower midline incision was made. The rectus bellies were retracted exposing the underlying bladder. The superficial fascia overlying the bladder was excised. The ureters were exposed and encircled with Penrose drains. The intramural portion of the distal ureter was separated from the detrusor muscle circumferentially, using a clamp, down to the vesical submucosa. Using a #15 blade, the detrusor muscle was divided down to the submucosa, along the course of the ureter, in the cephalad direction for 2 cm. from the ureter (fig. 1, A). Lateral flaps were created in the bladder muscle against the submucosa to cover the ureter. The ureter was then placed into the groove in contact with the bladder mucosa. The muscle flaps were then closed over the ureter by either interrupted 4-zero vicryl sutures or dye-enhanced (ICG) fibrinogen glue with diode laser (808 nm.)
515
LASER TISSUE WELDING IN URETERAL REIMPLANTATWN
of uninterrupted tissue. Suture material was left intact in the sutured closure group. Each section was tested using a tensile grip applicator (Instron Corporation, Canton, Massachusetts, Table Model 1130 Instron). The bladder tissue was strained perpendicular to the axis of the closure until ultimate breakage. Relevant elastic constants, including modulus and tensile break values, were calculated from the strain profile for each tissue section. Histologic analysis. Freshly obtained unstressed tissue was preserved in 10% formaldehyde solution buffered to physiologic pH for histologic staining with hematoxylin and eosin (H & E). RESULTS
Fm. 1. Operative procedure. A, bladder muscle incised to level of mucosa in cephalad direction. B, conventional rnuscularis flap closure. Muscle edges aligned with single suture. Fibrinogen/indocyanine green (ICG) glue applied. C, laser-welded flap closure.
activation (fig. 1, Band C). The amount of glue required ranged from 2.0 to 3.0 ml. A single stay suture of 4-zero catgut was used to align the muscle flaps in the laser group. The laser was operated on continuous mode output at a power of 300 mW, resulting in a power density of 9.6 W /cm. 2 • Laser energy was applied over the length of the incision until desiccation of the fibrinogen was observed as a green to white color change. The celiotomy incision was then closed in layers. Measurement of renal function and ureteral patency. At 7, 14 and 28 days intravenous pyelograms (IVP) were obtained at 1, 15 and 30 minutes after intravenous contrast injection. Wound disruption pressure measurements. Before the animals were sacrificed and while they were under general anesthesia, wound disruption pressures were determined. A 16gauge angiocatheter was inserted into the bladder dome, and recording pressures were obtained via a Datascope 2000 pressure monitor (Datascope, Paramus, New Jersey) while saline was infused into the bladder with ureters clamped. Tensile analysis procedure. Cystectomy was performed prior to animal sacrifice. The freshly retrieved bladder was crosssectioned into 0.25 inch pieces, cut such that each section contained an intact wound closure surrounded by at least 2 cm.
Eight extravesical ureteral reimplants were performed in four dogs. There were no intra- or postoperative complications. The length of time required for laser welding was 1.5 to 2 minutes and approximated that of hand-sewn closures. Evaluation was performed at 7 (n = 1), 14 (n = 2) and 28 days (n = 1) postoperatively. Prior to sacrifice, intravenous pyelograms indicated bilateral ureteral patency and grossly normal renal function. Comparative measurements of renal function by either renal scanning or creatinine clearance determinations were not performed. At superphysiologic intravesical pressures (>100 cm. H 2 0) there was no evidence of wound disruption in either the laser welded or sutured group. However, at these pressures, disruption of surrounding normal tissue was noted, as evidenced by serosal and muscle layer tearing along the dome and lateral bladder walls. The stress-strain data for laser-welded and sutured bladder tissue is shown in figure 2. At 7 days, the samples were noted to break at the anastomosis in the welded and sutured groups. However, at 14 and 28 days, tissue disruption was noted to occur at points adjacent to the repair in both groups. At each time interval, the laser-welded muscle flaps withstood greater stress (kg. force/cm. 2 ) (2.03, 1.96, 5.81) than did sutured tissue (1.37, 1.45, 2.41). Although these data represent single tissue samples and are not amenable to statistical analysis, laser-welded closures appeared to be stronger at each study interval. In the study group, histologic examination of sections taken through the closure sites revealed a layer of fibrinogen across the tissue gap without evidence of underlying thermal injury. At 7 days postoperatively, the inflammatory reaction at the surgical site was equivalent in the laser-welded and sutured tissue. In both groups, normal healing by granulation tissue and fibrous connective tissue was observed at the site where the bladder tunica muscularis was incised. However, at 14 and 28 days postoperatively, foreign body reaction and ureteral distortion was noted in the control closures, but was absent in the study group (fig. 3). In all cases, the transitional epithelial
Stress - Strain Profile Tension (Kg Force/ cm 7
2 )
1
IU 0
7 Days
14 Days
28 Days
Post Operative Period -- - ~ - - - - - - - - - - - -
~utured Flaps
Ill Lase~ Flap~
l
L ~ --------------
Fm. 2. Tensile strength measurements.
516
LASER TISSUE WELDING IN URETERAL REIMPLANTATION
FIG. 3. Histological examination. Left, appearance of surgical site in sutured closure (control) 14 days postoperatively. Note foreign body reaction in muscularis (above) and underlying ureter al distortion. Right, appearance of surgical site in laser-welded closure 14 days postoperatively.
mucosa lining the urinary bladder and ureters was unremarkable. DISCUSSION
The methods for ureteral reimplantation can be divided broadly into either intravesical or extravesical. Most urologists today prefer the intravesical cross-trigonal reimplantation described by Cohen. 10 The major advantage of the extravesical approach for reimplantation (Lich-Gregoir technique) is that the bladder is not opened during the procedure. The extravesical approach is easily amenable to laparoscopic techniques. Additionally, there appears to be no proven advantage of the intravesical over the extravesical approach in preventing reflux. Atala et al. have successfully performed laparoscopic extravesical reimplants in the porcine model using a hernia stapler to close muscle flaps. 11 Theoretical disadvantages to this approach include possible ureteral occlusion secondary to misplaced staples, foreign body reaction with possible distortion of intramural tunnels and hence obstruction or continued reflux, and, last, potential for differential growth leading to operative failure. These potential disadvantages may be overcome by the use of absorbable staplers designed for this purpose. Laser welding may be a better way of reinforcing such closures. Absorbable staples in selected areas of closure would benefit tissue approximation and make laser-welding more easily performed. Several techniques for laparoscopic tissue closure are in use. Electrocautery, surgical clips and suture ligatures all provide acceptable means of closing small vessels and ducts. However, large incisions are not amenable to such techniques. The endoscopic placement of multiple sutures, to provide water-tightness, is laborious and impractical. Laparoscopically introduced laser welding has been performed experimentally in human biliary tissue and rabbit small bowel, 12 and its use in bladder is reported here. We have shown that laser glue reinforcement of a suture line in experimental models can provide higher leakage pressures than sutures alone. 13- 15 A further advantage of laser welds is their ability to grow with the welded tissue, 16 in contrast to stapled anastomoses and conventional continuous suture closures, which use nonabsorbable material. This provides a theoretical advantage in an organ such as the pediatric bladder in
which relatively rapid growth occurs. Differential tissue growth does not seem to be a factor when absorbable material is used. The use of dye-enhancement (ICG) in fibrinogen glue has been shown to improve selective localization of laser heat with less surrounding tissue injury. 17• 18 This is made possible by the selective absorption peak of ICG, which is approximately 805 nm. An 808 nm. diode laser is used in conjunction with this glue. This wavelength does not cause tissue injury even at the highest outputs (9.6 W/cm. 2 ) in the absence of ICG. 19 In this way underlying or surrounding tissue is not damaged. This is particularly important when applying laser heat energy in the vicinity of the ureter, which may become obstructed from edema resulting from thermal injury. None of the animals in this study showed any evidence of urothelial thermal injury. As the trend toward less invasive procedures continues, laparoscopic urologic surgery will undoubtedly involve laser welding techniques. We contend that laser tissue welding increases tensile strength by decreasing inflammation and allowing more rapid healing. This experiment was designed to show that strong extravesical wound closures can be created safely and easily via laser heat energy. Further studies using the porcine model and laparoscopically introduced laser welding in extravesical reimplantation are underway. REFERENCES 1. Poppas, D. P., Schlossberg, S. M., Richmond, I. L., Gilbert, D. A.
2.
3. 4. 5. 6.
and Devine, C. J.: Laser welding in urethral surgery: improved results with a protein solder. J. Urol., 139: 415, 1989. Burger, R. A., Gerharz, C.-D., Bunn, H., Engelmann, U. H. and Hohenfellner, R.: Laser assisted urethral closure in the rat: comparison of CO 2 and neodymium-YAG laser techniques. J. Urol., 144: 1000, 1990. Merguerian, P.A., Seremetis, G. and Becher, M. W.: Hypospadias repair using laser welding of ventral skin flaps in rabbits: comparison with sutured repair. J. Urol., part 2, 148: 667, 1992. Rosenberg, S. K., Elson, L. and Nathan, L. E., Jr.: Carbon dioxide laser microsurgical vasovasostomy. Urology, 25: 53, 1985. Shanberg, A., Tansey, L., Baghdassarian, R., Sawyer, D. and Lynne, C.: Laser-assisted vasectomy reversal: experience in 32 patients. J. Urol., 143: 528, 1990. Lynne, C. M., Carter, M., Dew, D., Thomsen, S. and Thomsen, C.: Laser-assisted vas anastomosis: a preliminary report. Lasers Surg. Med., 3: 261, 1983.
LASER TISSUE l.NELDING IN URETERAL REIM:PLANTATJ:ON
7. Aldefelder, J., Phiilip, J., Engelmann, U. H. and Senge, T.: Stented laser welded vasovasostomy in the rat: comparison of Nd:YAG and CO, lasers. J. Reconstr. Microsurg., 7: 317, 1991. 8. Merguerian, P. A. and Rabinowitz, R.: Dismembered nonstented uretero-ureterostomy using the carbon dioxide laser in the rabbit: comparison with suture anatomosis. J. Urol., 136: 229, 1986. 9. Gestring, G. F. and Lerner, R.: Autologous fibrinogen for tissue adhesion, hemostasis, and embolization. Vase. Surg., 17: 294, 1983. 10. Cohen, S. J.: Ureterozystoneostomie. Eine neue Atirefluxtechnik. Aktuel Urol.,6: 1, 1975. 11. Atala, A., Goldstein, D.S., Kavoussi, L. R., Retik, A. B. and Peters, C. A.: Laparoscopic anti-reflux surgery. American Pediatric Association, Annual Meeting, October 10-15, 1992, San Francisco, California. abstract: 86, 1992. 12. Sauer, J. S. and Hinshaw, J. R.: A fiber optic exoscope for laser tissue welding. Lasers Surg. Med., 6: 219, 1986. 13. Auteri, J. S., Oz, M. C., Jeevanandam, V., Sanchez, J. A., et al.: Tracheal anastomosis using tissue welding with diode laser energy. J. Invest. Surg., 3: 301, 1990.
517
14. Auteri, J" S., Oz, M. C., Jeevanandam, V., Sanchez, J. A., Treat, M. R. and Smith, C. R.: Laser activation of tissue sealant in hand sewn canine esophageal closure. J. Thorac. Cardiovasc. Surg., (in press). 15. Libutti, S. K., Oz, M. C., Forde, K. A., Auteri, J. S., Johnson, J.P., Bass, L. S. and Treat, M. R.: Canine colonic anastomoses reinforced with dye-enhanced fibrinogen and a diode laser. Surg. Enclose., 4: 97, 1990. 16. Treat, M. R., Oz, M. C. and Bass, L. S.: New technologies and future applications of surgical lasers. Surg. Clin. North Am., 72: 705, 1992. 17. Chuck, R. S., Oz, M. C., Dolhery, T. M., Johnson, J. P., Bass, L. S., Nowygrod, R. and Treat, M. R.: Dye-enhanced laser tissue welding. Lasers Surg. Med., 9: 471, 1989. 18. Oz, M. C., Chuck, R. S., Johnson, J. P., et al.: Indocyanine green dye enhanced vascular welding with the near infrared diode laser. J. Vase. Surg., 11: 718, 1990. 19. Anderson, R. R. and Parrish, J. A.: Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science, 220: 524, 1983.
Vol. 151, 514-517, February 1994
Printed in U.S.A.
PRELIMINARY RESULTS OF LASER TISSUE WELDING IN EXTRAVESICAL REIMPLANTATION OF THE URETERS ANDREW J. KIRSCH, GREGORY E. DEAN, MEHMET C. OZ, STEVEN K. LIBUTTI, MICHAEL R. TREAT, ROMAN NOWYGROD AND TERRY W. HENSLE* From the Department of Urology, Squier Urological Clinic and the Department of Surgery, The Columbia University College of Physicians and Surgeons, New York, New York
ABSTRACT
One exciting potential use of laparoscopic technology is the extravesical reimplantation of the ureters. We have assessed the efficacy of laser-activated fibrinogen solder to close vesical muscle flaps over submucosal ureters (Lich-Gregoir technique) in a canine model. Four dogs were subjected to unilateral flap closures via a protein solder (indocyanine green and fibrinogen) applied to the bladder serosa and exposed to 808 nm. continuous wave diode laser energy. Contralateral reimplantation was performed using 4-zero vicryl muscle flap closures (controls). At 7, 14 and 28 days postoperatively, intravenous pyelograms confirmed bilateral ureteral patency. At intravesical pressures above 100 cm. H20, there was no evidence of wound disruption in either group. Nondisrupted wound closures were sectioned and strained until ultimate breakage to determine tensile strength. At each study interval the laser-welded closures withstood greater stress than the controls. Although these data represent single tissue samples and are not amenable to statistical analysis, laser-welded closures appeared to be stronger at each study interval. In conclusion, laser-welded vesical wound closures appear at least as strong as suture closures in the canine model. KEY WORDS:
ureter, replantation, lasers, laparoscopy
Technological advances in urology and in the whole field of minimally invasive surgery have enabled urologists to diagnose and treat a wide variety of abnormalities via the laparoscopic approach. Although this strategy seems advantageous, many drawbacks exist. Intracorporal tissue closures and anastomoses via the laparoscope are technically difficult. While intracorporal suturing is possible, it remains tedious and time consuming. The use of a laparoscopic gastrointestinal stapler may solve this problem in bowel surgery, but in the urinary tract a finer anastomosis is often necessary, and foreign bodies, such as staples, may lead to urolithiasis and infection. Tissue welding may not only overcome this obstacle but may also expand the number of procedures being done endoscopically. One such use of laser soldering is in ureteral reimplantation. We propose reimplanting ureters via the extravesical approach (Lich-Gregoir technique) using low power laser welding technology for tissue closure. Laser-assisted tissue welding in urologic surgery has been used for primary anastomoses of the urethra, 1- 3 vas deferens4- 7 and ureter, 8 with promising results. To date, no published reports have described the use of such technology in ureteral reimplantation and vesical wound closure. We have assessed laser tissue welding to evaluate its utility in detrusor wound closure and its future laparoscopic application. MATERIALS AND METHODS
Fibrinogen preparation (fibrinogen glue). Human fresh frozen plasma was transferred to test tubes and placed in a freezer at -SOC for at least 12 hours. The tubes were then thawed at 4C and centrifuged at 1000 g for 15 minutes. The supernatant was decanted, leaving the precipitate, fibrinogen. The high viscosity of this solution permits easy manipulation with forceps. Fibrinogen can be stored at -SOC for as long as 1 year. 9 Dye preparation. Indocyanine green dye (5 µg.) (Becton Dickenson, Baltimore, Maryland) was mixed with sterile water to Accepted for publication September 14, 1993. * Requests for reprints: Director, Pediatric Urology, The Babies Hospital, Columbia-Presbyterian Medical Center, 3959 Broadway, New York, New York, 10032. 514
saturation. The half-life of this solution is approximately 10 hours. The dye has an absorption peak at 805 nm. and an absorption coefficient of 2 x 106/m.-1 cm.-1 • Indocyanine green (0.2 ml.) was combined with the fibrinogen glue and mixed 30 minutes before each operation. Laser system. Tissue welding was performed with a diode laser module (System 7200, Spectra-Physics, Mountain View, California) coupled to a hand-held focusing optic. The laser system consists of a phased array of gallium-aluminum-arsenide semiconductor diodes. The major wavelength output of the laser diode is 808 ± 1 nm. Additional bands of laser energy occur in the visible red spectrum and allow the operator to visualize the spot size of the laser during the tissue weld. With the addition of a focusing optic, the beam diameter is 2 mm. at a distance of 4 cm. The focusing optic permits a greater working distance, providing greater visibility of the welded area. Laser power was measured at the output of the focusing optic with a laser power meter (Model 201, Coherent Science Division, Palo Alto, California). Operative procedure. Four conditioned male dogs (ages 3 to 4 years, weighing 26 to 31 kg.) were fasted 24 hours before bilateral extravesical reimplantation. The dogs were anesthetized with pentobarbital (35 mg./kg.) and intubated. Before surgery, a cephalosporin was given intravenously and urinary catheters were placed. The bladder was filled to distention, and a lower midline incision was made. The rectus bellies were retracted exposing the underlying bladder. The superficial fascia overlying the bladder was excised. The ureters were exposed and encircled with Penrose drains. The intramural portion of the distal ureter was separated from the detrusor muscle circumferentially, using a clamp, down to the vesical submucosa. Using a #15 blade, the detrusor muscle was divided down to the submucosa, along the course of the ureter, in the cephalad direction for 2 cm. from the ureter (fig. 1, A). Lateral flaps were created in the bladder muscle against the submucosa to cover the ureter. The ureter was then placed into the groove in contact with the bladder mucosa. The muscle flaps were then closed over the ureter by either interrupted 4-zero vicryl sutures or dye-enhanced (ICG) fibrinogen glue with diode laser (808 nm.)
515
LASER TISSUE WELDING IN URETERAL REIMPLANTATWN
of uninterrupted tissue. Suture material was left intact in the sutured closure group. Each section was tested using a tensile grip applicator (Instron Corporation, Canton, Massachusetts, Table Model 1130 Instron). The bladder tissue was strained perpendicular to the axis of the closure until ultimate breakage. Relevant elastic constants, including modulus and tensile break values, were calculated from the strain profile for each tissue section. Histologic analysis. Freshly obtained unstressed tissue was preserved in 10% formaldehyde solution buffered to physiologic pH for histologic staining with hematoxylin and eosin (H & E). RESULTS
Fm. 1. Operative procedure. A, bladder muscle incised to level of mucosa in cephalad direction. B, conventional rnuscularis flap closure. Muscle edges aligned with single suture. Fibrinogen/indocyanine green (ICG) glue applied. C, laser-welded flap closure.
activation (fig. 1, Band C). The amount of glue required ranged from 2.0 to 3.0 ml. A single stay suture of 4-zero catgut was used to align the muscle flaps in the laser group. The laser was operated on continuous mode output at a power of 300 mW, resulting in a power density of 9.6 W /cm. 2 • Laser energy was applied over the length of the incision until desiccation of the fibrinogen was observed as a green to white color change. The celiotomy incision was then closed in layers. Measurement of renal function and ureteral patency. At 7, 14 and 28 days intravenous pyelograms (IVP) were obtained at 1, 15 and 30 minutes after intravenous contrast injection. Wound disruption pressure measurements. Before the animals were sacrificed and while they were under general anesthesia, wound disruption pressures were determined. A 16gauge angiocatheter was inserted into the bladder dome, and recording pressures were obtained via a Datascope 2000 pressure monitor (Datascope, Paramus, New Jersey) while saline was infused into the bladder with ureters clamped. Tensile analysis procedure. Cystectomy was performed prior to animal sacrifice. The freshly retrieved bladder was crosssectioned into 0.25 inch pieces, cut such that each section contained an intact wound closure surrounded by at least 2 cm.
Eight extravesical ureteral reimplants were performed in four dogs. There were no intra- or postoperative complications. The length of time required for laser welding was 1.5 to 2 minutes and approximated that of hand-sewn closures. Evaluation was performed at 7 (n = 1), 14 (n = 2) and 28 days (n = 1) postoperatively. Prior to sacrifice, intravenous pyelograms indicated bilateral ureteral patency and grossly normal renal function. Comparative measurements of renal function by either renal scanning or creatinine clearance determinations were not performed. At superphysiologic intravesical pressures (>100 cm. H 2 0) there was no evidence of wound disruption in either the laser welded or sutured group. However, at these pressures, disruption of surrounding normal tissue was noted, as evidenced by serosal and muscle layer tearing along the dome and lateral bladder walls. The stress-strain data for laser-welded and sutured bladder tissue is shown in figure 2. At 7 days, the samples were noted to break at the anastomosis in the welded and sutured groups. However, at 14 and 28 days, tissue disruption was noted to occur at points adjacent to the repair in both groups. At each time interval, the laser-welded muscle flaps withstood greater stress (kg. force/cm. 2 ) (2.03, 1.96, 5.81) than did sutured tissue (1.37, 1.45, 2.41). Although these data represent single tissue samples and are not amenable to statistical analysis, laser-welded closures appeared to be stronger at each study interval. In the study group, histologic examination of sections taken through the closure sites revealed a layer of fibrinogen across the tissue gap without evidence of underlying thermal injury. At 7 days postoperatively, the inflammatory reaction at the surgical site was equivalent in the laser-welded and sutured tissue. In both groups, normal healing by granulation tissue and fibrous connective tissue was observed at the site where the bladder tunica muscularis was incised. However, at 14 and 28 days postoperatively, foreign body reaction and ureteral distortion was noted in the control closures, but was absent in the study group (fig. 3). In all cases, the transitional epithelial
Stress - Strain Profile Tension (Kg Force/ cm 7
2 )
1
IU 0
7 Days
14 Days
28 Days
Post Operative Period -- - ~ - - - - - - - - - - - -
~utured Flaps
Ill Lase~ Flap~
l
L ~ --------------
Fm. 2. Tensile strength measurements.
516
LASER TISSUE WELDING IN URETERAL REIMPLANTATION
FIG. 3. Histological examination. Left, appearance of surgical site in sutured closure (control) 14 days postoperatively. Note foreign body reaction in muscularis (above) and underlying ureter al distortion. Right, appearance of surgical site in laser-welded closure 14 days postoperatively.
mucosa lining the urinary bladder and ureters was unremarkable. DISCUSSION
The methods for ureteral reimplantation can be divided broadly into either intravesical or extravesical. Most urologists today prefer the intravesical cross-trigonal reimplantation described by Cohen. 10 The major advantage of the extravesical approach for reimplantation (Lich-Gregoir technique) is that the bladder is not opened during the procedure. The extravesical approach is easily amenable to laparoscopic techniques. Additionally, there appears to be no proven advantage of the intravesical over the extravesical approach in preventing reflux. Atala et al. have successfully performed laparoscopic extravesical reimplants in the porcine model using a hernia stapler to close muscle flaps. 11 Theoretical disadvantages to this approach include possible ureteral occlusion secondary to misplaced staples, foreign body reaction with possible distortion of intramural tunnels and hence obstruction or continued reflux, and, last, potential for differential growth leading to operative failure. These potential disadvantages may be overcome by the use of absorbable staplers designed for this purpose. Laser welding may be a better way of reinforcing such closures. Absorbable staples in selected areas of closure would benefit tissue approximation and make laser-welding more easily performed. Several techniques for laparoscopic tissue closure are in use. Electrocautery, surgical clips and suture ligatures all provide acceptable means of closing small vessels and ducts. However, large incisions are not amenable to such techniques. The endoscopic placement of multiple sutures, to provide water-tightness, is laborious and impractical. Laparoscopically introduced laser welding has been performed experimentally in human biliary tissue and rabbit small bowel, 12 and its use in bladder is reported here. We have shown that laser glue reinforcement of a suture line in experimental models can provide higher leakage pressures than sutures alone. 13- 15 A further advantage of laser welds is their ability to grow with the welded tissue, 16 in contrast to stapled anastomoses and conventional continuous suture closures, which use nonabsorbable material. This provides a theoretical advantage in an organ such as the pediatric bladder in
which relatively rapid growth occurs. Differential tissue growth does not seem to be a factor when absorbable material is used. The use of dye-enhancement (ICG) in fibrinogen glue has been shown to improve selective localization of laser heat with less surrounding tissue injury. 17• 18 This is made possible by the selective absorption peak of ICG, which is approximately 805 nm. An 808 nm. diode laser is used in conjunction with this glue. This wavelength does not cause tissue injury even at the highest outputs (9.6 W/cm. 2 ) in the absence of ICG. 19 In this way underlying or surrounding tissue is not damaged. This is particularly important when applying laser heat energy in the vicinity of the ureter, which may become obstructed from edema resulting from thermal injury. None of the animals in this study showed any evidence of urothelial thermal injury. As the trend toward less invasive procedures continues, laparoscopic urologic surgery will undoubtedly involve laser welding techniques. We contend that laser tissue welding increases tensile strength by decreasing inflammation and allowing more rapid healing. This experiment was designed to show that strong extravesical wound closures can be created safely and easily via laser heat energy. Further studies using the porcine model and laparoscopically introduced laser welding in extravesical reimplantation are underway. REFERENCES 1. Poppas, D. P., Schlossberg, S. M., Richmond, I. L., Gilbert, D. A.
2.
3. 4. 5. 6.
and Devine, C. J.: Laser welding in urethral surgery: improved results with a protein solder. J. Urol., 139: 415, 1989. Burger, R. A., Gerharz, C.-D., Bunn, H., Engelmann, U. H. and Hohenfellner, R.: Laser assisted urethral closure in the rat: comparison of CO 2 and neodymium-YAG laser techniques. J. Urol., 144: 1000, 1990. Merguerian, P.A., Seremetis, G. and Becher, M. W.: Hypospadias repair using laser welding of ventral skin flaps in rabbits: comparison with sutured repair. J. Urol., part 2, 148: 667, 1992. Rosenberg, S. K., Elson, L. and Nathan, L. E., Jr.: Carbon dioxide laser microsurgical vasovasostomy. Urology, 25: 53, 1985. Shanberg, A., Tansey, L., Baghdassarian, R., Sawyer, D. and Lynne, C.: Laser-assisted vasectomy reversal: experience in 32 patients. J. Urol., 143: 528, 1990. Lynne, C. M., Carter, M., Dew, D., Thomsen, S. and Thomsen, C.: Laser-assisted vas anastomosis: a preliminary report. Lasers Surg. Med., 3: 261, 1983.
LASER TISSUE l.NELDING IN URETERAL REIM:PLANTATJ:ON
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