|Year : 2000 | Volume
| Issue : 1 | Page : 37-40
Advantages of fulguration of posterior urethral valves by Nd: YAG laser
DK Gupta, M Bajpai, AR Charles, M Srinivas, S Dave, A Lal, AK Gupta
Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi, India
D K Gupta
Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Posterior Urethral Valves (PUV) are one of the commonest urolgical problems seen in children and the electrocoagulation, which is the most widely preferred modality to ablate the valves, may not be feasible in small-for-date and low-birth-weight neonates as the suitable size resectoscope/cystoscope may not available. With the availability of Nd: YAG laser at our institute recently, we started performing the laser fulguration instead of electrocoagulation of the valves. We reviewed our experience with the emerging role of the Nd: YAG laser in the fulguration of PUV, comparing the results with a historical control group who underwent the classical electrocoagulation of the PUV. The boys (n=50) diagnosed to have PUV by VCUG were confirmed by Wolf 8.5 size cystoscope, underwent Nd: YAG laser fulguration of the valves with a bare fiber, as a day-care procedure without postoperative catheterization. Historical controls (n=50) who had undergone classical electrocoagulation using 9.5 size Wolf resectoscope served as the controls. The mean age was 1.3 y and 2.6 y in laser and electrocoagulation group respectively. The mean hospital stay of the electrocoagulation group was 3.8 d. Three patients after electrocoagulation developed hematuria and 4 required refulguration whereas in the laser group 5 required refulguration and none developed hematuria. In conclusion, endoscopic laser fulguration of PUV is technically feasible even in neonates and small children. Laser offers excellent results that are comparable to the time-honored electrocoagulation procedure. This has the additional advantage forfulgurating the PUV in smaller caliber urethra as this can be performed with the smaller available cystoscope that has a side channel, admitting the laser fiber.
Keywords: Urethral Valve; Child; Laser; Electrocoagulation; Complication.
|How to cite this article:|
Gupta D K, Bajpai M, Charles A R, Srinivas M, Dave S, Lal A, Gupta A K. Advantages of fulguration of posterior urethral valves by Nd: YAG laser. Indian J Urol 2000;17:37-40
|How to cite this URL:|
Gupta D K, Bajpai M, Charles A R, Srinivas M, Dave S, Lal A, Gupta A K. Advantages of fulguration of posterior urethral valves by Nd: YAG laser. Indian J Urol [serial online] 2000 [cited 2019 May 20];17:37-40. Available from: http://www.indianjurol.com/text.asp?2000/17/1/37/41011
| Introduction|| |
Posterior Urethral Valves (PUV) are one of the most common urological problems having wide clinical implications and the prognosis depends upon the extent of the renal injury inflicted by the time of initiation of intervention and hence earlier the treatment, better the long-term outcome. The management of these valves has changed over the years from avulsion techniques,  open resection,  prolonged catheterisation,  fluoroscopy-guided hook ablation  to the electrocoagulation.  The Neodymium: yttrium-aluminum-garnet (Nd: YAG) laser has an established place in Urology and has become a common tool for treatment of various adult urology diseases.  However, its use in pediatric urology is still limited. The electrocoagulation is the most preferred treatment of PUV all over the world. However, at our center, with the available electrocoagulation unit (9.5 size resectoscope) we faced a unique problem to negotiate the resectoscope into the needy newborns' urethra in a substantial proportion of the babies who were small for date, low birth weight, or the babies with PUV having growth retardation. Such neonates were offered the initial diversion thus necessitating a delay for the definitive fulguration. However, the Nd: YAG laser has obviated this problem by allowing cystoscopy and fulguration of PUV even in the low-birth-weight neonates as this can be negotiated through the side channel of the 8.5 cystoscope. We reviewed our experience with the use of the Nd: YAG laser in the fulguration of PUV and compared the results with a historical control group who had undergone the classical electrocoagulation of the PUV at our center.
| Material and Methods|| |
50 boys aged between 5 days and 4 years, diagnosed to have PUV by voiding cystourethrogram (VCUG) underwent cystoscopy on a day-care surgery basis under general anesthesia. The diagnosis was confirmed and Nd: YAG laser fulguration of the PUV was performed. The procedure was performed in the lithotomy position using the Wolf 8.5 cystoscope and the 25° telescope. This angled telescope helps to keep the laser beam under visual control throughout the fulguration. After identifying the valves, the 600µ quartz bare fiber of the laser is passed through the side channel of the cystoscope and brought in direct contact with the valves that were then fulgurated. The bare fiber was brought in contact with the central portion of the valves that were then vaporized advancing centrifugally. The laser power setting ranged from 25-30 Watts and the total energy delivered each time ranged from 160-756 Joules, with a meanof 316 Joules. No attempt was made to vaporize the valves all around completely so as to reduce the chances of laser injury to the surrounding structures. The adequacy of the fulguration was checked in the operating room by observing the urinary stream. The children were discharged after the procedure and reviewed at 3 months with VCUG. Follow-up extended from 2 months to 36 months with a mean of 18 months. Historical controls consisted of patients with PUV (n=50) who had undergone cystoscopy and electro-coagulation of the valves during the time period 1995-1997 at our institute.[Table 1]
| Results|| |
The mean age of children in the group treated by laser fulguration was 1.3 years (range: 5 days-4 years) while the mean age in the electrocoagulation group was 2.6 years (range: 5 months-6 years). Post-fulguration urinary stream was satisfactory in both groups at the operating room. In the electrocoagulation group, all the children were catheterized after fulguration and were hospitalized for a period ranging from 48 hours to 5 days and this was the protocol at our center. All the patients in the laser group were treated on an outpatient basis and were not catheterized. Three patients in the electrocoagulation group had hematuria in the postoperative period, which was self-limiting. Upon suspicion of poor stream of urine at the follow-up, check cystoscopy was performed in 5 patients belonging to the laser fulguration group and 4 patients in the electrocoagulation group and the valves were refulgurated with the respective modalities. These refulgurated patients underwent follow-up with VCUG at 3 months and showed no further evidence of residual valves. The profile of both the groups is depicted in the table. It is evident from this table that with the application of Nd: YAG laser the age profile has shifted towards younger age. This is due to the fact more and more younger patients are being offered the laser fulguration at an early age which is feasible with this modality.
| Discussion|| |
This study has shown that Nd: YAG is a good modality for fulguration of the PUV in children. In 1984, Nd: YAG was approved for the treatment of bladder cancer by FDA of USA and this has now expanded its role. It is now being used in the treatment of various urolgical conditions like intraurethral condylomata, transitional cell carcinoma, benign prostatic hyperplasia and urethral stricture disease. , The use of laser for fulguration of posterior urethral valves has been described in a few reports, , albeit in a small number of cases. The Nd: YAG laser offers an alternate modality for ablation of the valves, with a very high precision. This laser works by the various physical principles that interact between the tissue and the laser and is primarily determined by absorption - which is essential for the conversion of the light energy to thermal energy. With the contact of laser energy with the valves, the thermal effect is triggered, whereby the light energy is transformed to heat and consequently there is tissue denaturation followed by carbonization and tissue vaporization.  So the primary effects of Nd:YAG laser fulguration is the thermal ablation of the valves with negligible vaporization. This is similar to the electrocoagulation but the laser has lower penetration and surrounding injury if the pulse and the duration are modified to suit the needs. It has been shown that with the use of the laser there is slough formation and after this re-epithelialisation occurs without scarring or fibrosis.  Keiditsch et al performed animal experiments and it was reported that the Nd:YAG laser has the advantage of causing a circumscribed tissue necrosis with a well-defined depth, that is controlled precisely and is constant and reproducible as opposed to electrocoaguation which is less homogenous. 
It is important to keep the duration of the laser bursts to a short time so as to limit the extent of the injury and give the pause between the bursts so as to lower the overall energy delivered. Limiting the pulse duration of the laser to 0.2 seconds with intervals of 0.3 seconds permits the underlying tissue to spread thermal injury during the pauses, thus limiting the depth of tissue affected by the laser. Pulse duration < 0.2 seconds also greatly reduces the possibility of self-destruction of the fiber tip. The delivery of the laser as a pulsed mode of delivery instead of a steady continuous mode further helps as it allows a lower total quantity of energy with a higher peak power, improving the cutting characteristics of the device. Also, when the laser fiber is used in the contact mode, the fiber mainly causes tissue vaporization and seems to be the best choice for this purpose, with minimal extension of the energy into surrounding periurethral tissues.  Using electrocautery, a stricture urethra at the site of fulguration has been reported, with the incidence varying from 1-8%  to 8-25%. ,, With the high precision of the laser beam and the limited penetration of the energy when used in the contact pulsed mode, there is significant reason to believe that the rate of urethral stricture following laser coagulation will be significantly lesser. The reported damage to the sphincter and the subsequent urinary incontinence described after electrocoagulation  should be lesser with the laser. These theoretical advantages need to be corroborated by long-term follow-up studies.
The 8.5 cystoscope allows endoscopy of the urethra and bladder even in low-birth-weight infants. This is especially relevant in our setup where the substantial proportion of infants are of low birth weight and small for date in whom it was difficult to negotiate the 9.5 resectoscope available with us. The Nd: YAG laser beam is transmitted by advancing the 600µ bare fiber through the side channel of the cystoscope and this retrograde endoscopic laser application in the neonate is technically feasible, thus allowing early ablation of the valves. Early fulguration of the valves gives a chance for better bladder function and cycling. Many authors have stressed the better function and urodynamic characteristics of the bladder which has not been diverted compared to a diverted bladder. ,, The earlier the valves are ablated, the need for secondary procedures has been reported to be fewer. 
In conclusion, endoscopic laser fulguration of PUV is technically feasible even in neonates and small children. It offers excellent results that are comparable to the timehonored electrocoagulation, with an additional advantage for fulgurating the PUV in smaller caliber urethra as this can be performed with the smaller available cystoscope that has a side channel. However, long-term studies are indicated in evaluation of strictures, ejaculatory abnormalities and continence after fulguration with the Nd: YAG laser as the studies with this new modality are few and only short-term results have been reported.
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