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Transurethral neodymium:YAG laser surgery for bladder tumors
TRANSURETHRAL
NEODYMIUM:YAG
SURGERY FOR BLADDER KIYOKI HIROSHI
OKADA,
LASER
TUMORS
M.D.
ASAOKA,
M.D.
TATSUO AMAGAI, M.D. YASUHIKO ONOE, M.D. TAKASHI
KISHIMOTO,
M.D.
From the Department of Urology, Nihon School of Medicine, Tokyo, Japan
University
neoABSTRACT - Forty-f;ve patients with 63 bladder tumors were treated, with transurethral dymium:YAG laser irradiation. The operation was per$ormed under lumbar or local anesthesia, the bladder being irrigated with a 10 per cent urigal solution. A five-second beam of SO-watt electric power was chosen as one unit of irradiation, and 5 to 50 units of irradiation were utilized for one operation. Forty-one tumors were completely resected with laser irradiation alone. In the other 22 tumors, electroresection or partial cystectomy was undertaken after the laser irradiation. Pronounced complications did not develop in any of the patients. Perforation was not experienced in our series. The bleeding at irradiation was minimal. Laser surge y through endoscopy thus represents a promising approach for the treatment of bladder tumors.
Since Maiman’ developed the practical use of the laser beam, it has been utilized for various fields. Laser is an abbreviation of light amplification by stimulated emission of radiation. Because laser produces a coherent beam-defined wavelength and emits strong energy in a small area, medical employment of laser has also been undertaken for diagnosis and treatment. In the urologic field, several kinds of laser beams (i.e., carbon dioxide [CO21 laser,2 argon laser,3 and neodymium:YAG (Nd:YAG) laser4a5) have been used for the treatment of bladder tumors and urethral stenosis. With the development of a flexible delivery system,6 it became possible to transmit Nd:YAG laser light through quartz fiber, making it feasible to perform transurethral laser surgery. Herein, we report the results of the Nd:YAG laser on bladder tumors through endoscopy.
404
Material
and Methods
Forty-five patients with 63 bladder tumors were treated with transurethral Nd:YAG laser irradiation. Their ages ranged from thirty-four to eighty-two years. The sex distribution was 40 males and 5 females. The tumors were classified by their characteristics into 42 small tumors less than 1 cm in diameter and 21 medium-sized tumors 1 to 3 cm in diameter, as well as 50 pedunculated and 13 sessile tumors. Three tumors were located in the bladder neck, 10 in the trigone, 30 in the posterior wall, 16 in the lateral wall, 8 in the dome, and 5 in the anterior wall. Of these patients 36 were classified as Ta and Tl, and 9 as T2. Clinicopathologic findings showed 29 of grade 1, 10 grade 2. and 3 grade 3. The equipment employed for laser surgery was a MediLas YAG and Wolf Laser Cystoscope.
UROLOGY
/
OCTOBER
1982
/
VOLUME
XX,
NUMBER
4
Reservoir
The transurethral laser operation was performed while irrigating the bladder with a 10 per cent urigal solution. Lumbar anesthesia was used in 37 cases and local anesthesia in 8. A five-second beam of SO-watt electric power was chosen as one unit of irradiation, and 5 to 50 units of irradiation were utilized for one operation. Forty-one tumors were completely resected with laser irradiation alone. In the other 22 tumors, electroresection or partial cystectomy was undertaken after laser surgery. Results Transurethral Nd:YAG laser has been applied for the last two years for the treatment of bladder tumors at the Department of Urology, Nihon IJniversity (Fig. 1). Prior to this, the Helium Neon (HeNe) laser beam was used as a pilot beam. We used a water-filled bladder system. During the manipulation in the laser treatment, overstretching of the bladder should be avoided, as is the case with the currently available transcrethral electroresection. Irradiation was done from the surface of the tumor at a distance of 3 to 5 mm between the tip cC the instrument and the tumor. In cases of pedunculated tumors, it was often possible to irradiate directly to the pedicle of the tumor from the lateral side. Irradiation induces white degeneration of the tumor without damage to surrounding tissues. Minor bleeding often occurred with the rupture of small vessels. However, hemostasis could be accomplished by additional units of Nd:YAG beams. Some of the tumors were completely destroyed by one operation. In most instances, the white coat appeared only in the superficial lesion of the tumor immediately after the operation. Following this, complete necrotization occurred one week after the operation with the presence of mucosal injection and edema, which gradually became normal epithelium within two weeks.
TABLE
FIGURE
1.
Schema of transurethral
The results of the laser operation were analyzed according to the tumor size, characteristics, location, and histopathology. With regard to tumor size, 37 of 42 small tumors (88%) could be eradicated by laser irradiation alone, but medium-sized tumors were difficult to treat in this manner. Seventeen of 21 mediumsized tumors needed to be treated with combination therapy. As to tumor characteristics, 37 of 50 pedunculated tumors (74%) could be destroyed with laser therapy alone, while 9 of 13 sessile tumors were treated with a combination of laser and other therapy (Table I). As far as the locations of the tumors were concerned, it is difficult to evaluate the efficacy of laser surgery from our data. Albarrantype endoscope is able to direct the laser beam to the entire area of the bladder wall, but it is our impression that it is rather difficult to irradiate the tumors at the anterior wall, dome, and bladder neck (Table II). With regard to staging, 22 of 36 cases of Ta and Tl (61%) underwent the laser operation, but most of the T2 cases required laser therapy as well as
Results of laser therapy
I.
TABLE
Results of laser therapy
II.
Laser
Tumor
Alone*
Small tumor Medium tumor
37 (88)
X’edunculated !iessile TOTALS *Numbers
UROLOGY
Combination
4 (19)
Total
5
42
17
21
37 (74) 4 (31)
13 9
50 13
41
22
63
in parentheses
indicate
/
1982
OCTOBER
Site Neck Trigone Posterior Lateral Dome Anterior
per cent.
/
VOLUME
XX,
NUMBER
laser operation.
4
Laser Alone 2 8 15
Combination 1 2 15
9 6 3
i 2
Total 3 10
30 16 8 5
105
FIGURE 2. Laser irradiation orijice. (B) After application
bladder tumor. (A) Pedunculated 1,250 joules of laser beam to bladder
of of
electroresection. With respect to the grading of the tumor, grades 2 and 3 cases tended to be treated by combination therapy rather than laser therapy alone. As to the prognosis of the cases reported herein, 34 of the 45 cases had no recurrence during a follow-up period of from four to twentytwo months. Recurrence was observed in 11 cases with a follow-up period of two to thirteen months, most frequently in medium-sized, sessile tumors, and those in the dome area. Among the 23 patients who underwent laser therapy alone, 3 experienced recurrence. Recurrence was noted in 8 of the 22 patients undergoing combination therapy. This was mainly due to technical inexperience. Case Report An eighty-two-year-old woman was admitted because of macrohematuria. Cystoscopy revealed a small-sized, almost 1 cm in diameter, pedunculated papillary tumor at the right ureteral orifice (Fig. 2A). Clinical diagnosis of Tl tumor was made according to bimanual palpation, cystoscopy, intravenous pyelography, cystography, and punch biopsy. Laser irradiation was performed under lumbar anesthesia to the pedicle of the tumor. Five units (total 1,250 joules) of laser beam were irradiated directly at the pedicle of the tumor from the lateral side. After the tumor was peeled off, the base of the bladder tumor was also irradiated by the additional beams (500 joules) to eradicate the remaining tumor cells (Fig. 2B).
406
papillary tumor and 500 joules
at site of right ureteral to base of tumor.
Comment Several kinds of laser, i.e., Ruby, CO2, argon, and Nd:YAG laser, have been applied for the treatment of bladder tumors and urethral stenosis. The first report of laser experiments in the field of urology was that of Parsons et al. in 1966. ’ They tried to irradiate Ruby laser beam at different energy levels to the dog bladder under simulated cystoscopic conditions. On histologic examination they clarified that irradiation induced cell destruction of the bladder mucosa, and regeneration occurred at seven to ten days. After that, Mulvaney and Beck6 demonstrated the treatment of urinary calculi with a single impact of the CO2 laser in vitro. They suggested that fracture and destruction of calculi would be possible as a result of irradiation by a CO2 laser. They also performed partial nephrectomy of dog kidneys with a CO2 laser and mentioned that the action of cutting was slow and hemostasis was unsatisfactory using a 50-watt output. Therefore, they could not obtain favorable results. On the other hand, since flexible delivery system was developed by Nath et al. in 1973,6 it became possible to transmit argon as well as Nd:YAG laser beam through quartz fiber. Therefore, the argon and Nd:YAG lasers have been promising possibilities for transurethral manipulation with the use of flexible fiber. Rothauge, Kraushaar, and N&keg treated 34 patients with 41 bladder tumors transurethrally with a 15-watt argon laser. They stated that the advantages of argon laser were minimal bleeding
UROLOGY
/ OCTOBER1982
/ VOLUMEXX,NUMBER4
and few relapses. Staehler and others demonstrated that Nd:YAG irradiation caused homogenous necrosis with the uniform distribution of the heats to the bladder tissues, so-called popcorn effects. 4,10,11According to the results of their experiments, they concluded Nd:YAG laser was superior to CO2 laser or argon laser for the treatment of bladder tumor. Clinical application with Nd:YAG laser was also performed on the 69 patients with 110 tumors. l1 They reported that indications for Nd:YAG laser were not only small tumors but also large tumors previously resected by electrical loop, and laser irradiation to the tumor bed after the conventional transurethral electroresection was especially useful for the destruction of intramural tumor cells. Three hundred two small tumors were treated by Hofstetter et ~1.~ with Nd:YAG laser, and 196 larger tumors were irradiated after electroresection as mentioned by Staehler. 4 They stated that the advantages of the laser were no bleeding, no perforation of the bladder, no anesthesia, and short operation, and indications were multiple, small, wide-spread growing tumors, especially on the bladder back wall. Previously, we attempted laboratory experiments to clarify the extent of tissue damage by the Nd:YAG laser.r2 Rat bladders were irrigated with isotonic saline and irradiated with a laser beam at different energy levels after being exposed under pentobarbital sodium (Nembutal) anesthesia. On histologic examination, the rat bladders revealed defined tissue damage, the extent of which varied according to the irradiation time and power. High-power and short-time irradiation induced severe damage to the bladder tissue more than low-power and long irradiation of the same energy. As a result of the laboratory experiment, five-second and 50-watt electric power was chosen for the laser therapy. From our present clinical experiences, we offer the following remarks: (1) Transurethral Nd:YAG laser surgery could be performed with local anesthesia. Thus, it can be applied for the patients with severe complications, such as cardiovascular or cerebrovascular diseases. (2)
UROLOGY
/
OCTOBER
1982
/
VOLUME
XX,
NUMBER
Only minimal or no bleeding occurred during operation. Even when bleeding occurred, hemostasis was managed easily with additional irradiation. (3) Complications were rare. We have never experienced perforation of either bladder or intestine. (4) Obturator nerve reflex does not occur with laser irradiation. (5) In 11 of 45 cases, tumor recurrence appeared at between two and thirteen months. (6) Our indication of the bladder tumors for laser surgery is only limited to small tumors less than 1 cm in diameter. It was difficult to treat T2 tumors, large tumors, and those in the anterior wall with laser irradiation. As more technical experience is gained, it may become possible to treat these tumors with laser surgery. 30-1, Oyaguchi, Itabashi-ku, Tokyo, Japan, #173 (DR. OKADA) References 1. Maiman TH: Stimulated optical radiation in Ruby, Nature 187: 493 (1960). 2. Willscher MK, Filoso AM, Jako CJ, and Olsson CA: Development of a carbon dioxide laser cystoscope, J Ural 119: 292 (1978). 3. Rothauge CF: Urethroscopic recanalization of urethral stenosis using argon laser, Urology 16: I.58 (1980). 4. Staehler G, and Hofstetter A: Transurethral laser irradiation of urinary bladder tumors, Eur Urol 5: 64 (1979). 5. Hofstetter A, Frank F, Keiditsch E, and Bowering R: Endoscopic neodymium-YAG laser application for destroying bladder tumors. ibid 7: 278 (1981). 6. Nath G, dorisch W, Kreitmair A, and Kieflhaber P: Transmission of a powerful argon laser beam through a fiber optic flexible gastroscopy, Endoscopy 5: 213 (1973). 7. Parsons RL, et al: The effect of the laser on dog bladders: a preliminary report, J Urol 95: 716 (1966). 8. Mufvaney WP, and Beck CW: The laser beam in urology, ibid QQ: 112 (1968). 9. Rothauge CF, Kraushaar J, and Noske HD: Einjahrige Erfahrungen mit der transurethralen Laser therapie des Harnblasentumors. Vorlaufig Mitteilung, Munch Med Wschr 119: 593 (1977). 10. Staehler G, et al: Endoscopy in experimental urology using an argon laser beam, Endoscopy 8: 1 (1976). 11. Staehler G, Halldorsson Th, Langerholc J, and Bilgram R: Endoscopic applications of the Nd:YAG laser in urology: theory, results, dosimetry, Urol Res 9: 45 (1981). 12. Amagai T: Experimental and clinical studies for laser application to the treatment of bladder tumor, Nihon Univ J Med 40: 985 (1981).
4
407
NEODYMIUM:YAG
SURGERY FOR BLADDER KIYOKI HIROSHI
OKADA,
LASER
TUMORS
M.D.
ASAOKA,
M.D.
TATSUO AMAGAI, M.D. YASUHIKO ONOE, M.D. TAKASHI
KISHIMOTO,
M.D.
From the Department of Urology, Nihon School of Medicine, Tokyo, Japan
University
neoABSTRACT - Forty-f;ve patients with 63 bladder tumors were treated, with transurethral dymium:YAG laser irradiation. The operation was per$ormed under lumbar or local anesthesia, the bladder being irrigated with a 10 per cent urigal solution. A five-second beam of SO-watt electric power was chosen as one unit of irradiation, and 5 to 50 units of irradiation were utilized for one operation. Forty-one tumors were completely resected with laser irradiation alone. In the other 22 tumors, electroresection or partial cystectomy was undertaken after the laser irradiation. Pronounced complications did not develop in any of the patients. Perforation was not experienced in our series. The bleeding at irradiation was minimal. Laser surge y through endoscopy thus represents a promising approach for the treatment of bladder tumors.
Since Maiman’ developed the practical use of the laser beam, it has been utilized for various fields. Laser is an abbreviation of light amplification by stimulated emission of radiation. Because laser produces a coherent beam-defined wavelength and emits strong energy in a small area, medical employment of laser has also been undertaken for diagnosis and treatment. In the urologic field, several kinds of laser beams (i.e., carbon dioxide [CO21 laser,2 argon laser,3 and neodymium:YAG (Nd:YAG) laser4a5) have been used for the treatment of bladder tumors and urethral stenosis. With the development of a flexible delivery system,6 it became possible to transmit Nd:YAG laser light through quartz fiber, making it feasible to perform transurethral laser surgery. Herein, we report the results of the Nd:YAG laser on bladder tumors through endoscopy.
404
Material
and Methods
Forty-five patients with 63 bladder tumors were treated with transurethral Nd:YAG laser irradiation. Their ages ranged from thirty-four to eighty-two years. The sex distribution was 40 males and 5 females. The tumors were classified by their characteristics into 42 small tumors less than 1 cm in diameter and 21 medium-sized tumors 1 to 3 cm in diameter, as well as 50 pedunculated and 13 sessile tumors. Three tumors were located in the bladder neck, 10 in the trigone, 30 in the posterior wall, 16 in the lateral wall, 8 in the dome, and 5 in the anterior wall. Of these patients 36 were classified as Ta and Tl, and 9 as T2. Clinicopathologic findings showed 29 of grade 1, 10 grade 2. and 3 grade 3. The equipment employed for laser surgery was a MediLas YAG and Wolf Laser Cystoscope.
UROLOGY
/
OCTOBER
1982
/
VOLUME
XX,
NUMBER
4
Reservoir
The transurethral laser operation was performed while irrigating the bladder with a 10 per cent urigal solution. Lumbar anesthesia was used in 37 cases and local anesthesia in 8. A five-second beam of SO-watt electric power was chosen as one unit of irradiation, and 5 to 50 units of irradiation were utilized for one operation. Forty-one tumors were completely resected with laser irradiation alone. In the other 22 tumors, electroresection or partial cystectomy was undertaken after laser surgery. Results Transurethral Nd:YAG laser has been applied for the last two years for the treatment of bladder tumors at the Department of Urology, Nihon IJniversity (Fig. 1). Prior to this, the Helium Neon (HeNe) laser beam was used as a pilot beam. We used a water-filled bladder system. During the manipulation in the laser treatment, overstretching of the bladder should be avoided, as is the case with the currently available transcrethral electroresection. Irradiation was done from the surface of the tumor at a distance of 3 to 5 mm between the tip cC the instrument and the tumor. In cases of pedunculated tumors, it was often possible to irradiate directly to the pedicle of the tumor from the lateral side. Irradiation induces white degeneration of the tumor without damage to surrounding tissues. Minor bleeding often occurred with the rupture of small vessels. However, hemostasis could be accomplished by additional units of Nd:YAG beams. Some of the tumors were completely destroyed by one operation. In most instances, the white coat appeared only in the superficial lesion of the tumor immediately after the operation. Following this, complete necrotization occurred one week after the operation with the presence of mucosal injection and edema, which gradually became normal epithelium within two weeks.
TABLE
FIGURE
1.
Schema of transurethral
The results of the laser operation were analyzed according to the tumor size, characteristics, location, and histopathology. With regard to tumor size, 37 of 42 small tumors (88%) could be eradicated by laser irradiation alone, but medium-sized tumors were difficult to treat in this manner. Seventeen of 21 mediumsized tumors needed to be treated with combination therapy. As to tumor characteristics, 37 of 50 pedunculated tumors (74%) could be destroyed with laser therapy alone, while 9 of 13 sessile tumors were treated with a combination of laser and other therapy (Table I). As far as the locations of the tumors were concerned, it is difficult to evaluate the efficacy of laser surgery from our data. Albarrantype endoscope is able to direct the laser beam to the entire area of the bladder wall, but it is our impression that it is rather difficult to irradiate the tumors at the anterior wall, dome, and bladder neck (Table II). With regard to staging, 22 of 36 cases of Ta and Tl (61%) underwent the laser operation, but most of the T2 cases required laser therapy as well as
Results of laser therapy
I.
TABLE
Results of laser therapy
II.
Laser
Tumor
Alone*
Small tumor Medium tumor
37 (88)
X’edunculated !iessile TOTALS *Numbers
UROLOGY
Combination
4 (19)
Total
5
42
17
21
37 (74) 4 (31)
13 9
50 13
41
22
63
in parentheses
indicate
/
1982
OCTOBER
Site Neck Trigone Posterior Lateral Dome Anterior
per cent.
/
VOLUME
XX,
NUMBER
laser operation.
4
Laser Alone 2 8 15
Combination 1 2 15
9 6 3
i 2
Total 3 10
30 16 8 5
105
FIGURE 2. Laser irradiation orijice. (B) After application
bladder tumor. (A) Pedunculated 1,250 joules of laser beam to bladder
of of
electroresection. With respect to the grading of the tumor, grades 2 and 3 cases tended to be treated by combination therapy rather than laser therapy alone. As to the prognosis of the cases reported herein, 34 of the 45 cases had no recurrence during a follow-up period of from four to twentytwo months. Recurrence was observed in 11 cases with a follow-up period of two to thirteen months, most frequently in medium-sized, sessile tumors, and those in the dome area. Among the 23 patients who underwent laser therapy alone, 3 experienced recurrence. Recurrence was noted in 8 of the 22 patients undergoing combination therapy. This was mainly due to technical inexperience. Case Report An eighty-two-year-old woman was admitted because of macrohematuria. Cystoscopy revealed a small-sized, almost 1 cm in diameter, pedunculated papillary tumor at the right ureteral orifice (Fig. 2A). Clinical diagnosis of Tl tumor was made according to bimanual palpation, cystoscopy, intravenous pyelography, cystography, and punch biopsy. Laser irradiation was performed under lumbar anesthesia to the pedicle of the tumor. Five units (total 1,250 joules) of laser beam were irradiated directly at the pedicle of the tumor from the lateral side. After the tumor was peeled off, the base of the bladder tumor was also irradiated by the additional beams (500 joules) to eradicate the remaining tumor cells (Fig. 2B).
406
papillary tumor and 500 joules
at site of right ureteral to base of tumor.
Comment Several kinds of laser, i.e., Ruby, CO2, argon, and Nd:YAG laser, have been applied for the treatment of bladder tumors and urethral stenosis. The first report of laser experiments in the field of urology was that of Parsons et al. in 1966. ’ They tried to irradiate Ruby laser beam at different energy levels to the dog bladder under simulated cystoscopic conditions. On histologic examination they clarified that irradiation induced cell destruction of the bladder mucosa, and regeneration occurred at seven to ten days. After that, Mulvaney and Beck6 demonstrated the treatment of urinary calculi with a single impact of the CO2 laser in vitro. They suggested that fracture and destruction of calculi would be possible as a result of irradiation by a CO2 laser. They also performed partial nephrectomy of dog kidneys with a CO2 laser and mentioned that the action of cutting was slow and hemostasis was unsatisfactory using a 50-watt output. Therefore, they could not obtain favorable results. On the other hand, since flexible delivery system was developed by Nath et al. in 1973,6 it became possible to transmit argon as well as Nd:YAG laser beam through quartz fiber. Therefore, the argon and Nd:YAG lasers have been promising possibilities for transurethral manipulation with the use of flexible fiber. Rothauge, Kraushaar, and N&keg treated 34 patients with 41 bladder tumors transurethrally with a 15-watt argon laser. They stated that the advantages of argon laser were minimal bleeding
UROLOGY
/ OCTOBER1982
/ VOLUMEXX,NUMBER4
and few relapses. Staehler and others demonstrated that Nd:YAG irradiation caused homogenous necrosis with the uniform distribution of the heats to the bladder tissues, so-called popcorn effects. 4,10,11According to the results of their experiments, they concluded Nd:YAG laser was superior to CO2 laser or argon laser for the treatment of bladder tumor. Clinical application with Nd:YAG laser was also performed on the 69 patients with 110 tumors. l1 They reported that indications for Nd:YAG laser were not only small tumors but also large tumors previously resected by electrical loop, and laser irradiation to the tumor bed after the conventional transurethral electroresection was especially useful for the destruction of intramural tumor cells. Three hundred two small tumors were treated by Hofstetter et ~1.~ with Nd:YAG laser, and 196 larger tumors were irradiated after electroresection as mentioned by Staehler. 4 They stated that the advantages of the laser were no bleeding, no perforation of the bladder, no anesthesia, and short operation, and indications were multiple, small, wide-spread growing tumors, especially on the bladder back wall. Previously, we attempted laboratory experiments to clarify the extent of tissue damage by the Nd:YAG laser.r2 Rat bladders were irrigated with isotonic saline and irradiated with a laser beam at different energy levels after being exposed under pentobarbital sodium (Nembutal) anesthesia. On histologic examination, the rat bladders revealed defined tissue damage, the extent of which varied according to the irradiation time and power. High-power and short-time irradiation induced severe damage to the bladder tissue more than low-power and long irradiation of the same energy. As a result of the laboratory experiment, five-second and 50-watt electric power was chosen for the laser therapy. From our present clinical experiences, we offer the following remarks: (1) Transurethral Nd:YAG laser surgery could be performed with local anesthesia. Thus, it can be applied for the patients with severe complications, such as cardiovascular or cerebrovascular diseases. (2)
UROLOGY
/
OCTOBER
1982
/
VOLUME
XX,
NUMBER
Only minimal or no bleeding occurred during operation. Even when bleeding occurred, hemostasis was managed easily with additional irradiation. (3) Complications were rare. We have never experienced perforation of either bladder or intestine. (4) Obturator nerve reflex does not occur with laser irradiation. (5) In 11 of 45 cases, tumor recurrence appeared at between two and thirteen months. (6) Our indication of the bladder tumors for laser surgery is only limited to small tumors less than 1 cm in diameter. It was difficult to treat T2 tumors, large tumors, and those in the anterior wall with laser irradiation. As more technical experience is gained, it may become possible to treat these tumors with laser surgery. 30-1, Oyaguchi, Itabashi-ku, Tokyo, Japan, #173 (DR. OKADA) References 1. Maiman TH: Stimulated optical radiation in Ruby, Nature 187: 493 (1960). 2. Willscher MK, Filoso AM, Jako CJ, and Olsson CA: Development of a carbon dioxide laser cystoscope, J Ural 119: 292 (1978). 3. Rothauge CF: Urethroscopic recanalization of urethral stenosis using argon laser, Urology 16: I.58 (1980). 4. Staehler G, and Hofstetter A: Transurethral laser irradiation of urinary bladder tumors, Eur Urol 5: 64 (1979). 5. Hofstetter A, Frank F, Keiditsch E, and Bowering R: Endoscopic neodymium-YAG laser application for destroying bladder tumors. ibid 7: 278 (1981). 6. Nath G, dorisch W, Kreitmair A, and Kieflhaber P: Transmission of a powerful argon laser beam through a fiber optic flexible gastroscopy, Endoscopy 5: 213 (1973). 7. Parsons RL, et al: The effect of the laser on dog bladders: a preliminary report, J Urol 95: 716 (1966). 8. Mufvaney WP, and Beck CW: The laser beam in urology, ibid QQ: 112 (1968). 9. Rothauge CF, Kraushaar J, and Noske HD: Einjahrige Erfahrungen mit der transurethralen Laser therapie des Harnblasentumors. Vorlaufig Mitteilung, Munch Med Wschr 119: 593 (1977). 10. Staehler G, et al: Endoscopy in experimental urology using an argon laser beam, Endoscopy 8: 1 (1976). 11. Staehler G, Halldorsson Th, Langerholc J, and Bilgram R: Endoscopic applications of the Nd:YAG laser in urology: theory, results, dosimetry, Urol Res 9: 45 (1981). 12. Amagai T: Experimental and clinical studies for laser application to the treatment of bladder tumor, Nihon Univ J Med 40: 985 (1981).
4
407