New device for visual neodymium:YAG laser prostate ablation: Acute and chronic canine evaluation

This canine study (n = 6) evaluated the acute and chronic effects of Nd:YAG laser prostatectomy using a Prolase II fiber. The Prolase II device consists of a 1,000 μm quartz fiber which directs a cone of Nd:YAG laser energy, at 45° to the axis of the fiber, into the prostatic urethra under direct visual guidance [visual laser ablation of prostate, (VLAP)]. Under visual guidance and saline irrigation, 60 seconds of 60 watts of laser power was delivered at 3, 6, 9, and 12 o'clock positions (14,400 J). One canine was instrumented but received no laser energy (control). One prostate was harvested acutely. The remaining four laser-treated dogs were evaluated at 6 to 16 weeks. The histopathology of acute laser effects shows areas of necrosis with loss of glandular structures and stromal edema. Surrounding this area was a zone of degenerative glandular structures extending up to 12.6 mm into the prostate. Two of the four dogs developed urinary retention at 6.5 and 9 weeks. On examination, both were found to have fibrotic strictures at the distal prostatic urethra with markedly dilated proximal prostatic urethral lumens (1.98 and 2.8 cm). Two other dogs showed no signs of urinary retention at sacrifice. Histopathology, both the 6 and 16 week laser-treated animals without urinary retention demonstrated dilated prostatic urethras with maximum cross-sectional diameters of 1.52 and 1.50 cm, respectively. However, the 16 week dog demonstrated mild distal urethral narrowing by urethrogram. The control dog demonstrated normal histology of the prostate at 16 weeks. This study demonstrates the safety and initial results of a delivery device for trans-urethral laser prostate ablation in a canine model. Further studies are needed to evaluate the cause of the fibrotic urethral strictures in this model and determine its clinical relevance. © 1994 Wiley-Liss, Inc.     

Thermal changes in the canine prostate after transurethral balloon laser prostatectomy

The histological changes by transurethral balloon laserthermia were examined on 23 canine prostates. Immediately after treatment, three zones were observed; the coagulative zone treated over 60°C for 20 min formed an inner layer, the degenerative zone treated between 60 to 46.1°C surrounded the coagulative zone, and the intact zone treated below 46.1°C formed the outer layer. Coagulative necrosis of the gland, swelling of collagen fibers, and thrombus of the vessels occurred in the coagulative zone, shedding and vacuolation around the nuclei of the epithelial cells and stromal edema were observed in the degenerative zone, while thermal changes were minimal in the intact zone. Both coagulative and degenerative zones developed necrosis and started to slough off within 1 week, forming a cavity in the central portion of the prostate. Reepithelialization of the cavity was complete at 4 weeks and the ducts of the prostate gland opened to the surface of the cavity. This treatment preserved the excretory tract of the prostate gland. © 1994 Wiley-Liss, Inc.     

Transurethral Balloon Laser Prostatectomy in the Canine: Medium-Term,Follow-Up Results

Background and Objective: To demonstrate surgical complications in transurethral balloon laser prostatectomy by medium-term, follow-up observation. Study Design/Materials and Methods: Three dogs were treated with transurethral laser irradiation using 15 watts for 20 minutes at 60°C at a 5 mm depth of the prostate, one dog was for 5 minutes with same parameters, and one dog was with only laser balloon probe as a control. All animals were followed for 24 weeks. Results: A large cavity in the prostatic urethra was formed in laser-treated animals 4 weeks later, whereas the cavity in the balloon-treated animals was not shown. Cavity volume did not significantly change for 6 months, and there was no bladder neck stricture or urethral stenosis observed in any case. An increase in collagen fibers in the periurethral tissue was barely observed by Mallory staining. Conclusion: The risk of bladder neck stricture and urethral stenosis was estimated to be low for transurethral balloon laser prostatectomy. © 1995 Wiley-Liss, Inc.     

Characterization of tissue effects produced by the Prolase II lateral-firing neodymm:YAG laser fiber in the canine prostate

The immediate and long term-effects of neodymium:YAG laser treatment with the ProLase II lateral-firing laser fiber in the canine prostate were evaluated. Fourteen male dogs, aged 3 years and older with established benign prostatic hyperplasia, underwent endoscopic ablation of the prostate using the ProLase II fiber. Subjects were treated at laser power settings of 60 watts (6 dogs), 75 watts (4 dogs), or 90 watts (3 dogs), with a mean total energy delivery of 15,000 joules. One dog underwent a sham procedure and served as a normal control. Prostates were examined grossly and histologically at 48 hours, 2 weeks, 4 weeks, or 8 weeks post-treatment. The cross-sectional diameter and volume of tissue ablation were measured in each prostate. Histological studies of the extent of thermal injury to the prostatic tissue and the course of healing of the prostatic urethra were performed. The mean cross-sectional diameter of tissue ablation was 28.6 ± 4.7 mm and mean volume of tissue ablation was 8.2 ± 5.1 cc. No statistically significant difference in diameter or volume of tissue ablation was noted between varying power settings. Histological studies showed extensive tissue necrosis with hemorrhage and an acute inflammatory cell infiltrate at 48 hours. By 8 weeks, total resolution of both necrosis and inflammatory changes with complete re-epithelialization of the prostatic urethra was observed. © 1994 Wiley-Liss, Inc.     

Pathologic changes occurring in the prostate following transurethral laser prostatectomy.

Serial gross and histopathologic examinations of the prostate following transurethral laser prostatectomy in the canine model demonstrated an immediate well-demarcated sphere of thermal necrosis measuring 2.7 cm in diameter, which, within 24 hours, had begun liquefaction and was showing multiple areas of cavitation. By the end of the 1st week, the areas of cavitation had coalesced to form a central cavity lined by a narrow layer of necrotic tissue clinging to the thin surviving peripheral belt of prostatic glandular parenchyma. At 3 weeks, the bluish-black discoloration resulting from breakdown of blood in the necrotic tissue had subsided, leaving masses of coagulonecrotic tissue within the central cavity. Within 5 weeks, the ectatic central cavity was lined by transitional epithelium. These postmortem pathologic observations confirm our surgical and clinical impressions of being able to satisfactorily perform an effective transurethral prostatectomy using neodymium:YAG (Nd:YAG) laser photoirradiation.     

Holmium: YAG Laser Resection of the Prostate Versus Visual Laser Ablation of the Prostate and Transurethral Ultrasound-Guided Laser Induced Prostatectomy: A Retrospective Comparative Study

Background:
Transurethral resection of the prostate (TUR-P) is the gold standard for treating symptomatic benign prostatic hyperplasia (BPH) despite some perioperative morbidity. As a minimally-invasive alternative to TUR-P, a neodymium:YAG laser, and more recently a holmium:YAG laser, have been used in transurethral surgery for BPH. In order to assess the safety and efficacy of various BPH treatments, the outcome in patients treated with transurethral ultrasound-guided laser induced prostatectomy (TULIP), visual laser ablation of the prostate (VLAP) and holmium:YAG laser resection of the prostate (HoLRP) were retrospectively compared.
Methods:
From May 1995 to August 1996, 60 patients with symptomatic BPH underwent TULIP (n=20), VLAP (n=20), and HoLRP (n=20). All patients were evaluated preoperatively and at 1 and 3 months postoperatively by the International Prostate Symptom Score (IPSS), the IPSS quality-of-life score (QOL), maximum flow rate (MFR), prostate volume, and residual urine volume.
Results:
The preoperative mean IPSS was 18.5, 19.3, and 19.6 and the mean MFR was 6.3, 6.9, and 6.1mL/sec in the TULIP, VLAP, and HoLRP groups, respectively. At 1 month after surgery, the mean IPSS was 10.2, 9.5, and 4.7 and the mean MFR was 9.6, 1 3.4, and 1 8.7mL/sec while at 3 months the mean IPSS was 6.2, 6.1, and 3.6 and the mean MFR was 14.1, 1 6.0, and 21.5 mL/sec in patients treated with TULIP, VLAP, and HoLRP, respectively. No serious complication occurred in any patient.
Conclusion: Although HoLRP requires expertise, it appears to be a promising treatment modality for BPH.     

Endoscopic laser therapy for the treatment of malignant esophageal obstruction

Malignant esophageal obstruction in 24 patients was treated using the neodymium:ytrium, aluminum, garnet laser. There were 15 males and nine females; the average age was 70.9 years. There were 17 adenocarcinomas and seven squamous cell carcinomas, with two of these being recurrent after radiation therapy. Tumor lengths ranged from 2.5-19.0 cm, with an average of 6.7 cm. The average energy delivered per centimeter of tumor was 6,309 joules for the squamous cell carcinomas and 5,598 for the adenocarcinomas. Energy delivered per treatment ranged from 3,152 to 70,527 joules. Total energy delivered per patient depended on the volume of tumor destroyed. Esophageal lumens increased from 3.4 to 16.7 mm, and 23 patients had their diets advanced, 22 to regular and one to soft solids. Reobstruction did not occur in patients who received adjunctive therapy after laser therapy. This consisted of chemotherapy in five, surgery in two, and radiation therapy in one. Complications consisted of aspiration pneumonia in three patients, including one who developed a tracheoesophageal fistula, and one documented and two suspected perforations. Hospital stay averaged 5.4 days overall and 3.5 days in those treated with the single-session technique. This increased to 8.0 days in patients with proven or suspected perforations. Endoscopic laser therapy is a safe and effective method for palliating esophageal cancer.     

Transurethral laser prostatectomy in the canine model

A technique for performing transurethral prostatectomy was devised using a Neodymium:Yttrium Aluminum Garnet laser in a canine model. Six dogs underwent transurethral laser prostatectomy following establishment of a perineal urethrostomy. The efficacy of the prostatectomies was judged by retrograde urethrography, transrectal prostate ultrasonography, cystoscopy, and histologic examination. The method of applying laser energy while holding the tip of the fiberoptic light guide 2–3 mm away from the prostate was ineffective; with power ranging from 40 to 70 watts, this technique resulted mainly in coagulation necrosis and removal of only a small amount of tissue. However, placing the tip of the light guide in direct contact with the prostate and using power from 70 to 100 watts produced impressively large prostatectomy defects by tissue vaporization. We conclude that this newly devised technique for transurethral prostatectomy in the canine model can be performed safely and effectively using a Neodymium: Yttrium Aluminum Garnet laser (Neodymium:YAG).     

Ureteroscopic management of transitional cell carcinoma of the ureter using the neodymium:YAG laser

Ureteroscopy offers an extension of endoscopic diagnosis and treatment to upper urinary tract malignancy. Combination of ureteroscopy and the Nd:YAG laser permits accurate and effective treatment of ureteral neoplasms. Nine highly selected patients, six males and three females, were treated with low grade papillary transitional cell carcinomas of the ureter with at least 24 months follow-up. Follow-up cytology and IVP have indicated no evidence for disease recurrence between the follow-up periods and minimal morbidity to the ureteroscopy and laser treatment. © 1993 Wiley-Liss, Inc.     

Thulium:yttrium‐aluminium‐garnet laser prostatectomy in men with refractory urinary retention

OBJECTIVE

To evaluate the feasibility and efficacy of thulium:yttrium‐aluminium‐garnet (YAG) laser prostatectomy in patients with an indwelling transurethral catheter due to recurrent urinary retention secondary to benign prostatic obstruction.

PATIENTS AND METHODS

Preoperative data and postoperative outcome, as well as complications, were recorded in 65 patients with a history of recurrent urinary retention before surgery (group A), who were compared with a group of 143 men with no recurrent urinary retention (group B).

RESULTS

The mean (sd ) volume of the prostate was 45.6 (22.5) and 43.1 (24.5) mL in groups A and B, respectively. The respective preoperative prostate‐specific antigen levels were 3.6 (7.8) and 2.8 (6.4) ng/mL, the surgical duration 72.4 (28.9) and 65.6 (28.6) min, the mean laser time and energy 32.5 (11.8) min/140.7 (42.1) kJ and 29.4 (11.6) min/117.6 (11.6) kJ, the maximum urinary flow rate after surgery 19.6 (11.2) and 19.1 (9.6) mL/s, and the postvoid residual urine volume 26.7 (36.3) and 20.6 (27.3) mL. Recorded complications were: bleeding, at 3% in group A and 1.4% in group B; urinary tract infection 15.4% and 4.2%; and a second procedure, 3% and 2.3%. Overall, complications were more frequent in group A (P = 0.02).

CONCLUSION

Thulium:YAG prostatectomy is feasible and effective, even in patients with potentially impaired detrusor function. The long‐term durability of these promising results has yet to be confirmed.     

Nd:YAG laser irradiation to intraluminal mass lesions of the superior vena cava under laser balloon angioscopy in an experimental canine model

A laser balloon angioscopic procedure was developed in a canine model for intraluminal mass lesions in the superior vena cava, using an endoscope bearing a very thin balloon through which Nd:YAG laser could penetrate. The balloon was made from artificially modified natural latex rubber and well expanded with saline infused through a biopsy channel. The endoscopic image of the object obtained through direct contact of the balloon expanded with saline was clear enough to observe the internal surface or branches in not only normal, but also pathological conditions of the canine SVC. The Nd:YAG laser was able to be successfully irradiated through the balloon using this procedure which, although still in its preliminary state, may be a useful clinical, diagnostic and therapeutic tool of the future.     

Ablation of bone and methacrylate by a prototype mid-infrared erbium:YAG laser

An erbium:YAG laser was used to generate 200-microseconds pulses of mid-infrared 2.94-microns light in both the single and multimode configurations. Laser pulses were focused on the surfaces of both rabbit long bones and methacrylate blocks, and the tissue response was examined histologically. The depth of thermal injury was determined by ocular micrometry. Over all energy levels tested, the erbium:YAG laser produced ablation of bone and methacrylate with minimal thermal damage to adjacent tissue. Increasing the laser energy per pulse produced increasingly wider and deeper grooves in both bone and methacrylate. However, such increase in laser energy produced a proportionately greater increase in the zone of thermal injury in methacrylate as compared with bone. These studies suggest the feasibility of a surgical erbium:YAG laser in orthopaedics and other forms of ablative surgery.     

Long-term results of high-power holmium laser vaporization (ablation) of the prostate

OBJECTIVE: To present the 7-year follow-up data from the initial series of patients treated by holmium laser ablation of the prostate (HoLAP) for symptoms of benign prostatic hyperplasia at our institution. PATIENTS AND METHODS: In all, 79 patients underwent HoLAP in the initial series between September 1994 and May 1995. All patients were contacted by telephone and mail; those available for follow-up had their peak urinary flow rate, American Urological Association (AUA) symptom score, single-question quality-of-life (QoL) score and adverse events assessed. Patients were also assessed using the International Continence Society 'male short-form' (ICSmaleSF) questionnaire on lower urinary tract symptoms (LUTS). RESULTS: At a median follow-up of 89 months (7.4 years), 17 patients had died (21%), 28 could not be contacted or refused follow-up (35%), leaving 34 patients (43%) available for assessment. The mean (range) AUA score of the remainder was 10.0 (0-26), the maximum urinary flow rate 16.8 (5-35) mL/s and QoL score 2.1 (0-5). The mean ICSmaleSF voiding score was 5.8 and the mean incontinence score 3.2. The impact score of their current LUTS (QoL) was 0.68, implying a minimal effect. No patient required pads for incontinence. The reoperation rate was 15%, with one patient each undergoing transurethral resection or bladder neck incision, two undergoing holmium laser enucleation of the prostate and one having a bladder stone removed endoscopically. CONCLUSIONS: The long-term results of HoLAP were satisfactory in those patients who were available for the follow-up.     

Preliminary study of the Nd:YAG laser in canine partial nephrectomy

Partial nephrectomy is effective in the treatment of segmental renal disease but hemostasis remains a challenge. In this preliminary investigation the Nd:YAG laser was used alone or as an adjunct to the scalpel in partial nephrectomies to determine if hemostasis could be improved. A technique of 100-W laser transection with occlusion of the renal artery was effective for partial nephrectomy and achieved complete hemostasis. Conditions of patent renal artery flow or renal cooling were associated with a reduction in necrosis depth with 100-W laser partial nephrectomies. All techniques were compatible with survival over the 5-day study period.     

A 4-year follow-up of a randomized prospective study comparing transurethral electrovaporization of the prostate with neodymium: YAG laser therapy for treating benign prostatic hyperplasia

OBJECTIVE: To compare the safety, efficacy and durability of neodymium (Nd):YAG laser prostatectomy with transurethral electrovaporization of the prostate (TUVP) for treating benign prostatic hyperplasia (BPH). PATIENTS AND METHODS: From March 1995 to March 1997, 180 patients with bladder outlet obstruction secondary to BPH were randomized equally either to Nd:YAG laser therapy or TUVP. Laser therapy combined two different techniques, side-fire coagulation of the lateral lobes and contact vaporization of the median lobe. Before treatment the two groups had a comparable International Prostate Symptom Score (IPSS), quality-of-life score (QoL), maximum urinary flow rate (Qmax), postvoid residual urine volume (PVR), and prostate and adenoma volume. In all, 62 and 78 patients completed the 1, 2, 3 and 4-year follow-up from the laser and TUVP groups, respectively. RESULTS: At each follow-up, the IPSS, QoL, Qmax and PVR were significantly better and more durable in the TUVP than in the laser group. In the TUVP and laser groups respectively, at the 4-year follow-up the mean value of the IPSS was 3.7 vs 11.9, the QoL 1.3 vs 3.1, the Qmax 21.4 vs 13.6 mL/s and the PVR 25.1 vs 64.6 mL (all P < 0.001). The mean prostate and adenoma volume were significantly lower after TUVP than after laser therapy (P < 0.001) at the 1- and 4-year follow-up, with final values of 27.9 vs 35.9 and 11.7 vs 20 mL (both P < 0.001) for the TUVP and laser groups, respectively. Retrograde ejaculation was significantly more common after TUVP (63%) than after laser therapy (18%; P < 0.001). Impotence was reported in 8% of men after TUVP and in none after laser therapy (P = 0.040). The re-operation rate was 12% after TUVP and 38% after laser treatment (P < 0.001). CONCLUSION: These 4-year follow-up results confirm that TUVP is significantly more effective and durable than the Nd:YAG laser for treating BPH. Residual obstructing adenoma was the main cause of failure in the laser group, which reflects the inadequacy of laser therapy for removing the adenoma.