sabato, 24 febbraio 2024
8 Giugno 2002


Dependent on the laser wavelength or it’s penetration depth, respectively, and the power density, which is a function of laser output power, applicator size or beam divergency and distance between applicator and irradiated surface, and application technique, the resulting tissue effect is either coagulation or vaporization. Coagulation can be achieved by superficial or interstitial laser application. Vaporization can occur using free beam or contact laser irradiation and can be broad, which is called ablation, or narrow, which is called incision, when the applicator is moved. Two or more incisions
connected with each other result in a resection of tissue or enucleation, respectively, if the whole adenoma is removed.
Interstitial laser coagulation: In contrast to the free beam laser irradiation approach, the objective of ILC is to achieve coagulation necrosis inside the adenoma, rather than at its urethral surface. The interstitial coagulation results in secondary atrophy and regression of the prostatic lobes. This is in contrast to the sloughing of necrotic tissue which occurs after free beam coagulation. Both Nd:YAG and diode lasers can be used for ILC because of their relatively deep penetration in water, efficient volumetric tissue heat loading, and the ability to be delivered through flexible optical fibers. The goal of creating the largest coagulative volume in the shortest amount of surgical time is accomplished by initiating irradiation with a relatively high power to rapidly heat the tissue and coagulate the blood vessels, followed by laser power reduction in order to maintain the temperature in the center of the lesion at a high level just below the carbonization threshold, and allow further lesion expansion. Therefore, the optimal irradiation parameters vary for different laser wavelength and applicator combinations. On-line temperature monitoring by an integrated thermocouple allows further optimization by use of a power feedback control, and optical feedback systems can detect carbonization. This prevents overheating and fiber damage as well as the tissue char which would limit laser penetration. The learning curve of ILC is short, however, ILC is a surgical technique and requires a correct fiber placement to be successfully performed.
Transurethral holmium laser enucleation: This procedure is similar to a standard transurethral electroresection of the prostate, because the prostate tissue is resected. The procedure is usually performed with a holmium:YAG laser and a bare fiber, but was also done using a Nd:YAG laser with a bare fiber as well as a special contact tip (in recent times, this type of resection was even done using a simple electrosurgical device, without employing a laser). In holmium laser enucleation of the prostate (or “electrodissection”, respectively), two incisions are performed in the 5 and 7 o’clock positions from the bladder neck through to the verumontanum down to the capsule. At the level of the veru, the incisions are connected with each other. The middle lobe is then enucleated in toto by dissecting it from the capsule. The resection starts at the veru and commences towards the bladder until it is finally cut off. Next steps are incisions in the 11 and 1 o’clock positions and a curved incision along the external sphincter on each side to connect the dorsal and ventral incisions, open the plane between the side lobes and the capsule at the apex and begin the enucleation of the side lobes. This is finalized the same way as the middle lobe is resected. Besides a long learning curve to perform the procedure, the problem is to remove the big tissue pieces from the bladder. This usually requires a tissue morcellator, which can cause potential complications, is time consuming and costly. However, because the enucleation is performed in one single plane, there is almost no bleeding during the procedure resulting in a far lower complication rate compared to TURP with the same efficacy as TURP because the tissue is removed completely and immediately.
In the past years, many studies have proven the clinical efficacy of the mentioned laser treatments of BPH including randomized studies versus TURP. Urodynamic controls confirmed that an effective unobstruction was achieved. In recent studies, long-term follow-up of up to 5 years have demonstrated the durability of the results, although in some of the studies, retreatment rates were higher than after TURP.
Limitations of the techniques must be taken into account. In all coagulation techniques, not only those using laser technology, an initial increase of obstruction due to the heat associated edema and tissue hardening must be expected. The volume reduction does not occur immediately, but delayed. This requires postoperative catheterization for days or weeks, according to the detrusor function. These problems are not shared by the laser vaporization and resection techniques. However, these are difficult to learn, and require
usually a long operation time.
Laser treatment of BPH has left its infancy and has matured. For good clinical results, however, the user needs to accept the requirements of success which is proper training. It is not only important to know the basics of lasers and laser-tissue interaction. It is mandatory to understand the procedure, and to use the adequate technology and adequate surgical technique.